Integrate more native species in reforestation efforts

Although governments have a long history of finan-
cially supporting reforestation of abandoned agri-
cultural lands—or lands where declining productiv-
ity implies that abandonment will be likely—their
efforts have too often favored forest plantations. To
achieve a better carbon balance, more biodiversity,
and better forest protection from pests, storms, and
fires, governments should support more regrowth
of native species, as South Korea, among other
countries, is now doing.¹²²

Actively support farmer-assisted regeneration

Many farms include areas that are unsuitable for food production but where occasional cattle grazing or the spread of fires are enough to block tree regrowth. Farmer-assisted natural regeneration can occur in these conditions if soil, water, and climate are suitable for natural recovery, and if competing productive uses of the land are low. Another requirement is that native source populations for

trees exist, for example, tracts of remnant natural
forest, or root stocks of native trees.

We suggest that governments create programs to support farmer-assisted regeneration by specifically including regeneration in existing policy efforts:

- **Traditional agricultural loans.** Integrate lines of concessional credit to restore trees on marginal lands (e.g., poor soils, slopes, riparian areas) into traditional loans.

- **Farmer outgrower schemes.** Embed tree restoration in outgrower schemes, which combine multiple restoration success factors in one package: they provide seeds and seedlings, technical assistance, financing, and champions or leadership.

- **Tenure laws.** Reform tenure and titling laws (as discussed in Chapter 35) to assure farmers that, if they regenerate trees, they will be able to benefit from them.

BOX 20-1 | Why Estimates of Reforestation Potential Tend to Be Too Optimistic

Although the potential for reforestation is
real and might be further increased with
successful efforts to hold down the rate
of growth in demand for food and boost
yields, reforestation potential today is
typically overestimated. Good policymaking
depends on understanding why.

The economic costs of reforestation
are typically gauged by estimating the
costs of using land to plant trees that will
sequester carbon. In such an approach,
reforestation potential in any of the vast
areas of agricultural land that occupy land
where forests once existed is just a matter
of price.

The most common method to estimate the
cost of using land is simply to value land at
its rental value and then to add the costs of
planting and maintaining trees.ª Although
often incorporated into more elaborate
models, the costs of carbon sequestration
equal rental value and the annualized value

of these other costs divided by the tons
of carbon that can be sequestered each
year. For example, if the rental value of a
hectare of cropland is $100, and it would
be possible for trees to remove 10 tons of
carbon dioxide per hectare each yearª then
the land-use cost is $10 per ton of carbon
dioxide removed. (For simplicity, we ignore
planting costs in this example.) So long as
people value climate mitigation at $10 per
ton, this method would therefore conclude
that it is economical to restore forest on
this hectare of cropland.

Unfortunately, the rental price of land
does not reflect the true cost of both
sequestering carbon and meeting all food
needs. Rather, the rental value reflects
what farmers would pay to use land in
one way, compared to the next cheapest
market alternative, which includes actions
that release carbon or diminish production.
For example, one alternative to renting

any hectare of land might be that farmers
clear another hectare of land instead.
Overall, farmers will only pay rent to use
existing agricultural land if the cost is less
than the cost of producing the same crops
by clearing more land. For this reason,
the cheaper it is for farmers to clear new
land, the lower the rental value of existing
agricultural land. Yet clearing other land
releases carbon, which undermines
the carbon sequestration benefits of
reforestation. An irony of using the rental
value method is that, the cheaper it is for
farmers to clear more land, the more likely
they are going to respond to reforesting
one hectare of cropland by clearing
another, which would reduce—and could
eliminate—net gains in carbon storage. For
this reason, rental values should not be
used to estimate the costs of gaining net
carbon sequestration benefits by taking
land out of production.
BOX 20-1 | Why Estimates of Reforestation Potential Tend to Be Too Optimistic (continued)

Perhaps worse, rental values also are limited by the ability and willingness of people to pay for food. When land is taken out of production, some consumers will not be able or willing to pay the resulting higher prices for food and food consumption will decline. In fact, the more price-sensitive is food consumption, the lower will be the agricultural rental value. Again, lower rental values do not necessarily reflect a lower cost of restoring forests while still meeting the same food demands but rather may reflect a larger reduction in food consumption.c

In summary, while agricultural rental values do reflect the financial cost of restoring a particular hectare of land, they do not reflect the cost of sequestering carbon on a net basis or doing so while still supplying the same global quantity of food.

Removing some land from production may sometimes lead, through higher food prices, to some desirable results, such as reduced consumption by the wealthy of ruminant meat or reduced food loss and waste. But because any such effects occur through generalized increases in food prices, those same higher prices will also reduce food consumption by the poor, and will probably do so disproportionately because the poor are less able to afford higher prices. d The higher prices will

also encourage farmers to expand crop area. Taking good agricultural land out of production for the purpose of reforestation is not therefore generally either an equitable or effective strategy for reducing undesirable consumption.

Even when underlying models to some extent reflect these issues, their results can easily be taken out of context and therefore fail to explicitly convey the conditions necessary for reforestation. For example, Griscom et al. (2017) suggest that there is potential to reforest millions of hectares of grazing land. They cite two modeling studies to support the proposition that this reforestation would be possible without sacrificing food production. One of these studies assumes that reforestation occurs only on abandoned agricultural land. Although this paper (using the IMAGE model) does not explain why abandoned land becomes available, the land apparently becomes available only between 2050 and 2100. In other IMAGE modeling papers concerning this period, the abandoned land becomes available as a result of assumptions about limited population growth and high rates of yield gains. The other modeling study estimates that the level of additional land-clearing could be reduced at carbon prices up to $100 per ton of carbon dioxide, in part by

intensification of grazing systems, and in part by reductions in consumption of livestock products. This second study tries to estimate what would happen if the cost of climate change at different carbon prices were built into all food production and consumption decisions, so that farmers would be taxed to produce beef and other livestock products, people would pay those taxes when they consumed, farmers would also be rewarded for reforesting their land instead of producing food, and other farmers would be persuaded not to clear more forest in response because clearing would be taxed. Thus, the preconditions for reforestation potential in both studies are substantial. In one study, the condition is a net decline in agricultural land. In the other, stringent global policies are enacted to boost yields, protect existing forest, and discourage consumption of livestock products.

In effect, these conditions represent one way in which a global economic model can simulate successful adoption of many of the recommendations of this report to protect natural areas and reduce demand for agricultural land. As such, these estimates only reaffirm that large-scale reforestation depends on successfully implementing the various menu items in this report.

Notes and sources:

a. Examples of such efforts include Benítez et al. (2004) and a special paper prepared for the "Stern Report," published in updated form as Grieg-Gran (2008). In Benítez et al. (2007), the authors excluded more productive cropland but estimated sequestration costs based on the return to other agricultural land. In van Kooten and Sohngen (2007), the authors reviewed a wide range of studies and analyses and, although they did not describe all the studies in depth, none of the studies were described as focusing on the cost of meeting alternative food supplies on other land and instead were described, at most, as focusing on the opportunity cost of land, which we read as involving the economic return to land for alternative uses at present prices. The studies we have been able to analyze that use economic models also often incorporate this error although sometimes not technically using rent but net agricultural return, which is a way of estimating rent. In Sathaye et al. (2011), for example, the agricultural value of a hectare of land is estimated (and very roughly) by the price of the crops that could be grown minus the costs. In Sohngen and Sedjo (2006), the price of agricultural land is fixed at its rental value, which also effectively means the price of a crop reflects (a) the costs of producing it, including by clearing more land, and (b) the willingness or ability of consumers to pay for it. Therefore, the cheaper the supply of new cropland, and the larger the consumer response to prices, the cheaper the price of crops, and the lower the opportunity cost of using land. Economic models can attempt to get at the carbon costs of equilibrium. At a fundamental level, even equilibrium models are estimating net agricultural returns to land. The reason land receives an economic return is only because the cost of producing food on that land is less than the cost of clearing new cropland, growing food on that land, and transporting that food to consumers, or is less than the price consumers are willing and able to pay.

b. That level of carbon dioxide equals 2.7 tons of carbon per hectare per year, which is a reasonable figure for much reforestation.

c. Many economic models in fact estimate a large food reduction effect from diverting agricultural land to other uses, as discussed in our chapter on bioenergy.

d. Regmi et al. (2001); Muhammad et al. (2011).

e. Strengers et al. (2008).

f. Havlík et al. (2014).
<figure><img src="image_136.png" /></figure>
MENU ITEM: CONSERVE
AND RESTORE
PEATLANDS

Only a small portion of the world's agricultural land sits atop peat, but these areas have large impacts on climate change—contributing as much as 2 percent of total annual human-caused GHG emissions, according to our calculations. Given this disproportionate impact, a dedicated effort is needed to avoid any further conversion of peatlands to agriculture and to restore some of the world's peatlands that have already been drained for crops or livestock.
## The Challenge

According to one estimate, peatlands¹²³—the most carbon-rich category of wetlands—occupy around 450 Mha of land, or roughly 3 percent of the ice-free terrestrial land surface, yet they store 450 to 600 gigatons of carbon.¹²⁴ This quantity is equal to between 60 and 80 percent of carbon in the atmosphere (and around one-quarter of all the carbon stored in global soils). Peatlands form because they are located in landscapes that retain moisture and thus have almost permanently saturated soils. The water blocks the penetration of oxygen, which is needed by most bacteria to break down biomass and release the carbon in dead plant material back into the air. As a result, peatlands can build up large deposits of carbon, sometimes over tens of thousands of years. Although grasslands and forests are generally believed to stabilize at maximum levels of soil carbon, peatlands, if undisturbed, tend to continue to build carbon in soils indefinitely. In the tropics, peatland carbon accumulation rates can reach 0.4 tons per hectare per year.¹²⁵

Growing crops on peatlands typically requires draining them so that oxygen can penetrate soils and reach plant roots. (Although plants release oxygen when they photosynthesize, they need oxygen to metabolize sugars into energy just like animals, and this oxygen nearly always comes through the roots.) Drainage leads to a release of carbon to the atmosphere because the oxygen stimulates the activity of bacteria and other microorganisms that break down organic matter, and because dry peats are prone to fires, whether naturally occurring or set intentionally. The amount of carbon released and the propensity to lose carbon through fire depends on the depth of the peat, the incidence of drought in the area, and the depth of drainage (the deeper the drainage, the more peat that is exposed to microbial activities or that becomes dry enough to burn).

Although two-thirds of peatlands are in climates cold enough to be affected by permafrost, the deepest peat deposits occur in the 13 percent of global peatlands that are located in the tropics, where the combination of high, year-round plant production and saturated soils leads to large annual peat deposits. The best documented, largest expanses of tropical peatlands occur in Southeast Asia, particularly Indonesia and Malaysia, where they have

typically supported dense rain forests.¹²⁶ In recent decades, these forested peatlands have been subject to large-scale, continuous drainage and clearing for agriculture and forestry. According to one analysis,¹²⁷ of the 15.7 Mha of peatlands in Malaysia and Indonesian Sumatra and Kalimantan,¹²⁸ only 6 percent (1 Mha) remained in relatively pristine condition as of 2015, and only 40 percent remained in some kind of natural forest (including forests regrowing after full clearing due to forestry activities). In contrast, 50 percent had been converted to use for agriculture or forest plantations. Forested peatland area declined by 1.8 Mha between 2007 and 2015 alone.¹²⁹

Based on our own mapping analysis, we estimate that 20 Mha of cropland, globally, is located on peat; we assume that almost all of this area is probably drained.¹³⁰ FAO similarly estimates that 18 Mha of peatlands are both drained and used for cropland, while 8 Mha are drained and used for pasture (Figure 21-1).¹³¹

Climate assessments originally did not pay much attention to emissions generated by these drained peatlands, but massive fires in Southeast Asian peatlands in 1997, 2007, and 2015 have attracted increasing global attention to the issue. Climate change estimates began to incorporate peatland emissions from this region (Figure 21-2), and more recently they have included estimates of peatland emissions from other countries (Figure 21-3). Amazingly, these tiny fractions of global cropland (roughly 1 percent) and pasture (roughly 0.3 percent) generate emissions typically estimated in the range of 1 gigaton of CO₂e per year, or almost 10 percent of annual emissions from agricultural production and associated land-use change.¹³²

We developed our own estimate to ensure use of the most up-to-date maps of cropland area, peatlands, and emission factors, and to enable a specific focus on peatlands in agricultural use.¹³³ We estimate ongoing annual emissions at a total of 1,103 Mt CO₂e, of which 863 Mt result from microbial decomposition and 240 Mt (annual average) from fire. These emissions amount to roughly 2 percent of all anthropogenic emissions from all sources, and roughly 9 percent of 2010 emissions related to agriculture. These emissions will continue for decades unless the peatlands are rewetted.
<figure><img src="image_137.png" /><figcaption>Figure 21-1 | FAO estimates that 26 million hectares of peatlands are drained and used for agriculture</figcaption></figure>

Source: Biancalani and Avagyan (2014), Figure 2.2.

<figure><img src="image_138.png" /><figcaption>Figure 21-2 | Greenhouse gas emissions from drained peatlands are ongoing in Indonesia and Malaysia</figcaption></figure>

Source: WRI (2017a).
<figure><img src="image_139.png" /><figcaption>**Figure 21-3** | Southeast Asia accounts for the majority of peatland emissions</figcaption></figure>

Note: Graph shows the top 10 countries associated with annual GHG emissions from drained peatlands.

Source: Biancalani and Avagyan (2014), Figure 2.5.

These estimates of emissions from peatlands may be too low if we are underestimating peatland area. Datasets are highly varied because global field mapping is limited, and satellite imagery provides only limited guidance. Researchers recently used a variety of methods to estimate where peatlands should form, backed by some reasonably successful ground validation, and estimated tropical peatlands at 170 Mha, roughly three times the predominant previous estimates.¹³⁴ This study estimated much larger peatland areas in Latin America and Africa. Around the same time, a separate group of scientists reported discovery of the world's largest tropical peatland in the heart of the Congo rain forest in central Africa.¹³⁵ They estimated that it stores 30 gigatons of carbon, equivalent to roughly 20 years of U.S. fossil fuel emissions. Discoveries of more peatlands may lead to more estimates of drained peatlands and therefore higher estimates of existing emissions. These estimates show the potential for a much greater risk of additional emissions from agricultural expansion in the future. To date, relative land abundance in both Latin America and Africa has reduced the need for investment in drainage of peatlands and other wetlands. But the history of Europe, the United States, and China suggests that as countries develop they tend to drain much of their wetlands for agriculture.

## The Opportunity

GHG emissions from peatlands will generally stop if peatlands are rewetted. Going further and restoring forests on naturally forested areas provides additional opportunities for sequestration. The precise techniques for rewetting vary by peatland, but they typically involve blocking drainage ditches and canals. In some situations, restoration may be more complex because roads or dams obstruct movement of water or divert water to other uses. Because peatlands shrink in elevation when drained, one complication typically involves rewetting peatlands to just the right level and avoiding too much flooding, which would prevent vegetation from regrowing. Still, even imprecise rewetting can avoid the ongoing degradation of peat.¹³⁶

Globally, there are many relatively small-scale examples of successful peatland restoration projects. One project rewetted 36,000 ha in Belarus at a 10-year cost estimated at $5 million, or $140 per hectare.¹³⁷ A project in China has restored water to tens of thousands of hectares in the 2 Mha of drained peatlands on the Ruoergai (or Zoige) Plateau on the northeastern margin of the Qinghai-Tibet Plateau. Another prominent example in the United States involved the government purchase and rewetting of tens of thousands of hectares of agricultural land in an area that occupied one-quarter of Florida's Everglades. After a protracted
lawsuit and political controversy, restoration began
as a means of filtering out phosphorus pollution
from the remaining agricultural lands before the
pollution entered the remaining natural portions of
the Everglades.¹³⁸

Although many drained peatlands are in intensive
and successful agricultural use, few areas would
justify the associated GHG emissions if those
emissions were properly valued. For example, one
study estimated the value of palm oil at $600 per
hectare per year on the most productive oil palm
plantations¹³⁹—and oil palm plantations on peat
are typically less productive than those on nonpeat
soils. But the value of avoiding the likely peatland
emissions alone would be $2,750 per hectare per
year at $50 per ton of CO₂e,¹⁴⁰ which is well below
typical estimates of the carbon costs the world will
need to pay to solve climate change.¹⁴¹ Because
oil palm plantations need to be replanted at high
cost roughly every 25 years, economically rational
opportunities could exist in some situations to
rewet peatlands in productive oil palm plantation
areas at the natural end of their productive life.

Probably the easier restoration opportunities,
politically and economically, are to be found in the
millions of hectares of drained peatlands that have
some kind of combination of shrub-like vegetation
or dispersed, small-scale agriculture. Although no
detailed compilation exists, peatland researchers
broadly agree that such lands exist.¹⁴² In the main
islands of Indonesia, 45 percent of peatlands con-
verted to agriculture as of 2015 were not in planta-
tions but displayed the kind of dispersed cropland,
shrubland, and cleared land that is characteristic of
smallholder farming. Although there is no detailed
analysis of the uses of such lands, the mapping used
to identify them indicates that the overall farming
intensity is relatively low (at least by comparison
with plantations), and people do not typically live
on these peatlands in large numbers. More drained
peatland is probably included in areas that satellite
images identify as shrublands or cleared lands.¹⁴³

One prominent peatland is a roughly 1 Mha area
in Central Kalimantan, Indonesia, that the govern-
ment attempted to convert to rice production via
the Mega Rice Project beginning in 1995. Due to
poor yields and fires, rice production either never
started or was abandoned. The area now exists
largely as a drained, cleared, and degrading site.

Established in 2008, the Indonesia-Australia
Forest Carbon Partnership attempted to restore
these peatlands, but it created a variety of local
controversies as different communities negotiated
the compensation or benefits they would receive for
agreeing to restoration. Amid widespread frustra-
tion with the lack of progress, Australia abandoned
the effort in 2014.¹⁴⁴

Fortunately, Indonesian President Joko Widodo
announced in 2016 a goal to restore 2 Mha of
peatland by 2020 (Box 21-1). This announcement
came after massive peatland fires in 2015 that,
in addition to releasing carbon, caused 500,000
people to be hospitalized. Although this effort is far
from fully funded, Indonesia allocated $35 million
to peatland restoration in 2017. By 2018, the Peat
Restoration Agency reported having rewetted more
than 100,000 ha of land, although the standard
used involves rewetting only up to 40 centimeters
below the surface, so some degradation of soils will
continue to occur.¹⁴⁵

Massive peatland fires in Russia in 2010 also led
to an effort with Wetlands International to rewet
abandoned peatlands, although its reach has so far
been very modest.¹⁴⁶

Restoring peatlands in Southeast Asia and else-
where also could generate ongoing economic
returns to offset some of the costs.¹⁴⁷ For example,
peatlands that naturally supported forests could
likely accumulate an amount of carbon from
reforestation at rates that could justify substantial
carbon payments. Although it would forgo many
biodiversity benefits, another option might involve
use of rewetted peatlands for agricultural or forest
products that could grow well under wet conditions.
Some valuable woods, such as European black
alder, grow naturally on peatlands. Some European
wetland grasses, such as reed canary grass, grow at
sufficient yields to contemplate their use for bio-
energy. (If produced as part of a strategy to restore
peatlands, wetland grasses would generate large
climate benefits, although more from the restora-
tion of peatland than from the provision of bio-
mass.) A German project demonstrated that reed
fibers could produce fire-resistant boards, while
cattail could produce excellent insulation materi-
als. Cultivation of sphagnum moss could produce a
valuable additive for horticulture.¹⁴⁸ Another study
found that native Indonesian peatland plants could
## BOX 21-1 | Indonesia's commitment to peatland restoration

The 2015 fire season was the worst in Indonesia's history, resulting in more than 500,000 people being treated for respiratory illnesses, and causing more than $16 billion in economic losses.ª Analysts estimate that 2.1 Mha of land and forest burned, resulting in 1.6 Gt CO₂e (more than Japan's annual total emissions) being released from fires that year.ᵇ The fires occurred largely on drained peatlands converted to oil palm and timber plantations.

To prevent another fire disaster of this scale, President Joko Widodo announced at the UN Framework Convention on Climate Change Conference of the Parties (COP) 21 in Paris the establishment of the Peat Restoration Agency (Badan Restorasi Gambut, or BRG), an agency mandated to restore 2 Mha of peatland by 2020.ᶜ The president established the BRG through Presidential Regulation No. 1/2016, which lays out a plan to coordinate and accelerate the recovery of Indonesia's critical peatlands.

The BRG's restoration efforts will prioritize seven provinces: Riau, Jambi, South Sumatra, Papua, and West, East, and Central Kalimantan. Out of Indonesia's estimated 12.9 Mha of peatland, 6.7 Mha are degraded and have potential for restoration, while 6.2 Mha are intact with potential for stronger protection. The BRG's first year focused on identifying and mapping the extent and depth of peat domes in four districts in Sumatra and Kalimantan, totaling an area of 644,000 ha. In 2017, the BRG began coordinating and implementing peatland restoration activities in the target districts. The agency is working to mobilize nongovernmental organizations, companies, civil society, and the development community to support its efforts.ᵈ

### Sources:

a. Lamb (2015).

b. Harris et al. (2015).

c. Jong (2015).

d. Wardhana (2016).

produce a wide range of valuable products, including a candlenut that the study found could even exceed the returns for oil palm.¹⁴⁹ Taking advantage of these opportunities may require a coordinated set of investments to support their establishment or marketing, and few have been tested in the real world. But the fact that some plants can grow well even in undrained peatlands suggests that at least some economic opportunities might exist to help support their restoration.

To estimate the potential benefits of peatland restoration, we estimate the GHG emission reductions that would result from restoring 25 percent, 50 percent, and 75 percent of all drained peatlands globally. (The higher number would require some peatlands currently used productively for agroforestry or forest plantations to be rewetted at the time they would otherwise need replanting.) Table 21-1 summarizes the potential GHG emissions benefits of these three scenarios, which would close the overall GHG emissions gap by between 2 and 7 percent.

### Recommended Strategies

Pursuing peatland conservation and restoration requires better data, resources, regulation, and political commitment.

#### Better peatlands data and mapping

As our discussion indicates, mapping of peatland extent is today based on rough estimates because peatlands often cannot be identified by satellite imagery. Mapping relies on national soil surveys, typically conducted for planning agricultural uses, which do not technically identify peatlands but rather identify soils that are characteristic of peatlands. But the quality and effort put into this type of soil mapping is uneven across the world, particularly in more remote areas. This information also does not convey the depth of peat, whether the peatland is presently cropped and drained, or the depth of the drainage. All this information is important to ensure conservation of existing undrained peatlands and identify the optimal restoration opportunities. An international entity or entities will need to step forward and supply the necessary resources and coordination for development of quality and detailed global maps of peatland extent, depth, drainage status, and use.

#### Resources

First and foremost, restoration requires resources both to fund the physical restoration and, usually, to compensate in some way existing users of the land for their forgone uses. Ideally, this compensation could take the form of assistance to help boost yields of crops outside of peatlands, replacing the forgone food production.
<table><caption>Table 21-1 | Potential of peatland restoration to reduce greenhouse gas emissions</caption><thead><tr><th>SCENARIO</th><th>ANNUAL GHG EMISSIONS FROM PEATLANDS (2010-50) (MT CO<sub>2</sub>E)</th><th>CHANGE IN SIZE OF GHG EMISSIONS GAP BETWEEN 2050 BASELINE AND 2050 TARGET</th></tr></thead><tbody><tr><td>Baseline</td><td>1,103</td><td></td></tr><tr><td>25 percent peatland restoration</td><td>827</td><td>-2%</td></tr><tr><td>50 percent peatland restoration</td><td>552</td><td>-5%</td></tr><tr><td>75 percent peatland restoration</td><td>276</td><td>-7%</td></tr></tbody></table>

Sources: WRI analysis based on Yu et al. (2010); You et al. (2014); Hiraishi et al. (2014); Biancalani and Avagyan (2014); and van der Werf et al. (2017).

To date, peatland restoration projects have demonstrated technical potential but have been carried out at small scales and in limited contexts. Yet they probably offer one of the least expensive carbon savings of any land-use option, particularly where drained peatlands are now little used. International financial entities aiming to support climate change mitigation, including the Green Climate Fund, the World Bank, and national development assistance agencies, should work together to develop a major global funding initiative on peatland restoration.

## Regulation

There is little reason for governments of peat-rich countries or the world's wealthier nations to pay to restore peatlands in one location if farmers can easily shift food production and drain peatlands elsewhere. Governments should therefore establish, and enforce, strong laws protecting peatlands from further drainage or conversion. Indonesia, for example, issued a regulation in 2016 placing a moratorium on clearing peatland until a zoning system for the protection of peatlands and cultivation in peatlands is in place. The moratorium also specified that degraded areas must be restored, although implementation is still at an early stage.¹⁵⁰

Governments should also consider laws that will not leave the continued use of drained peatlands as assured, regardless of their economic benefits. Although many of those who now benefit from drained peatlands have compelling social arguments for some form of compensation for restoration—preferably as other economic opportunities—emissions from peatlands should not be immune

from government regulation any more than other sources of emissions.

## Political commitment

Even when drained peatlands are little used, experience indicates that someone is nearly always using them in ways that take advantage of the drainage. Even in the largely abandoned Mega Rice Project area of Indonesia, local people engage in some modest agriculture, and they have used the canals as a means of transportation (for boats or timber), which is easier than trying to move directly through typically saturated peat.¹⁵¹ Because peatland drainage typically requires networks of drainage ditches, restoration usually proceeds in a series of blocks (e.g., by blocking drainage ditches), affecting multiple people and sometimes multiple communities, and it is hard to get all to agree. Australia's efforts to restore the peatlands of the Mega Rice Project faltered in large part because some groups of people objected to the compensation deals as they unfolded, and occasional negative press emerged based on these objections.

Restoring peatlands, like most other infrastructure projects, has high potential to arouse opposition from some parties, even if the benefits to the public are clear and the project has the support of the vast majority of those directly affected. Efforts to move forward must be sensitive to issues of equity and seek participation and consent but should respect majority support. Projects will not succeed without a strong political commitment to see projects through.
ENDNOTES

1. FAO (2019a).

2. FAO (2019a).

3. Alexandratos and Bruinsma (2012), Table 4.8.

4. GlobAgri-WRR model.

5. To appreciate shifts in locations of agricultural land, an analysis must evaluate how small, specific areas of land change over time, and not simply calculate how the total agricultural land within a country changes over time. The shifts only became possible to analyze once satellites could track locations of all land-use changes over time.

6. Reprinted from Figure 11 of FAO (2012e).

7. Lindquist et al. (2012).

8. Aide et al. (2012) for Latin America; Lark et al. (2015) for U.S.

9. Kuemmerle et al. (2016).

10. Millennium Ecosystem Assessment (2005); Grenyer et al. (2006); Searchinger, Estes, Thornton et al. (2015); Sitch et al. (2015); Wheeler et al. (2016).

11. Aide et al. (2012); Lark et al. (2015).

12. Gibson et al. (2011).

13. West et al. (2010).

14. Hirsch et al. (2004).

15. Aide et al. (2012). The shift in grazing land from dry land in Australia to Latin America is also a good example of this type of shift.

16. Alexandratos and Bruinsma (2012).

17. GlobAgri-WRR model.

18. Van Ittersum et al. (2016).

19. Van Ittersum et al. (2016).

20. Searchinger, Estes, Thornton et al. (2015).

21. FAO (2019a).

22. Bruinsma (2009) predicts an increase in soybean production from 218 Mt in 2006 to 514 Mt in 2050, with a rise in yield from 2.3 t/ha to 3.7 t/ha during that period, leading to an increase in harvested area to 141 Mha. Masuda and Goldsmith (2009) only look out to 2030 and project a "business as usual" scenario in 2030 where 371 Mt of soybeans will be produced on 141 Mha of land.

23. In Latin America, Brazil and Argentina are two of the three largest soybean producers in the world. Africa's potential to produce soybeans is described alternatively in Gasparri et al. (2016) and Searchinger, Estes, Thornton et al. (2015).

24. Soyatech (n.d.).

25. Oil World (2015).

26. UNCTAD (2015).

27. UNCTAD (2015).

28. Pacheco (2012); Greenpeace (2012); Rainforest Foundation UK (2013).

29. For example, see Rainforest Foundation Norway (2012).

30. Corley (2009). Corley's estimate is for palm oil for edible purposes and "traditional" nonedible purposes (which do not include biofuels). Rushing and Lee (2013) project up to an additional 15 Mha of palm oil plantation expansion globally from 2010 or 2012 level (the base year is unclear in the publication) to 2050. The implications of current (2015) low prices for palm oil remain to be seen. For instance, it could delay the timing of expansion until prices rise again. One should note that some oil palm clones are capable of yielding 11 metric tons per hectare (which is way above the current average 4-5 metric tons per hectare), so there is still an upside potential in palm oil yields (D. McLaughlin, personal communication, April 30, 2015). However, getting selected clones to become mainstream is not a foregone conclusion.

31. Laurance et al. (2014); Laurance et al. (2009); Edwards et al. (2014); Busch and Ferretti-Gallon (2017); Seymour and Busch (2016); Vera-Diaz et al. (2009); Fearnside (1982); Chomitz and Gray (1996).

32. Seymour and Busch (2016).

33. Laurance et al. (2009); Laurance et al. (2006). See also summary of articles in Searchinger, Estes, Thornton et al. (2015).

34. Ahmed et al. (2014); Blake et al. (2007).

35. Laporte et al. (2007).

36. Laurance et al. (2014).

37. Ali et al. (2015); Delgado et al. (1998); African Agricultural Development Company (2013); Gollin and Rogerson (2010).

38. Jouanjean (2013).

39. Vera-Diaz et al. (2009).

40. Laurance et al. (2014).

41. Laurance et al. (2015).
42. Laurance et al. (2015).

43. AIIB (2016).

44. Angelsen and Kaimowitz (2001); Ewer et al. (2009); Rudel (2009).

45. Searchinger (2012); Villoria et al. (2014); Hertel et al. (2014).

46. Dorward (2012).

47. If yield increases occur because of increases in other inputs, including chemicals, machinery, or labor, then these nonland costs are likely to increase. This issue is often confused in the literature because studies tend to model effects on land not from increases in yield alone but rather from increases in total factor productivity, which assumes increases in productivity of all inputs and therefore declines in costs of producing crops and, in turn, prices. See, for example, Hertel et al. (2014).

48. Stevenson et al. (2013).

49. Searchinger, Edwards, Mulligan et al. (2015); HLPE (2011); Dorward (2012); Filipski and Covarrubia (2010).

50. Gallett (2010).

51. Hertel et al. (2014).

52. The same yield growth may not precisely influence costs of production in the same way in each country, so this statement is only true roughly and in general.

53. Estimates of these rates of conversion of grasslands to croplands vary but are all in millions of hectares. Lark et al. (2015); WWF (2016).

54. Hoering (2013).

55. Van Ittersum et al. (2016); FAO (2002).

56. Butler (2013).

57. Rosenbarger et al. (2013).

58. Mulyani and Jepson (2013).

59. Recio (2015).

60. Jackson (2015); Nepstad et al. (2014); Assunção et al. (2012); Gibbs et al. (2016).

61. Do Carmo (2017).

62. Wormington (2016).

63. Cameron (2015).

64. Fagan et al. (2013).

65. Murdiyarso et al. (2011); Austin et al. (2012).

66. Palmer (2015).

67. Busch and Ferretti-Gallon (2017). See also Porter-Bolland et al. (2012).

68. Seymour and Busch (2016).

69. Busch and Ferretti-Gallon (2017).

70. Blackman et al. (2017).

71. Busch and Ferretti-Gallon (2017).

72. This paragraph is based on Seymour and Busch (2016); see esp. Chap. 7 for a fuller discussion of how to stop tropical deforestation. See also Colchester et al. (2006).

73. See www.globalforestwatch.org.

74. Seymour and Busch (2016).

75. See, for example, Frank et al. (2017). We do not necessarily endorse the specific findings of this paper, but it does provide one estimate of the likelihood that stopping land-use changes without sufficient, exogenous yield gains will result in an increase in food prices and food insecurity.

76. Data for the following paragraph come from Assunção et al. (2013).

77. Assunção et al. (2013).

78. Annual deforestation rates in Brazilian Amazon with data from INPE (Brazilian National Institute of Space Research) are summarized by Butler (2017).

79. The Brazil story is summarized in Jackson (2015).

80. Jackson (2015).

81. Laurance et al. (2014).

82. Estes, Searchinger, Spiegel, et al. (2016).

83. Climate Focus (2016); Donofrio et al. (2017).

84. Consumer Goods Forum (2014).

85. University of Cambridge, Institute for Sustainability Leadership (2019).

86. University of Cambridge, Institute for Sustainability Leadership (2019). The founding member banks are Barclays, Deutsche Bank, Lloyds Banking Group, Santander, Westpac, BNP Paribas, RBS, and UBS.

87. Fabiani et al. (2010).

88. Gibbs et al. (2015).

89. Gibbs et al. (2015).
90. Soy production in Brazil in 1991 was about 20 million metric tons. In 2005, it was about 56 million metric tons. In 2007, it was about 61 million metric tons. In 2011 and 2013, it was about 75 million metric tons and 82 million metric tons, respectively. Data for 1991 through 2009 are from the U.S. Department of Agriculture, as reported in Boucher et al. (2011). Data for 2011 and 2013 are from USDA (2019).

91. Taylor and Streck (2018).

92. Nepstad et al. (2014).

93. Boyd et al. (2018).

94. Papers using this term in the bioenergy context include Gelfand et al. (2013); Nijsen et al. (2012); and Wicke et al. (2011).

95. Cai et al. (2011).

96. Borras et al. (2011); Baka and Bailis (2014).

97. Federici et al. (2015); Pan et al. (2011); Richter and Houghton (2011).

98. For example, in Palm et al. (2013), an important and oft-cited book focusing on tropical land conversion, the approach recommended focuses on calculations of costs per hectare, not per ton of crop.

99. Nijbroek and Andelman (2016).

100. Estes, Searchinger, Spiegel, et al. (2016).

101. Koh and Ghazoul (2010).

102. Imperata grasslands store less than 20 tons of carbon per hectare (tC/ha), compared to more than 100 tC/ha in secondary forests and more than 200 tC/ha in the primary forests of Sumatra and Kalimantan, Indonesia. Figures include both biomass and necromass (Fairhurst et al. 2010).

103. Chapin et al. (2000).

104. Fairhurst and McLaughlin (2009).

105. This figure reflects the area classified as "grassland" by Sarvision's radar-based satellite imagery of Kalimantan in 2010. Unpublished analysis conducted by WRI.

106. Garrity et al. (1997).

107. One study estimates a need for 3 to 7 million hectares of additional oil palm plantations in Indonesia between 2010 and 2020; for links and citations of these figures, see Gingold (2010).

108. Maginnis et al. (2005).

109. See, for example, Stern (2006); Nabuurs et al. (2007); Sathaye et al. (2011); and Sathaye et al. (2005).

110. Griscom et al. (2017).

111. Buckingham and Hanson (2015b).

112. Hua et al. (2016).

113. Siddique et al. (2008).

114. Jactel et al. (2017).

115. Hua et al. (2016). For example, bee diversity in plantations was 5% of that of croplands overall except for eucalyptus.

116. Hua et al. (2016).

117. These estimates of beef production come from Cardoso et al. (2016), which discusses the level of beef production per hectare on pastureland under different forms of management in the Cerrado. Although the Atlantic Forest is a separate region, we estimate that the beef production on sloped pasture in this region is similar to that of the lowest management in the Cerrado, based on personal communications with the authors.

118. See http://www.bonnchallenge.org/commitments.

119. Hanson et al. (2015).

120. Searchinger et al. (2018).

121. Searchinger et al. (2018).

122. Buckingham and Hanson (2015b).

123. Global soil maps tend to map not peat but "organic soils," which are soils with 12% or more soil organic matter. Our mapping of peatlands globally uses organic soils designations.

124. Kolka et al. (2016).

125. Kolka et al. (2016).

126. Morrogh-Bernard et al. (2003); Posa et al. (2011); Sunarto et al. (2012).

127. Mietinnen et al. (2016).

128. For all of Indonesia, and using its own definition, Indonesia's Ministry of Environment and Forestry as of 2017 estimates 24.14 Mha of peatland hydrological units on National Zoning of Peatland Ecosystems.

129. Mietinnen et al. (2016).

130. See full description of methodology for estimating both land areas on peatlands and emissions in note 139.

131. Biancalani and Avagyan (2014).

132. IPCC (2014).
133. Our analysis used the global map of peatland regions from Yu et al. (2010) to calculate the area of cropland on peat soils, the SPAM maps of crop distribution (You et al. 2014), emission factors recommended by the IPCC in a special report on wetlands (Hiraishi et al. 2014), except that we used a single emission factor of 55 tCO₂/ha/yr for both oil palm and acacia plantations based on work by scientists with Wetlands International for reasons described in Biancalani and Avagyan (2014). We also estimated annual average peatland fire emissions based on the Global Fire Emissions Database version 4 (van der Werf et al. 2017).

134. Gumbricht et al. (2017); Joosten et al. (2012).

135. Dargie et al. (2017).

136. Joosten et al. (2012); Biancalani and Avagyan (2014); Rochefort and Andersen (2017); Bonn et al. (2016).

137. Biancalani and Avagyan (2014), Box 7.

138. Grunwald (2018).

139. Abram et al. (2016).

140. This calculation is based on the emission rate of 15 tons of carbon per hectare per year for oil palm in peat based on the emission factors discussed in Biancalani and Avagyan (2014).

141. Cost estimates vary greatly, but $50 is still below the mean, undiscounted estimated mitigation cost in 2030 to hold warming to 2 degrees Celsius based on analysis by the IPCC. See Rogelj et al. (2018), Figure 2.26(a).

142. Joosten et al. (2012).

143. Mietinnen et al. (2016).

144. Davies (2015).

145. Gewin (2018).

146. Wetlands International (n.d.).

147. The examples in this paragraph are all summarized by FAO in Biancalani and Avagyan (2014).

148. Biancalani and Avagyan (2014).

149. Biancalani and Avagyan (2014).

150. See ANTARA News (2016) and Pickup (2017) for more details on Indonesia's Government Regulation no. 57/2016.

151. Nugraha and Jong (2017).

## REFERENCES

To find the References list, see page 500, or download here: www.SustainableFoodFuture.org.

## PHOTO CREDITS

Pg. 234 Mokhamad Edliadi/CIFOR, pg. 237 Kate Evans/CIFOR, pg. 238 Icaro Cooke Vieira/CIFOR, pg. 246 Kate Evans/CIFOR, pg. 255 Patrick Shepherd/CIFOR, pg. 258 PXhere.com, pg. 264 Ollivier Girard/CIFOR, pg. 272 Nanang Sujana/CIFOR.
<figure><img src="image_140.png" /></figure>
## COURSE 4

# Increase Fish Supply

The global wild fish catch reached a peak in the mid-1990s but it has since stagnated and may even have declined. Roughly one-third of marine fish stocks are now overfished, with another 60 percent fished at maximum sustainable levels. This course explores ways to improve wild fisheries management and raise the productivity and environmental performance of aquaculture to meet rising demand for fish.

## TABLE OF CONTENTS

* Chapter 22. Menu Item: Improve Wild Fisheries Management 287

* Chapter 23. Menu Item: Improve Productivity and Environmental Performance of Aquaculture 293
<figure><img src="image_141.png" /></figure>
MENU ITEM:
IMPROVE WILD
FISHERIES
MANAGEMENT

Fish are an important source of protein, especially for people in developing countries. Yet the annual amount of fish caught in the wild—particularly from the oceans—has stagnated and may have significantly declined since the 1990s. Continued overfishing threatens future catch levels and improved management will be essential to allow fish stocks to rebound.
## The Challenge

Fish, including finfish and shellfish,¹ are a minor source of the global calorie supply, but they contributed 17 percent of global animal-based protein for human consumption in 2010 (Figure 6-4).² Fish are particularly important in developing countries, which consume more than 75 percent, and produce more than 80 percent, of global fish supply.³ Fish also contain important micronutrients—such as vitamin A, iron, and zinc—and long-chain omega-3 fatty acids that are essential for maternal health and early childhood development but are often deficient in the diets of the poor.⁴

According to the Food and Agriculture Organization of the United Nations (FAO),⁵ the world produced 171 million tons (Mt) of fish in 2016. Wild fisheries produced 91 Mt, which provided 71 Mt of fish for people and 20 Mt for animal feed and other nonfood uses.⁶ The global fisheries catch has grown almost fivefold since 1950. Yet since the 1990s, the catch has at best stagnated. FAO data show such a stagnation with a slight increasing trend in inland fish landings offsetting a slight decline in marine fish landings (Figure 22-1).⁷ Research by Pauly and

Zeller (2016) is even more pessimistic, concluding that FAO's numbers underestimate both total marine fish catches and the rate of decline since the 1990s. Using an approach called “catch reconstruction,” Pauly and Zeller estimate that the global marine fish catch peaked at 130 Mt in 1996 (nearly 50 percent higher than FAO's estimate for that year) and since then has declined at an average rate of 1.2 Mt per year, with serious implications for the future marine catch.⁸

The percentage of marine fish stocks that are overfished is also near an all-time high. By 2015, 33 percent of marine fish stocks were overfished, with another 60 percent fished at maximum sustainable levels, and only 7 percent fished at less than their full potential (Figure 22-2).⁹

The tropics present particular challenges. Fish catches are greatest in the tropics—particularly in Southeast Asia.¹⁰ Climate change is also likely to have substantial future effects by reducing productivity and fish size, disturbing fish habitats, and changing species composition as fish move toward cooler waters.¹¹

<figure><img src="image_142.png" /><figcaption>Figure 22-1 | The wild fish catch has stagnated (or possibly declined) since the 1990s</figcaption></figure>

Note: "Wild catch" includes finfish, mollusks, crustaceans, and other aquatic animals from marine and freshwater ecosystems. It excludes all aquaculture. It does not include catch reconstruction as in Pauly and Zeller (2016).

Source: FAO (2019b).
## The Opportunity

Reducing overfishing, which would prevent future declines and allow depleted stocks to recover, is the first important step toward a sustainable fish supply. The World Bank suggests that world fishing effort¹² needs to decline by 5 percent per year over a 10-year period, which would allow fisheries to rebuild to an ideal level over three decades.¹³ Although this approach would likely reduce catches in the short term, it should lead to productive and sustainable wild fish catches over the long term—possibly 10 Mt above 2012 levels.¹⁴ Another study has estimated that economically optimal global fisheries management could even lead to a sustainable annual fish catch 18 Mt above 2012 levels by 2050.¹⁵

Some recent experience supports this claim. Although fisheries in developed countries have also been overfished, fish stocks appear to be rebounding along the coasts of a few developed countries such as Australia, New Zealand, Norway, and the United States.¹⁶

The United States has made significant progress in reducing overfishing in recent decades. The Magnuson-Stevens Fishery Conservation and Management

Act, signed in 1976 and strengthened through subsequent amendments, created a mandate to rebuild overfished stocks. Since 2000, 44 fish stocks have been rebuilt and, as of 2017, just 15 percent of U.S. stocks were overfished—the lowest percentage since assessments began.¹⁷ Overall U.S. fish catch, which peaked around 6 Mt in the late 1980s and dropped to just over 4 Mt in 2009, seems to be stabilizing around 5 Mt.¹⁸ Success has come about through a variety of measures, notably through strict enforcement of annual catch limits—including use of catch share programs—and monitoring of fish stock health.

In Kenya, a comanagement program between the Fisheries Department and traditional fisheries leaders led to a rebound of coastal coral reef fish populations and increased the profitability of fishing. Two management strategies—gear restriction (a ban on small-meshed beach seine nets, implemented between 2001 and 2004), and closing off areas of the sea from fishing (implemented between 2005 and 2009)—were responsible for these results. In areas where these management strategies were in place, catches per fisher per day rose by approximately 50 percent between 2000 and 2012, and fisher incomes

<figure><img src="image_143.png" /><figcaption>Figure 22-2 | The percentage of overfished stocks has risen over the past 40 years</figcaption></figure>

Source: FAO (2018).
doubled during this period, all while maintaining overall catch levels. At landing sites near the Mombasa Marine National Park, a no-fishing area, the sizes of fish caught were higher (fetching higher prices). Catches also contained species of higher market value relative to the catches in areas farther from no-fishing areas.¹⁹ These positive changes occurred even in the wake of the 1997–98 El Niño event that caused widespread loss of coral cover in the fishing grounds, suggesting that (at least during the study period) the improved fisheries management practices were able to counter the effects of disturbances from climate change.²⁰

We project fish consumption to rise 58 percent between 2010 and 2050,²¹ but the wild fish catch peaked at 94 Mt in the mid-1990s and has since stagnated or perhaps declined. For our 2050 baseline scenario, we assume a 10 percent decrease in global wild fish catch between 2010 and 2050 (an annual catch in 2050 that is 9 Mt below 2010 levels). This baseline assumes a continuation of business as usual, with some stocks rebuilding and others continuing to decline due to overfishing.²² We also use GlobAgri-WRR to model an improvement scenario where wild fish catch—instead of declining between 2010 and 2050—stays constant at 2010 levels, a scenario where many, but not all, stocks have measures in place to stop overfishing and rebuild. The effect in GlobAgri-WRR of being able to harvest an additional 9 Mt of wild fish (relative to 2050 baseline) is to avoid the need for

an additional 9 Mt of farmed fish, which reduces aquaculture's total land demand in 2050 by 5 million hectares (Mha), and closes the emissions gap by 0.6 percent (Table 22-1).²³

## Recommended Strategies

Strategies to curb overfishing and maintain harvests at sustainable levels are well documented in other studies.²⁴ They focus on several key principles:

- Limiting fish catch (including bycatch) to a level that allows the population to reproduce

- Limiting the number of fishers to an economically sustainable level

- Protecting habitat

- Avoiding harvest during important breeding times or in important breeding areas²⁵

Tools to implement these strategies include establishing total allowable catches based on optimum sustainable yield, gear restrictions, seasonal limits, regulation or direct government management of key habitats, and closure of breeding areas.

Widespread implementation of these strategies is difficult for various reasons—listed below—most of which are political and socioeconomic and based on the fact that wild fish are a public resource that individual fishers have incentives to exploit before others can do so:²⁶

<table><caption>Table 22-1 | Global effects of 2050 fisheries improvement scenario on the food gap, land use, and the GHG mitigation gap</caption><thead><tr><th rowspan="2">SCENARIO</th><th rowspan="2">FOOD GAP, 2010-50 (%)</th><th rowspan="2">GHG MITIGATION GAP (GT CO<sub>2</sub>E)</th><th colspan="3">AQUACULTURE LAND USE (MILLION HA)</th></tr><tr><th>Ponds</th><th>Cropland for feed</th><th>Total</th></tr></thead><tbody><tr><td>2010</td><td>N/A</td><td>N/A</td><td>19</td><td>27</td><td>46</td></tr><tr><td><strong>2050 BASELINE</strong></td><td><strong>56.5</strong></td><td><strong>11.1</strong></td><td><strong>40</strong></td><td><strong>52</strong></td><td><strong>92</strong></td></tr><tr><td>Stable wild fish catches between 2010 and 2050 (Coordinated Effort, Highly Ambitious, Breakthrough Technologies)</td><td>56.3</td><td>11.0</td><td>38</td><td>49</td><td>87</td></tr></tbody></table>

Source: GlobAgri-WRR model.
* Rebuilding a fishery or halting overfishing typically involves a decline in fishing activity and landings for some period of time. Consequently, fishers and others in the value chain can experience financial losses over the near to medium term. There is no compelling short-term economic reward for acting sustainably.

* There are economic winners and losers in efforts to rebuild stocks, and the potential losers often wield enough power to thwart reform and fishery restoration efforts.

* Many countries subsidize fishing in a variety of ways that lead to overfishing.²⁷ Recent studies estimate global annual fisheries subsidies at $35 billion—equivalent to one-third of the value of global fisheries production.²⁸ In total, the World Bank estimated that annual lost revenues from mismanagement of global fisheries was $83 billion in 2012.²⁹

* Because of global power imbalances, foreign fleets from richer countries often are able to obtain “fishery access agreements” to fish in the waters of poorer countries with weaker laws and enforcement capacity.³⁰

* Illegal, unregulated, and unreported fishing is a widespread problem, particularly in developing countries. Worldwide, losses from illegal fishing and unreported fishing have been estimated at $10 billion and $23.5 billion per year, respectively, representing an additional catch of between 11 Mt and 26 Mt that goes unmanaged.³¹

* Lack of data and lack of infrastructure and resources for monitoring and enforcement can be a barrier to active management.

* Fishing is often a livelihood of last resort in many poor coastal communities, and small-scale fishing continues to grow across the developing world. In addition, fishing has played an important cultural role in coastal areas for centuries. In the absence of alternative livelihoods, governments can be hesitant to curtail local fishing operations out of social concerns, even in depleted coastal waters.

In recent years, some developed countries have been able to overcome these challenges by limiting the number of fishers and using “catch shares.”

These systems establish shares of fish that may be taken and allocate them among individual fishers. These fishers therefore acquire a long-term stake in the health of the fishery, and can often trade their shares.

In the United States, progress in rebuilding fisheries has resulted in part from shifting to systems of “catch shares” that reduce the “race to fish.”³² Based on evidence from 39 commercial fisheries, researchers have credited these programs with making catch levels more predictable and stable, reducing the number of fishing boats, improving fishing crew safety, reducing bycatch, and promoting other favorable environmental and economic outcomes.³³ However, because catch share programs can facilitate industry consolidation and the marginalization of small-scale fishers,³⁴ governments will need to address the social consequences of this consolidation.

In developing countries where oversight, rule of law, and monitoring arrangements are weaker, additional approaches are needed. In these governance environments—as the Kenya example illustrates—community-based comanagement systems may prove more effective. Such systems combine territorial fishing rights and no-take reserves designed and supported by coastal fishing communities.³⁵

All told, overcoming the barriers listed above requires a set of complementary strategies, adapted to suit specific circumstances.³⁶ For example, establishing resource rights and removingverse subsidies can control access to fish resources at economically and biologically feasible levels. Adoption of sustainable procurement practices and certification systems by actors in fish supply chains could help create demand for sustainably sourced fish. Both these rights and markets strategies, in turn, could build support for governance reforms regarding fishing practices and marine spatial management. However, for these strategies to succeed, enabling conditions such as sound data and science, supply chain transparency, and law enforcement need to be in place.³⁷ Advocacy, public pressure, technical and financial support, and outreach to major players in fish supply chains can all help put these enabling conditions in place and advance these strategies.
<figure><img src="image_144.png" /></figure>
# MENU ITEM: IMPROVE PRODUCTIVITY AND ENVIRONMENTAL PERFORMANCE OF AQUACULTURE

Despite stagnating or declining wild fish catches, world fish consumption has continued to increase as aquaculture has grown to meet global demand. This menu item involves increasing production of farmed fish relative to the amount of land, freshwater, feed, and energy used—while minimizing water pollution, fish diseases, and escapes.
## The Challenge

The aquaculture (fish farming)³⁸ sector is diverse. Fish farming produces more than 300 species and occurs in nearly every country in the world.³⁹ Aquaculture is practiced in three different environments: In 2016, 63 percent of production was in freshwater (mostly in ponds on land), 28 percent in marine waters, and 9 percent in brackish water (coastal ponds).⁴⁰

Between 2011 and 2016, aquaculture production rose in every world region.⁴¹ In 2016, aquaculture provided more than half of all fish people consumed—80 Mt—making it one of the world's fastest-growing animal food-producing sectors.⁴² Asia accounted for nearly 90 percent of global aquaculture production in 2016, and China alone accounted for more than 60 percent (Figure 23-1). In terms of percentage increase, sub-Saharan Africa had the fastest rate of growth—increasing production by nearly 50 percent between 2011 and 2016—but because its baseline was low, the region contributed less than 1 percent of global aquaculture production in 2016.

Because the wild fisheries catch peaked years ago, virtually all of the future increase in world fish consumption will need to come from aquaculture. If global per capita fish availability is to meet projected demand under our 2050 baseline scenario, where wild fish supply declines by 10 percent, we estimate that aquaculture production would need to more than double between 2010 and 2050, rising from 60 Mt in 2010 to roughly 140 Mt in 2050 (Figure 23-2). Meeting this demand presents environmental, production, and social challenges.⁴³

### Land-use change

In 2010, global aquaculture occupied an estimated 19 Mha of land—an area the size of Syria—including 13 Mha of inland (freshwater) areas and 6 Mha of coastal (brackish water) ponds. Aquaculture also indirectly used an additional 27 Mha that year—an area larger than the United Kingdom—to grow plant-based feeds.⁴⁴ In total, aquaculture occupied about 1 percent of global agricultural land,⁴⁵ and conversion of agricultural lands or natural ecosystems to aquaculture contributes to the overall competition for land.

<figure><img src="image_145.png" /><figcaption>Figure 23-1 | Nearly 90 percent of aquaculture production is in Asia</figcaption></figure>

Note: Data may not sum to 100% due to rounding.

Source: FAO (2019b).
Aquaculture's impact on mangroves raises particular concerns. Mangroves are among the most productive ecosystems in the world, serving as nursery grounds for many fish and protecting coastlines. In the 1980s and 1990s, a largely unregulated boom in shrimp aquaculture led to clearing of significant areas of mangroves for aquaculture ponds.⁴⁶ Conversion of mangroves to aquaculture has slowed since 2000, thanks to improvements in shrimp-farming practices and mangrove protection policies.⁴⁷ Between 2000 and 2012, however, the world lost 192,000 hectares of mangroves, about 1 percent of total global mangrove cover,⁴⁸ with more than 100,000 hectares being lost in Southeast Asia alone. Richards and Freiss (2016) estimate that 30 percent of the mangrove losses in Southeast Asia in this period were due to aquaculture expansion (followed by clearing for rice [22 percent] and oil palm [16 percent]). Indonesia, in particular, witnessed major aquaculture expansion: of 60,000 hectares of mangroves lost, half were cleared for aquaculture.⁴⁹ It remains an ongoing challenge in some areas to reconcile plans for increasing aquaculture production with mangrove protection.⁵⁰

## Greenhouse gas emissions

In 2010, we estimate that aquaculture production was responsible for greenhouse gas (GHG) emissions of 332 million tons of carbon dioxide equivalent (Mt CO₂e)—less than 1 percent of total human emissions but 5 percent of emissions from agricultural production.⁵¹ Aquaculture's emissions arise from on-farm energy use; feed production; transportation, processing, and packaging of produce; and disposal of wastes. Aquaculture's largest energy demands tend to occur during production of fish and feeds.⁵² Untreated pond sediments can lead to methane emissions.⁵³ A further source of emissions is the conversion of land and coastal habitats for aquaculture development, both directly through conversion of carbon-rich ecosystems (such as mangroves, seagrass beds, and wetlands) and indirectly by displacing croplands.

<figure><img src="image_146.png" /><figcaption>**Figure 23-2 | Aquaculture production must continue to grow to meet world fish demand**</figcaption></figure>

Source: Historical data 1950–2016: FAO (2019b) and FAO (2018). Projections to 2050: calculated at WRI; assume 10% reduction in wild fish catch from 2010 levels by 2050, linear growth of aquaculture production of 2 Mt per year between 2010 and 2050.
## Additional environmental challenges

Aquaculture can trigger other environmental challenges, as well. First, the use of wild fish as feed ingredients can exacerbate pressure on marine ecosystems. The small, oily fish commonly harvested for aquaculture feed—such as anchovy—are near the bottom of the marine food chain. In 2016, 15 Mt of wild fish (or nearly one-fifth of the marine catch) was converted to fishmeal and fish oil, most of which was consumed by aquaculture.⁵⁴

Another challenge is water pollution. Discharges can contain excess nutrients from fish feed and waste, antibiotic drugs, other chemicals (e.g., pesticides, hormones, antifoulants), and inorganic fertilizers. In comparison to terrestrial livestock production, it is difficult to collect wastes from aquaculture production because they are rapidly dispersed into the surrounding water.⁵⁵ Pollution associated with aquaculture can cause degradation of aquatic habitats and eutrophication of lakes or coastal zones, and can even directly threaten the aquaculture operation itself.⁵⁶

A third challenge is infectious disease, which has devastated shrimp production in parts of Asia. Early Mortality Syndrome (first noted in 2009) presents ongoing threats to the shrimp sector. Parasites, such as sea lice, have caused problems for salmon production, for example in Chile and Norway.⁵⁷ Diseases and parasites can also be transferred from farmed to wild fish (and vice versa) in open production systems.⁵⁸

Another concern is that farm-raised fish can escape, or be intentionally released, from aquaculture facilities and cause genetic contamination. Escaped fish can breed with, outcompete, or prey on native fish, altering ecosystem structure and composition.⁵⁹

Finally, food safety worries exist, too. These include the excessive use of antimicrobial products at fish farms, which can spread antimicrobial resistance in human pathogens (e.g., *Salmonella*). Another is the potential for farmed fish to contain high levels of chemical contaminants, such as persistent organic pollutants, pesticides, and heavy metals, which could be harmful to consumers.⁶⁰

## Social concerns associated with aquaculture

**Human nutrition.** Farmed fish are generally as lean and protein-rich as chicken,⁶¹ but one concern of aquaculture is that farmed fish as a whole tend to have lower levels of long-chain omega-3 fatty acids than wild fish.⁶² Nutrient composition of fish depends on a number of factors including the species, whether the fish is wild or farmed, and the feeding methods.⁶³ If fish are to continue to meet this valuable nutritional need, they will require an enhanced, alternative supply of complex oils.

**Availability and affordability of fish for human consumption.** The use of wild fish for aquaculture feed is a complicated issue. On the one hand, it may reduce the amount of wild fish available for direct human consumption while it produces relatively large fish targeted at middle-class markets.⁶⁴ As the vast majority of the small fish harvested for feed is of food-grade quality, aquaculture could reduce fish access for the poor. On the other hand, there is limited market demand for direct consumption of these small fish.⁶⁵ Aquaculture can also benefit the poor if its output becomes cheap enough. For example, in Egypt and Bangladesh, strong recent growth of aquaculture production has pushed the prices of farmed fish below those of wild fish, making fish more broadly accessible to the poor.⁶⁶

## Input constraints and climate change

Land-use limitations are a key constraint on aquaculture growth. In Asia, for instance, little land is available for aquaculture (or any agricultural) expansion.⁶⁷ An important challenge will be for aquaculture to more than double production between 2010 and 2050 while minimizing land expansion.⁶⁸

In 2010, aquaculture consumed an estimated 201 cubic kilometers (km³) of freshwater, accounting for approximately 2 percent of global agricultural water consumption.⁶⁹ Freshwater inland aquaculture uses water to maintain pond levels, compensating for water lost through seepage, evaporation, and intentional discharge. More intensive systems use frequent water exchanges to aerate and filter ponds.
Production of plant-based fish feeds also consumes water.⁷⁰ However, freshwater is becoming increasingly scarce in many aquaculture-producing areas because of upstream dams and diversion of water for agriculture and urban uses.⁷¹

Feed could be another constraint. In 2016, at least 70 percent of aquaculture production used some form of feed, whether fresh feeds (e.g., crop wastes), feed mixed and processed on the farm, or commercially manufactured feed.⁷² Carnivorous species⁷³—such as salmon, shrimp, and many other marine finfish—tend to rely on wild-caught fish (in the form of fish meal and fish oil in commercially manufactured feeds) to receive adequate protein and lipids in their diets.⁷⁴ Conversely, roughly 80 percent of aquaculture production in 2014 consisted of omnivores, herbivores, and filter feeders that consume little to no fish-based ingredients.⁷⁵ Commercial feeds for omnivores and herbivores tend to contain cereals, oilseeds, and pulses, often in the form of meals and oils.⁷⁶ The fact that the supply of fish meal and fish oil from wild sources is already near its historical highs and ecological limits represents a clear constraint on aquaculture production growth, particularly of farmed carnivorous fish.⁷⁷ However, it will also be a challenge to ensure an adequate supply of plant-based proteins, oils, and carbohydrates for aquaculture feed as the sector grows, while minimizing the associated land and water-use impacts.⁷⁸

Land, water, and feed are all likely to be adversely affected by climate change.⁷⁹ Farms in deltas and coastal and marine areas are most immediately exposed to flooding, sea level rise, and extreme weather events. Increases in water temperature will likely increase the occurrence of harmful algal blooms, which reduce water quality and can render farmed fish unfit for human consumption.⁸⁰ Ocean acidification also threatens the long-term viability of shellfish aquaculture.⁸¹ At the same time, climate change may also open up new production opportunities in certain areas and make aquaculture an adaptation strategy. In colder regions, warmer temperatures may enable aquaculture, and in coastal land areas that become too saline for agriculture, aquaculture could become an important adaptation strategy (Chapter 15).⁸²

## The Opportunity

If annual aquaculture production were to increase from 60 Mt in 2010 to 140 Mt by 2050, as projected in our baseline food demand scenario, significant food security and development benefits could result. For example, this level of growth would boost annual fish protein supply to 19 Mt, or 6 Mt above 2010 levels.⁸³ Such an increase would meet 13 percent of the increase in global animal protein supply between 2010 and 2050 under our baseline scenario.⁸⁴ It would boost income and employment, particularly in developing countries, where most aquaculture growth will occur.⁸⁵ And the global value of farmed fish could increase from $120 billion in 2010 to $308 billion in 2050, with the number of people engaged in aquaculture for a living increasing from 100 million in 2010 to 176 million by midcentury.⁸⁶

Even though aquaculture poses environmental challenges, it has potential advantages relative to most other animal-based foods. Because finfish live in an environment that supports their body weight, are cold-blooded, and excrete waste nitrogen directly as ammonia, they devote less energy to metabolism and bone structure than terrestrial animals.⁸⁷ As a result, most farmed species convert feed into edible meat quite efficiently. As discussed in Chapter 6 on shifting diets, farmed finfish are similar in feed conversion efficiency to poultry, and much more efficient than beef and sheep (Figure 6-5).⁸⁸ Filter-feeding carp and mollusks are even more efficient producers of animal protein, as they require no human-managed feeds and can improve water quality by removing excess microalgae and nutrient pollution from lakes and coastal waters.⁸⁹ Furthermore, expansion of marine aquaculture could help alleviate the land constraint relative to other animal-based foods and their associated emissions from land-use change.
Per ton of edible protein, aquaculture species require between 0 ha (mollusks) and 16 ha (shrimp) of land per year, which is less than pork and chicken (both around 20 ha per year) and far less than beef (140 ha per year) (Figure 6-6).⁹⁰ Aquaculture also produces lower GHG emissions than ruminant meats. Per ton of edible protein, farmed fish production emits around 30 tons of CO₂e per year, which is similar to emissions from pork and chicken production, and again far less than emissions from beef production (more than 200 tons of CO₂e per year). Another consideration is that, because the aquaculture sector is relatively young compared with terrestrial livestock sectors, there is great scope for technical innovation to further increase its resource efficiency.

Opportunities to sustainably intensify aquaculture production (Box 23-1), to reduce its environmental impacts, and to overcome basic production constraints exist in at least five interrelated areas:⁹¹

## BOX 23-1 | Classifying aquaculture production systems by intensity

The aquaculture literature commonly classifies production systems by their level of intensity. Intensity of production runs along a spectrum from *extensive* (less than 1 ton of fish per hectare per year [t/ha/yr]) through *semi-intensive* (2–20 t/ha/yr) and *intensive* (20–200 t/ha/yr) farms.ª Yields from intensive cage, raceway, or recirculating systems can be higher still.ᵇ In general, according to Hall et al. (2007), levels of intensity can be summarized as follows:

*   Extensive production requires a low level of control, relies on natural productivity and crop wastes as feed, and has relatively low operating costs.

*   Semi-intensive production uses fertilizers and farm-made feed to boost fish yields, which requires a higher level of management control and involves higher operating costs.

*   Intensive production requires the highest degree of management control, relies completely on off-farm inputs (e.g., high-quality feed, seed, and fertilizers), and uses more energy, leading to high operating costs.

**Sources:**

a. Bunting (2013).

b. Dugan et al. (2007).

## Breeding and genetics

To overcome land-use constraints, aquaculture needs to improve growth rates and conversion efficiencies. Fish bred for faster growth rates⁹² could lead to more efficient use of land and sea area, water, feed, and labor.⁹³ Fortunately, there are large opportunities to breed more efficient fish, as aquaculture lags far behind crop and livestock agriculture in the use of selective breeding; in 2010, less than 10 percent of world aquaculture production was based on genetically improved stocks.⁹⁴ Because feed often accounts for 50 percent or more of all production costs, these efficiencies should also improve the economics of production.⁹⁵

Of the approximately 100 large-scale aquaculture breeding programs in the world in 2010, more than half were focused on just three species: Atlantic salmon, rainbow trout, and Nile tilapia. Less than 10 percent focused on carp, which is by far the most abundant aquaculture species group.⁹⁶ Selective breeding efforts could be expanded, aimed at countries and species with the highest levels of production (e.g., Chinese carps), and at areas of current low productivity yet high need for aquaculture growth (e.g., sub-Saharan Africa). Selective breeding also could reduce disease problems, enable increased use of plant-based ingredients in feed, and lead to the eventual development of truly domesticated fish that do not survive or breed in the wild, lessening problems of escapes.

## Fish oil alternatives and other feed improvements

Aquaculture continues to rely heavily on wild fish-derived fish meal and fish oil. However, since both are finite resources, the aquaculture industry cannot continue this reliance as it continues rapid growth into the future. The supply of fish meal and fish oil from wild sources is already at historical highs and is near ecological limits, which represents a clear constraint to aquaculture growth.⁹⁷ To continue its growth, the aquaculture industry will therefore need an alternative source of the key nutrients found in fish oil—omega-3 eicosa-pentaenoic acid (EPA), and docosahexaenoic acid (DHA) (Box 23-2). Both EPA and DHA omega-3 are required for optimal fish health and growth and are also important essential fatty acids for human nutrition.
Microalgae (the origin of omega-3 fatty acids in fish oil) can provide a viable substitute for wild fish-based ingredients and use much less land and water than is required for plant-based oil crops.⁹⁸ Another possible plant-based substitute for fish oil is genetically engineered yeasts or oilseed plants (e.g., rapeseed) that produce omega-3 fatty acids.⁹⁹ However, further investments in research and development will be necessary to bring costs of these replacement ingredients below fish oil prices. Continued research is also necessary to further improve understanding of optimal omega-3 fatty acid nutritional efficiency of all important aquaculture species, while also minimizing waste and production costs.

## Disease control

Disease outbreaks continue to constrain aquaculture production, especially in more intensive systems. New technologies will be essential to lessen risks from disease and reduce the need for antibiotics.¹⁰⁰ Promising technologies include advanced diagnostics, vaccines, dietary supplements, and genetic improvements. Also helpful will be wider application of best management practices, such as reducing water exchange in ponds or tanks, reducing water seepage in ponds, improving feed and feeding practices, improving sanitation, and not stocking fish too densely in ponds or cages.

## Water recirculation and other pollution control

Recirculating water used in aquaculture can save water and allow the producer greater control over water temperature, oxygen levels, and other aspects of water quality. As a result, conditions improve for the farmed fish, allowing for better growth, lower disease levels, more predictable harvests, and higher levels of intensity. However, recirculation also adds to operating costs and energy use (and production-related GHG emissions).¹⁰¹ Water recirculation is not the only option for pollution control; other improved management practices, such as using settling ponds before releasing wastewater, can also reduce waste.

## BOX 23-2 | Microalgae are a promising alternative to fish oil in aquaculture feeds

Fish and the fish-derived product, fish oil, currently represent the main dietary source of long-chain omega-3 fatty acids for human nutrition. Omega-3 fatty acids generally refer to three fats, namely alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Of these, EPA and DHA are the long-chain omega-3s, which are naturally present in fish, marine algae, krill, and human milk. They are associated with key human health benefits. Daily intake of at least 250 mg of EPA and DHA has been shown to benefit eye, brain, and heart health.ª However, there are currently no large-scale alternatives to fish oil that are rich in both EPA and DHA omega-3 fatty acids, meaning that fully replacing fish oil in aquaculture feed with other animal or plant-based oils would reduce the level of EPA and DHA omega-3 and therefore the nutritional benefit of farmed fish to the consumer.ᵇ

The omega-3 fatty acids EPA and DHA are naturally produced by algae in the natural marine food chain and gradually accumulated in larger fish. These larger fish are harvested for fish oil production, and fish oil therefore contains EPA and DHA omega-3 fatty acids. Fish oil alternatives are essentially based on utilizing the ability of microalgae to produce omega-3 fatty acids, either by direct production of microalgae or by transferring their biochemical capability (e.g., genes) to other organisms such as yeast or oilseed plants through genetic engineering. Although it remains to be seen which technologies ultimately prove to be economically viable, and socially acceptable, at large scale, it appears that several fish oil alternatives will be available on the market within the next few years.

One example of a promising fish oil alternative is an algal strain of *Schizochytrium sp.* that naturally produces both EPA and DHA omega-3 through fermentation. Using sugar as an energy source, the algae cells grow, multiply, and convert sugar into the omega-3 fatty acids EPA and DHA. A refining process then produces an algal oil rich in both EPA and DHA that can substitute for fish oil—as well as a by-product that can be used for animal feed or bioenergy. Evonik and DSM have founded a joint venture, Veramaris®, to commercialize this technology, which they say will be on the market in 2019 and initially able to meet 15 percent of the salmon aquaculture industry's demand for EPA and DHA.ᶜ

**Sources:**

a. Zhang et al. (2018).

b. Sprague et al. (2016).

c. Van der Hoeven (2018); Veramaris (2018).
## Expansion of marine-based systems

Offshore marine aquaculture, which would avoid additional land-use change as well as problems of competition for space in coastal areas by locating farms in the open sea, is still in its infancy.¹⁰² One recent study found that the global physical potential for expanding marine aquaculture is vast—that marine aquaculture could fully supply farmed fish demand by 2050 even if only 1 percent of the suitable area in each coastal country were developed. However, the study did not assess important economic or biodiversity-related constraints to expansion of marine-based systems, suggesting that the true growth potential was still significant, but lower than the pure physical potential.¹⁰³

To better understand the efficacy of various strategies to meet these challenges while boosting aquaculture production to 140 Mt by 2050, we use GlobAgri-WRR to build on lifecycle assessments performed by WorldFish and Kasetsart University. These assessments are reported in more detail in Mungkung et al. (2014) and Waite et al. (2014).¹⁰⁴ The analysis divides world aquaculture into 75 major production systems, which accounted for more than 80 percent of total world aquaculture production in 2010. We integrated this analysis into the GlobAgri-WRR model and used the model

to explore a 2050 baseline and three additional aquaculture production scenarios with the following characteristics:

* **Baseline.** Aquaculture production rises to 140 Mt in 2050. Proportions of fish species cultivated and production systems used (e.g., composition of feeds, intensity level of production) remain unchanged between 2010 and 2050. But increasing resource scarcity leads to market conditions that cause farmers to improve their production efficiency so that they produce each kg of fish with 10 percent less use of all major inputs (e.g., water, feed, energy, fertilizers).

* **Doubling efficiency gains** (Coordinated Effort scenario). Between 2010 and 2050, farmers improve production efficiency by 20 percent instead of 10 percent thanks to further improvements in fish breeding, feeds, and disease and pollution control.

* **Accelerated intensification on land** (Highly Ambitious scenario). Freshwater pond farming—the current dominant production system around the world—becomes significantly more intensive as farmers invest in the technologies described in the preceding

<table><caption>Table 23-1 | Global effects of 2050 aquaculture improvement scenarios on the food gap, land use, and the GHG mitigation gap</caption><thead><tr><th rowspan="2">SCENARIO</th><th rowspan="2">FOOD GAP, 2010-50 (%)</th><th rowspan="2">GHG MITIGATION GAP (GT CO<sub>2</sub>E)</th><th colspan="3">AQUACULTURAL LAND USE (MILLION HA)</th></tr><tr><th>Ponds</th><th>Cropland for feed</th><th>Total</th></tr></thead><tbody><tr><td>2010</td><td>N/A</td><td>N/A</td><td>19</td><td>27</td><td>46</td></tr><tr><td><strong>2050 BASELINE</strong></td><td><strong>56.5</strong></td><td><strong>11.1</strong></td><td><strong>40</strong></td><td><strong>52</strong></td><td><strong>92</strong></td></tr><tr><td>Doubling efficiency gains (from 10% to 20% between 2010 and 2050) (Coordinated Effort)</td><td>56.3</td><td>11.0</td><td>36</td><td>49</td><td>85</td></tr><tr><td>Accelerated intensification on land (Highly Ambitious)</td><td>57.0</td><td>11.1</td><td>27</td><td>60</td><td>87</td></tr><tr><td>Doubling efficiency gains plus accelerated intensification on land (Breakthrough Technologies)</td><td>56.7</td><td>11.0</td><td>24</td><td>56</td><td>80</td></tr></tbody></table>

Source: GlobAgri-WRR model.
section. Fifty percent of all farms classified as "extensive" (Box 23-1) in 2010 shift to "semi-intensive" by 2050, and 50 percent of "semi-intensive" farms in 2010 shift to "intensive" by 2050.

* Doubling efficiency gains plus accelerated intensification on land (Breakthrough Technologies scenario). This scenario is a combination of the two previous scenarios.

Table 23-1 shows the results from these scenarios. Under the 2050 baseline scenario, land under aquaculture ponds doubles between 2010 and 2050 and cropland for aquaculture feeds also doubles because there is no additional potential to provide more feed from wild fish.

Doubling the increase in production efficiency from 10 percent (under baseline) to 20 percent reduces total land demand by 7 Mha relative to the baseline scenario, closing the food gap by 0.4 percent and the GHG emissions gap by 0.8 percent.

The scenario of accelerated intensification on land leads to a trade-off among two types of land use. The switch to more intensive production systems by 2050 leads to a savings in 13 Mha of land under aquaculture ponds relative to baseline. However, since more intensive production systems tend to require more feeds—and we required all additional feeds to be crop-based rather than wild-fish-based—the land savings from the reduced pond area are offset by an 8 Mha increase in cropland used to produce aquaculture feeds. This surprising result suggests that extensive ponds are essentially functioning both as homes for the fish and as producers of algae for feed. GlobAgri-WRR also estimated that overall emissions (even with the reduced land overall relative to baseline) would actually *increase* by 19 Mt per year, due to the higher energy use in intensive ponds.

The third scenario, which combines the doubled efficiency with the accelerated intensification on land, eases the trade-offs from the intensification-only scenario. Under this third scenario, cropland use rises by only 4 Mha relative to baseline (instead of 8 Mha in the intensification-only scenario), while

the use of land for ponds falls by 16 Mha relative to baseline (instead of 13 Mha in the intensification-only scenario). Overall, emissions would decrease by 66 Mt per year relative to baseline, as the avoided land-use change offsets the higher energy use in intensive ponds.

Overall, we favor shifts toward more intensive ponds in part because land “saved” overall from pond expansion is likely to be more carbon-rich than the additional land required for feed crop expansion. This is because ponds must generally use wet, flatter lands. In addition, potential exists to reduce the land-use demands for feed either by further increasing crop yields or by further accelerating efficiency gains (e.g., breeding fish to convert feed to flesh more efficiently or to grow faster and therefore increase output per hectare of pond). Connecting intensive ponds to renewable sources of energy could reduce production emissions from intensive aquaculture.

<figure><img src="image_147.png" /></figure>
This analysis, and the broader life cycle assessment done by Mungkung et al. (2014) that examined additional aquaculture growth scenarios and other environmental factors, including water use and pollution, illustrate a real challenge. Under a projected doubling in global aquaculture production between 2010 and 2050, it will be hard enough to hold aquaculture's environmental impacts to 2010 levels, let alone reduce them. Mungkung et al. (2014) also showed that intensification, while reducing aquaculture's freshwater demand, would lead to a rise in water pollution unless accompanied by further technological advances. A deeper analysis of the trade-offs under scenarios of aquaculture growth, with more detailed data, is needed to provide insights at finer scales (e.g., national level). For example, Phillips et al. (2015) analyzed scenarios of Indonesian aquaculture growth to the year 2030. Their analysis underscored the challenges of meeting projected fish demand while safeguarding high-conservation-value ecosystems such as mangroves and wetlands, limiting freshwater use, and finding alternatives to wild-fish-based feed ingredients.

## Recommended Strategies

If aquaculture is to more than double production, sustainably, between 2010 and 2050, the sector must increase its natural resource efficiency and reduce other environmental impacts, including fish diseases and escapes. Several strategies are necessary to realize this potential.

### Increase investment in technological innovation and transfer

Technological advances by scientists, researchers, and innovative farmers—and widespread uptake of improved technologies—will be necessary to address the various land and feed constraints and to fully exploit the opportunities for aquaculture to grow efficiently and with minimal environmental impacts, as demonstrated by the salmon farming industry in Norway (Box 23-3). These advances could also help aquaculture adapt to a changing climate.¹⁰⁵ While numerous initiatives are directed at technological innovation and transfer, their present scale is insufficient to achieve the necessary change by 2050. Because most aquaculture occurs in

<figure><img src="image_148.png" /></figure>
developing countries, where production growth in coming decades is expected to be highest, initiatives should focus on helping small- and medium-scale producers in developing countries access and adopt improved technologies.¹⁰⁶ In India, for example, small-scale shrimp farmers organized into “societies” that enabled them to access new technologies, services, and markets that otherwise might have been limited to large-scale farmers.¹⁰⁷

National governments, development agencies, the aquaculture industry, international organizations, nongovernmental organizations (NGOs), private foundations, and farmers all have a role to play. Because public budgetary resources are limited, innovative financing arrangements with the private sector, such as private equity investment, will be needed.¹⁰⁸

## Use spatial planning to optimize aquaculture siting

Much of aquaculture growth to this point has been “organic” or “opportunistic” and led by a dynamic private sector.¹⁰⁹ Resource and economic constraints, the potential for increased conflicts between resource users, and the need to boost production significantly in a short time mean that the locations of future aquaculture systems must be chosen more strategically.

Spatial planning and zoning include processes and tools such as land-use planning, water-use planning, ecosystem modeling, marine spatial planning, integrated coastal zone management, and integrated watershed management. These approaches can lessen the conflicts between a growing aquaculture industry and other economic actors competing for the same resources, such as land, especially if done in a participatory way. Planning focused at the landscape and seascape level can also reduce cumulative impacts caused by many farmers operating in the same area and help minimize risks associated with climate change. In Norway, for example, zoning laws ensure that salmon producers are not overly concentrated in one area, reducing disease risk and helping mitigate environmental impacts.

## BOX 23-3 | Sustainability gains in Norway's salmon farming industry

Norway, the world leader in salmon (*Salmo salar*) production, has made dramatic sustainability gains over the past 30 years. The share of fishmeal and fish oil in salmon diets has been reduced by about two-thirds between 1990 and 2013, antibiotic use virtually eliminated, and fish escapes reduced from nearly 1 million in 2006 to roughly 143,000 in 2018.ª Meanwhile, salmon production has grown from about 150,000 tons in 1990 to 1.2 million tons in 2016.ᵇ

Technological improvements, stimulated by high levels of public and private investment in research and development, have been at the core of these improvements in productivity and environmental performance. Development of vaccines and disease control methods has greatly reduced the need for antibiotics.ᶜ Selective breeding and improved feeds have both led to greater production efficiency and reduced the reliance on wild fish for feed.ᵈ Industry consolidation and vertical integration has enabled companies to invest heavily in research and development, increasing production efficiency and driving down production costs. And public policies—including permitting, spatial planning and monitoring systems, as well as establishing protected areas for wild salmon—have helped stimulate and support these improvements.ᵉ

In the last few years, salmon farming has encountered an enhanced problem from sea lice, a parasite that thrives in confined salmon pens, kills or makes unmarketable large numbers of fish, and spreads to wild salmon, possibly reducing their numbers greatly. The lice problem has become sufficiently large that farmed salmon production fell between 2015–16, both in Norway and globally.¹ Overall, parasites and disease present some of the biggest threats to continued aquaculture expansion.

**Sources:**

a. Ytrestøy et al. (2015); Taranger et al. (2014); WHO (2015); Directorate of Fisheries (2019).

b. FAO (2019b).

c. WHO (2015).

d. Ytrestøy et al. (2015).

e. Torgersen et al. (2010).

f. Castle (2017).
<figure><img src="image_149.png" /></figure>

Spatial planning and zoning can also prevent aqua-culture development in high-conservation-value areas, such as mangroves (as in Thailand) or wild salmon areas (as in Norway), and protect upstream areas essential to maintaining coastal water quality (as in the United States).

More national and subnational governments need to establish legal frameworks for spatial planning and zoning for aquaculture, create aquaculture development plans that link to wider development plans, and invest in monitoring and enforcement to ensure plan implementation. A number of initiatives are already in place that promote participation in aquaculture planning and take landscape- and seascape-level concerns into account,¹¹⁰ but additional effort is necessary.

## Introduce policies to reward sustainable intensification

Complementary policies, namely regulations, standards, taxes, subsidies, and market-based mechanisms, can encourage sustainable intensification. For example, in Thailand, the government has provided shrimp farmers operating legally

in aquaculture zones with access to free training, water supply, and wastewater treatment. The Thai government has also provided low-interest loans and tax exemptions to small-scale farmers, helping them adopt improved technology that increased productivity, reducing pressure to clear new land.¹¹¹ Similar policies have helped stimulate the growth and intensification of the catfish industry in Vietnam (Box 23-4). And in Denmark, stringent wastewater standards have encouraged investment in recirculating aquaculture systems.¹¹²

## Establish aquaculture monitoring systems

Advances in satellite technology, digital mapping, ecological modeling, open data, and connectivity mean that global-level aquaculture monitoring and planning systems may now be possible. A global-scale platform that integrates these technologies and builds on existing information-sharing efforts could help companies, governments, and civil society encourage and support sustainability in the aquaculture sector. Such a platform could combine national- or global-level map layers (e.g., on farm locations, land use and type, water quality, weather), georeferenced data (e.g., on fish
production and value, fish trade, environmental performance), and bottom-up crowdsourcing of information (e.g., photos or stories to report successes, best practices, or areas of concern). Many different users could benefit from information technologies:

- Fish buyers could ensure that their purchases are from responsible suppliers, and producers and suppliers could use objective data to demonstrate that their operations are sustainable.

- Producers could access market information, as well as early warnings about water quality issues, disease outbreaks, and risks associated with natural disasters.

- Producers could communicate success stories, access technical guidance, and network with other producers and technical assistance agencies to improve operations.

- Governments could use data on current facility locations and environmental and social factors to improve spatial planning, detect illegally sited operations, and target monitoring and law enforcement efforts.

- NGOs and communities could report stories of improvements in productivity and social and environmental performance that could inspire actors in other areas. Conversely, they could monitor aquaculture operations in their area and raise an alarm if laws are being broken or resources are threatened.

A globally applicable monitoring and planning system could also help concerned citizens everywhere learn more about this dynamic, rapidly growing food production sector, helping to ease often polarized debates around aquaculture and build coalitions in favor of sustainable aquaculture growth.

For more detail about this menu item, see
"Improving Productivity and Environmental
Performance of Aquaculture," a working paper
supporting this World Resources Report available
at www.SustainableFoodFuture.org.

BOX 23-4 | Technology and government support drive intensification of catfish farming in Vietnam

In Vietnam's upper Mekong Delta region, striped catfish (*Pangasius hypophthalmus*) production grew 20-fold between 2000 and 2010, while catfish farming areas only roughly doubled, indicating a very rapid period of intensification. Catfish exports brought in $1.4 billion in foreign exchange in 2010.ª This rapid production increase has led to the development of other sectors along the value chain, including hatchery production, fillet processing, and feed production. The catfish boom during the first decade of the 21st century created nearly 180,000 new jobs in the Mekong Delta, the majority of which are performed by rural women in the processing sector.ᵇ A recent life cycle analysis noted that pollution from catfish ponds was equal to or less than that of other food production sectors in the Mekong Delta, and that water quality had not degraded to a point where it threatened the viability of aquaculture production or compromised other downstream water uses.ᶜ

Technological improvements—including a breakthrough in artificial propagation of striped catfish in hatcheries around the year 2000, adoption of higher-quality pelleted feed, and improvements in pond farming techniques—combined to trigger the boom in catfish production. Supportive government policies, including research and extension programs, subsidized bank loans for producers and processors, and trade liberalization and promotion, have also helped to grow and support this export-oriented industry, and allow it to provide an affordable “white fish” substitute in Europe and the United States.ᵈ

Going forward, the biggest short-term risk to the industry's sustainability is the continued economic viability of farm operations if production costs (e.g., feed) rise. Protectionism in importing countries also poses a threat; wild fishing and aquaculture sectors in the United States and Europe have lobbied during the past 15 years to restrict imports of Vietnamese catfish.ᵉ In addition, the Vietnamese catfish industry will also need to secure sustainable supplies of feed and water, while continuing to limit disease outbreaks.*f

Sources:

a. De Silva and Phuong (2011).

b. De Silva and Phuong (2011).

c. Bosma et al. (2009).

d. Phuong and Oanh (2010).

e. Little et al. (2012).

f. Phuong and Oanh (2010).
ENDNOTES

1. Throughout this report, "fish" refers to both finfish and shellfish. More precise definitions of these terms, and others used throughout this report, include *finfish*—a cold-blooded animal that lives in water, breathes with gills, and has fins and scales; *shellfish*—refers to both crustaceans and mollusks; *crustacean*—an animal belonging to the phylum Arthropoda that (usually) lives in water, has several pairs of legs, a body made up of sections, and is covered in a hard outer shell; *shrimp*—a decapod crustacean of the suborder Natantia; and *mollusk*—an animal belonging to the phylum Mollusca that has a soft unsegmented body without a backbone and usually lives in a shell (FAO 2008).

2. Authors' calculations from FAO (2019a). In 2015, fish provided roughly 3.2 billion people with 20% of their animal protein intake (FAO 2018).

3. Authors' calculations from FAO (2019a). In 2013, 77% of the human food supply of fish was located outside of North America, Europe, Oceania, and other OECD countries, suggesting a similar percentage of world fish consumption in developing countries.

4. Allison (2011).

5. Many figures in this report are based on statistics from the FAO Fish-Stat global database of wild fisheries and aquaculture production (FAO 2019b) and the FAO's *State of World Fisheries and Aquaculture* (FAO 2018). However, the FAO fisheries and aquaculture production data rely on reports of member countries, and the quality of the data varies by country and may be subject to reporting bias. Many member countries have been found to misreport fisheries landings, catch levels may be underreported as discussed in note 9, and collection of aquaculture data remains relatively new. See Kura et al. (2004) (Annex B); Campbell and Pauly (2013); CEA (2012); and Pauly and Zeller (2016) for further discussion of FAO fisheries and aquaculture data, limitations, and caveats.

6. FAO (2018).

7. FAO (2019b). While the FAO capture fisheries data show a decline in marine fish catch since the 1990s, the data also show that the inland fish catch is still slightly rising. As with marine fisheries, inland fisheries are important to human protein consumption, especially for the poor. However, the slight increase in inland fish catch in the FAO data is probably a result of better reporting of actual catches rather than an increase in the amount of fish landed, and many believe that inland fisheries are in decline as well because of overfishing and aquatic ecosystem degradation (Welcomme 2011).

8. Pauly and Zeller (2016) cited underestimates in the FAO FishStat data around small-scale (both commercial and subsistence) fisheries, recreational fisheries, discarded bycatch, and illegal or otherwise unreported catch—and estimated the extent of these missing components to "reconstruct" true levels of marine fish catches.

9. FAO (2018). Data are from periodic FAO fish stock assessments. According to FAO (2018), *overfished* stocks produce lower yields than their biological and ecological potential, *maximally sustainably fished* stocks produce catches that are very near their maximum sustainable production, and *underfished* stocks are under relatively low fishing pressure and have some potential to increase their production.

10. Watson and Tidd (2018).

11. Cheung et al. (2010, 2013).

12. As defined by the World Bank (2017d), fishing effort is a composite indicator of "the size and efficiency of the global fleet, usually measured in terms of the number of vessels, vessel tonnage, engine power, vessel length, gear, fishing methods, and technical efficiency."

13. World Bank (2017d).

14. World Bank (2017d).

15. Costello et al. (2016).

16. Examples summarized in CEA (2012); and Worm et al. (2009).

17. NOAA (2018).

18. FAO (2019b).

19. McClanahan and Abunge (2014); McClanahan (2010); McClanahan et al. (2008).

20. McClanahan and Abunge (2014).

21. Authors' calculations, assuming a 12% increase in per capita consumption between 2010 and 2050 due to growth in income and urbanization. This projection corresponds well to recent trends; fish demand and supply would match if wild fish supply were to fall by 10% between 2010 and 2050 and aquaculture supply were to continue to expand at its recent rate of ~2 Mt per year during that period.

22. This 10% decline to 2050 is also in line with the "business as usual" fisheries management scenario in Costello et al. (2016) (Table S15).

23. GlobAgri-WRR model.

24. See, for example, Worm et al. (2009); CEA (2012); Melnychuk et al. (2016); and World Bank (2017d).

25. CEA (2012).

26. The following observations about these six factors are based on and more thoroughly examined in CEA (2012).

27. World Bank (2017d).

28. Sumaila et al. (2010, 2012, 2016).

29. World Bank (2017d).
30. Worm et al. (2009).

31. Agnew et al. (2009). Some recent estimates of fish catch underreporting are even higher; Pauly and Zeller (2016) estimated that true marine fish catches could be 53% higher than those reported in FAO (2019b).

32. Birkenbach et al. (2017).

33. Grimm et al. (2012); Essington (2010); Brinson and Thunberg (2013); Birkenbach et al. (2017).

34. Spalding (2013); Costello et al. (2008). Although individual transferable quota (ITQ) programs have reduced fishing effort and improved the economic efficiency of the fishing industry, these programs also have disadvantages (the following examples are summarized in Kura et al. 2004). As with other forms of catch limits, it can be difficult to determine the optimal sustainable yield level of a given fishery, leading to continued overexploitation. ITQs can give fishers incentive to discard smaller or lower-priced fish back into the sea to avoid counting these fish against the quota, again leading to continued overexploitation. There are also social and equity issues associated with ITQs. ITQs reduce the number of fishers and vessels in a fishery, leading to increased unemployment and vulnerability in fishing-dependent communities in the short term. ITQs often encourage consolidation within a fishery, and as quota prices increase these programs may become monopolized by larger, better-funded fishing companies at the expense of more vulnerable small-scale fishers. The design of ITQ programs, like the overall regulation of fisheries, must be sensitive to the socioeconomic factors facing fisher communities, which vary considerably among countries.

35. CEA (2012).

36. The following observations are based on and more thoroughly examined in CEA (2012).

37. Melnychuk et al. (2016).

38. Aquaculture is commonly defined as the farming of aquatic organisms, which include both animals and plants (FAO 2008). Because the focus of this report is on aquaculture's potential to contribute to fish supplies, all data on aquaculture production omit production of aquatic plants (seaweeds). For the rest of the report, *aquaculture* is used to mean "the farming of aquatic animals."

39. FAO (2019b).

40. FAO (2019b).

41. This paragraph contains authors' calculations from FAO (2019b).

42. FAO (2018). Aquaculture is the fastest-growing animal production sector when measured by annual percentage rate of growth. By absolute annual amount of growth, aquaculture, poultry, and pork production have all grown at roughly 2-2.5 Mt per year since 1990, although aquaculture's growth since 2010 has been even faster at roughly 3.5 Mt per year.

43. The discussion below, unless otherwise cited, is from Tacon et al. (2010); Kura et al. (2004); Costa-Pierce et al. (2012); and Bunting (2013). Note also that aquaculture can have sometimes positive ecosystem effects; for example, providing seed for restocking of overexploited fish populations, or by providing wastes that can be used to fertilize terrestrial crops (Soto et al. 2008, 16).

44. Authors' calculations from GlobAgri-WRR model and Mungkung et al. (2014) (unpublished data). Assumes the following: all bivalves and coastal cage/pen aquaculture (e.g., of salmonids) occupied marine area and thus no land; everything classified as "coastal ponds" occupied brackish water area; everything else occupied freshwater area.

45. Authors' calculations. According to the GlobAgri-WRR model, total agricultural land was 4,785 Mha in 2010.

46. Lewis et al. (2002).

47. Lebel et al. (2016).

48. Strong and Minnemeyer (2015).

49. Richards and Freiss (2016).

50. See Phillips et al. (2015) for an example from Indonesia.

51. Mungkung et al. (2014). Figures do not include emissions from land-use change associated with aquaculture or agriculture.

52. Hall et al. (2011b).

53. Bunting and Pretty (2007).

54. FAO (2018).

55. Bouwman et al. (2013).

56. Kura et al. (2004).

57. Castle (2017); Bravo (2003).

58. Cooke (2018). Looking beyond issues of disease, some groups have raised concerns about the welfare of farmed fish—especially those raised in intensive systems. These groups make the case that fish are sentient beings and self-aware organisms, capable of feeling pain and stress. Intensive aquaculture systems raise concern about the well-being of fish as they undergo and experience stressful situations and conditions. These concerns are similar to animal welfare concerns related to intensive livestock farming, including overcrowding, feeding and handling, transport, and stunning and slaughter methods.

59. Lorenzen et al. (2012).

60. Hine et al. (2012).

61. USDA (2013a).

62. Beveridge and Brummett (2013).
63. Beveridge and Brummett (2013).

64. Cai et al. (2012).

65. Cashion et al. (2017).

66. Beveridge and Brummett (2013); Belton et al. (2012); Hernandez et al. (2017).

67. FAO (2007).

68. Croplands that have become too saline for rice cultivation are an example of such lands with low economic and environmental value.

69. Authors' calculations. Aquaculture water consumption given in Mungkung et al. (2014), global agricultural water consumption of 8,363 km³ per year (not counting aquaculture) given in Mekonnen and Hoekstra (2012).

70. Beveridge and Brummett (2013).

71. Costa-Pierce et al. (2012).

72. FAO (2018). As a low-bound estimate, "fed aquaculture production" consisted of at least 56 Mt of fish (out of 80 Mt of total aquaculture production in 2014, excluding seaweeds). This estimate excludes filter-feeding fish species (silver carp and bighead carp), freshwater fish production not reported down to the species level, and bivalve mollusks. Because even filter-feeding carp can be fed formulated feeds, the true amount of "fed aquaculture production" is likely higher than 70% of all production (Tacon et al. 2011).

73. Although the terms *carnivore*, *omnivore*, and *herbivore* are commonly used when describing the feeding habits of a fish species, it is more scientifically and etymologically correct to use the trophic level, which is an indication of how high a species sits in the aquatic food chain. For example, the "carnivorous" Atlantic salmon has a trophic level of 4.43, while the "herbivorous" common carp has a trophic level of 2.96 (Tacon et al. 2010). Farmed fish species have varying digestive and metabolic capacities to deal with different feed resources; for example, a high-trophic level "carnivore" requires a relatively high level of protein in its feed (Tacon et al. 2010). However, distinctions between "carnivores" and other groups can be misleading in aquaculture, because fish diets can be altered. For example, although the average salmon diet in 2008 contained 25% fishmeal and 14% fish oil (Tacon et al. 2011), it is technically possible to feed an Atlantic salmon using no fish-based ingredients at all. Still, in this section, we follow common usage to use the term *carnivores* to refer to salmonids, shrimp, and most marine finfish, and *omnivores/herbivores* to refer to other fed fish species.

74. Tacon et al. (2011).

75. Authors' calculations from FAO (2019b).

76. Tacon et al. (2011).

77. Naylor et al. (2009).

78. Tacon et al. (2011).

79. De Silva and Soto (2009).

80. De Silva and Soto (2009).

81. Watson et al. (2012).

82. De Silva and Soto (2009).

83. Authors' calculations based on an assumption of the same ratio of fish protein weight to total fish weight in 2050 as in 2010 (implying the same mix of fish species).

84. Authors' calculations.

85. See Hall et al. (2011b) for a discussion predicting the geographic distribution of aquaculture growth to 2030.

86. Authors' calculations:

*Global value of farmed fish.* Here, we assume that between 2010 and 2050, real prices of fish rise on average by 10%. The World Bank, FAO, and IFPRI (2013) project that real prices of all farmed fish will rise between 2010 and 2030, by 5 to 10% depending on the species. We therefore believe that a global real price increase of 10% by 2050 is reasonable.

*Livelihoods from aquaculture.* Here, we assume that between 2010 and 2050, average family sizes will remain constant, and that aquaculture labor productivity will continue to grow at its 2000–10 historical rate. FAO data show that between 2000 and 2010, world aquaculture production grew by 82%, while aquaculture employment grew by only 47% (FAO 2014a, 2014b). A similar trajectory between 2010 and 2050—where the aquaculture employment growth rate is only 57% of the aquaculture production growth rate—would lead to the industry providing livelihoods for 176 million people by 2050.

87. Costa-Pierce et al. (2012).

88. Costa-Pierce et al. (2012). However, while the feed efficiency figures in Figure 7-4 count grass consumed by terrestrial animals, they do not count plankton and other organic (nonfeed) matter consumed by fish, as data on volume of aquatic organic matter consumed by fish are sparse. Fry et al. (2018) come to a similar conclusion on the relative conversion efficiency of aquaculture and terrestrial livestock, while also noting that farmed fish and shrimp require higher levels of protein and calories in feed compared to chickens, pigs, and cattle.

89. Hall et al. (2011b). However, in order to provide food that is safe for consumers, filter-feeders must be raised in high-quality waters. And although coastal waters tend to have more than abundant nutrients, there are often many competing uses of these areas (analogous to competition for agricultural land), limiting scope for expansion of aquaculture.

90. GlobAgri-WRR model; Waite et al. (2014).

91. Volpe et al. (2010); Asche (2008).

92. This section focuses on "conventional" selective breeding (as opposed to genetic modification).
93. Gjedrem et al. (2012).

94. Gjedrem et al. (2012). Nearly all Atlantic salmon production is based on genetically improved stock, but the rates of use of improved stock for production of other species is much lower.

95. Garnett and Wilkes (2014).

96. Gjedrem et al. (2012).

97. Naylor et al. (2009).

98. Smith et al. (2010); Taelman et al. (2013). Table 4 in Taelman et al. (2013), which displays the results of a lifecycle assessment comparing algae-based feeds to conventional aquaculture feed, shows that algae-based feeds reduced land use demands by 90% and water use by 67% relative to the conventional feed. GHG emissions for the algae-based feed were 40% higher than those of the conventional feed, but this increase may be offset by the reduced land-use requirement (and avoided emissions from land-use change).

99. Ruiz-Lopez et al. (2014).

100. Browdy et al. (2012).

101. Bregnballe (2015).

102. Kapetsky et al. (2013).

103. Gentry et al. (2017) found that if all suitable marine areas were developed for aquaculture, approximately 15 billion tons of finfish could be grown annually—more than 100 times our projection of aquaculture demand in 2050 (140 million tons). However, the study did not filter out areas that would be uneconomic due to distance from ports, access to markets, or shoreside infrastructure—as well as environmentally sensitive areas such as coral reefs—which would limit suitable areas.

104. WorldFish's *Blue Frontiers* report (Hall et al. 2011b) used the life cycle assessment (LCA) method to examine, quantify, and compare the environmental performance of major aquaculture production systems around the world. The LCA compiled data on inputs (e.g., land, water, feed, and energy) and environmental releases (e.g., waste nitrogen and phosphorus), and evaluated the potential environmental impacts

associated with each. *Blue Frontiers* analyzed environmental impacts of 75 major aquaculture production systems that accounted for 82% of total world aquaculture production in 2008. For this World Resources Report, WorldFish and Kasetsart University updated the *Blue Frontiers* data to assess the environmental performance of aquaculture in 2010 and developed a baseline production scenario for 2050 and several alternative scenarios. Environmental impacts associated with each of the 75 major production systems, in each of the scenarios, were modeled using the LCA. As in *Blue Frontiers*, the scope of analysis was from cradle to farmgate, covering raw material production (crops, fishmeal, and fish oil), feed production, aquaculture production (farming), and water emissions (nitrogen and phosphorus). The LCA did not cover infrastructure, seed production, land-use change, packaging and processing of produce, transport of feed and produce, or waste disposal. See Mungkung et al. (2014) for more details.

105. De Silva and Soto (2009).

106. Brummett et al. (2008).

107. Umesh et al. (2010).

108. Fort (2013).

109. See, for example, Hernandez et al. (2017) on the growth of aquaculture in Bangladesh just over the past decade.

110. Global examples include the FAO/World Bank Ecosystem Approach to Aquaculture; the Assessment of Sustainable Development of Aquaculture (EVAD) initiative, led by the French National Research Agency; and the Global Aquaculture Alliance initiative on best aquaculture practices for zone management. Regional initiatives include the FAO, Asia-Pacific Fishery Commission (APFIC), and Network of Aquaculture Centres in Asia-Pacific (NACA) initiative on Sustainable Intensification of Aquaculture in Asia-Pacific; the New Partnership for Africa's Development (NEPAD) Action Plan for Development of African Fisheries and Aquaculture; and the European Aquaculture Technology and Innovation Platform.

111. See Waite et al. (2014).

112. Heldbo and Klee (2014).

## REFERENCES

To find the References list, see page 500, or download here: www.SustainableFoodFuture.org

## PHOTO CREDITS

Pg. 284 Heba El-Begawi/WorldFish, pg. 286 PXHere, pg. 292 Finn Thilsted/WorldFish, pg. 301 Peter Fredenburg/WorldFish, pg. 302 WorldFish, pg. 304 JPI Oceans.
<figure><img src="image_150.png" /></figure>
COURSE 5

# Reduce Greenhouse Gas Emissions from Agricultural Production

Agricultural production is responsible for more greenhouse gas (GHG) emissions each year than land-use change but production-related emissions are traditionally regarded as harder to control. In general, our estimates of mitigation potential are more optimistic than the estimates of other researchers, partly because many analyses have not fully captured the opportunities for productivity gains and partly because we factor in promising potential for technological innovations.

## TABLE OF CONTENTS

<table><tr><td>Chapter 24. Menu Item: Reduce Enteric Fermentation through New Technologies</td><td>315</td></tr><tr><td>Chapter 25. Menu Item: Reduce Emissions through Improved Manure Management</td><td>321</td></tr><tr><td>Chapter 26. Menu Item: Reduce Emissions from Manure Left on Pasture</td><td>333</td></tr><tr><td>Chapter 27. Menu Item: Reduce Emissions from Fertilizers by Increasing Nitrogen Use Efficiency</td><td>339</td></tr><tr><td>Chapter 28. Menu Item: Adopt Emissions-Reducing Rice Management and Varieties</td><td>355</td></tr><tr><td>Chapter 29. Menu Item: Increase Agricultural Energy Efficiency and Shift to Nonfossil Energy Sources</td><td>369</td></tr><tr><td>Chapter 30. Menu Item: Focus on Realistic Options to Sequester Carbon in Agricultural Soils</td><td>375</td></tr><tr><td>Chapter 31. The Need for Flexible Regulations</td><td>387</td></tr></table>
Introduction

GHG emissions from agricultural production pro-
cesses alone (i.e., excluding emissions from con-
verting land to agricultural use) reach 9 gigatons
(Gt) by 2050 in our baseline scenario, an increase
from 6.8 Gt in 2010 (Figure C5-1). These produc-
tion emissions arise mainly from six sources:

- “Enteric” methane emitted from the stomachs of cattle, buffalo, goats, and sheep (ruminants)

- Manure produced by some ruminants, pigs, and chickens kept in confined animal facilities (large and small)

- Unmanaged manure left on pasture and pad-docks

- Crop and pasture fertilization, particularly with nitrogen

- Rice production

- Energy use in on-farm activities and in the pro-
  duction of agricultural inputs such as fertilizer

A baseline emissions level of 9 Gt results in a GHG mitigation gap of 5 Gt relative to our target of 4 Gt of total emissions from agriculture, even if we assume that all net emissions from land-use change, including peatland degradation, are eliminated or offset (as we contemplate in some scenarios).

Our 2050 baseline already builds in many produc-
tivity gains, without which agricultural production
emissions in 2050 would rise even further (Figure
C5-1). Even with highly optimistic estimates of
changes in demand discussed in Course 1 (e.g.,
reducing food loss and waste, shifting diets to less
ruminant-based foods), annual production emis-
sions would still reach 7.2 Gt in 2050. Additional
increases in livestock productivity analyzed in
Chapter 11 would reduce production emissions to
only about 7 Gt.

To reach our target of total agricultural emissions of 4 Gt by 2050 (see Figure 2-6 in “Scope of the Challenge and Menu of Possible Solutions”), efforts to reduce agricultural production emissions will be essential. Many possible approaches would also reduce other environmental impacts of agriculture, including air and water pollution caused by manure and fertilizer.

The following chapters explore menu items that
could reduce agricultural production emissions by
changing production processes. We find that mean-
ingful potential exists today and that innovation
offers the possibility of much greater mitigation in
the future. Achieving these innovations will require
both public support for research and development
and flexible regulations that provide incentives
for farmers and the private sector to pursue cost-
effective solutions.
<figure><img src="image_151.png" /><figcaption>Figure C5-1 | Annual agricultural production emissions could reach 9 gigatons or more by 2050</figcaption></figure>

Source: GlobAgri-WRR model.
<figure><img src="image_152.png" /></figure>
# MENU ITEM: REDUCE ENTERIC FERMENTATION THROUGH NEW TECHNOLOGIES

Methane produced by digestive processes in the stomachs of ruminants—mainly cattle, sheep, and goats—is the largest source of GHG emissions from livestock. Productivity improvements will reduce methane emissions, mainly because more milk and meat is produced per kilogram of feed, but additional measures will be needed to help offset growth in demand for ruminant meat. This chapter explores technological approaches to reducing enteric methane emissions.
<figure><img src="image_153.png" /><figcaption>Figure 24-1 | Greenhouse gas emissions from agricultural production, 2010 and 2050</figcaption></figure>

## The Challenge

Livestock generate roughly half of agricultural production GHG emissions today (Figure 24-1), even when excluding the emissions resulting from feed production. In 2050, two-thirds of livestock emissions, and more than one-third of total agricultural production emissions, will be methane generated by “enteric fermentation.” This methane, which exits mainly from the animal’s mouth, is produced by the natural breakdown of forages and other feed by anaerobic microorganisms (technically archaea) in the stomachs of ruminants—cattle, goats, sheep, and buffalo.

Strategies to reduce enteric methane emissions, in addition to improving livestock productivity, rely on four approaches to manipulate the dominant microbiological communities in the rumen: using vaccines, selectively breeding animals that naturally

produce fewer emissions, incorporating special feeds or supplements into diets, and using compounds that can be thought of as drugs.

Governments have supported more research on this issue than on other sources of agricultural GHGs. Some dedicated scientific facilities are evaluating mitigation options. For example, at one New Zealand facility, scientists for years have systematically tested thousands of possible drugs or feed supplements. They start by adding compounds in small glass containers filled with rumen fluids. The most promising compounds are fed directly to animals temporarily housed in clear, tightly sealed glass chambers, which permit researchers to carefully measure the methane they release. The same chambers allow researchers to test different food additives, vaccines, and breeds to minimize methane emissions.

Unfortunately, the vast majority of results have been disappointing, mainly because the archaea that produce methane have found ways to overcome whatever initially suppresses them.¹ Although testing of animals has shown that different individual animals at different times produce very different levels of methane,² breeding has not yet produced animals that systematically generate below-average methane levels.³ Vaccines also have proven only modestly and temporarily effective.⁴ Although many feed compounds at first reduced methane emissions, most quickly lost their effectiveness. The digestion of cellulose results in a hydrogen gas that provides an energy source for microorganisms that can use it. As one paper summarized the problem, “The rumen microorganisms have the ability to adapt to foreign agents or changes in the feeding regimen and, therefore, short-term responses are not representative of the effect of a given mitigation compound or practice in real farm conditions.”⁵

A few chemical compounds have provided persistent benefits so far, such as bromoform and chloroform.⁶ These compounds are found in the red algae that make up some kinds of seaweed and explain why feeding experiments using small quantities of such seaweeds in feed, around 0.5 percent, have achieved greater than 50 percent reductions in methane emissions.⁷ Unfortunately, these compounds are associated with important animal health or environmental concerns.⁸ As a result, scientists are divided on whether to continue investigating
<figure><img src="image_154.png" /></figure>

seaweed, with researchers in New Zealand discontinuing work while some researchers in Australia and the United States continue their studies. Separately, New Zealand researchers announced the identification of five promising compounds in 2015,⁹ but peer-reviewed publications with results have yet to emerge.

As alternatives to chemical or drug compounds, some feed supplements—including vegetable oils and nitrate—have shown limited effectiveness at reducing methane emissions without health or productivity concerns.¹⁰ But the financial costs of these supplements are high relative to emissions avoided. One analysis estimated that the potential costs of mitigation using these supplements start at $100 per ton of carbon dioxide equivalent (CO₂e) and rise with higher levels of mitigation. The analysis further estimated that even at a marginal cost of $300 per ton, the potential mitigation from these feed supplements amounted to only a few percent of enteric emissions.¹¹ We consider these approaches too expensive and their emissions-reduction benefits too small to be worthy of inclusion in our menu for a sustainable food future.

## The Opportunity

Fortunately, since about 2015, at least one promising chemical feed additive has emerged. Multiple studies of cattle have shown that a small molecule, called 3-nitrooxypropan (3-NOP), generates sustained methane reductions of 30 percent or more in both cattle and sheep over at least several weeks.¹² This additive appears to have a persistent effect because the compound interferes with part of the fundamental chemical reaction that produces methane in all archaea.¹³ The fundamental nature of this pathway may also reduce the rate at which archaea can mutate around it. On the basis of existing research, the chemical appears to have no adverse effects on animal health.

There is also good evidence from 3-NOP and other studies so far that reducing methane harms neither animals nor their productivity. This testing alleviates concerns that cows might be harmed by a build-up of hydrogen in the rumen when it no longer binds with carbon to form methane.¹⁴

3-NOP may also increase meat productivity, although the results to date have not demonstrated such gains clearly. Because ruminants lose up to 12 percent of the gross energy in feed as a result of the rumen's methane production,¹⁵ reduced methane production in theory has the potential to increase productivity or reduce the quantity of feed needed. Yet studies of 3-NOP in dairy cows have not found increased production of milk, and only some have
found increases in daily weight gain (and only in dairy cows, not beef cows). Research is still ongoing, and DSM, the company that makes 3-NOP, is exploring the alternative route of maintaining output while reducing feed input.

Steps remain before 3-NOP can be broadly adopted. Researchers are still conducting experiments to obtain approval.¹⁶ DSM hopes to have 3-NOP available on the market by 2020, though problems could still emerge. Yet overall, the progress made so far increases confidence that researchers will ultimately identify a cost-effective, safe, and effective compound.

## Mitigation Potential

Although the novelty of effective compounds makes any projections uncertain, our mitigation options are based on assumptions about using 3-NOP or a comparable compound. The principal limitation of 3-NOP now is that it requires daily ingestion, and preferably frequently. In the leading study, it was mixed with feed in stall-fed dairy animals, which therefore ingest it throughout the day.

In our modeling, we assume that a feed compound will reduce emissions by 30 percent, which is the claim now being made by the producers of 3-NOP. We apply it in our first (Coordinated Effort) scenario to half of animals that receive more than a small amount of concentrated feed, which would facilitate their ingestion of a compound. In our Highly Ambitious scenario, we apply these reductions to all animals receiving concentrated feed. Under our Breakthrough Technologies scenario,

<table><caption>**Table 24-1** | Global effects of enteric fermentation reduction scenarios on greenhouse gas emissions from agricultural production</caption><thead><tr><th>SCENARIO</th><th>ENTERIC<br>FERMENTATION<br>EMISSIONS<br>(MT CO<sub>2</sub>E)</th><th>TOTAL<br>PRODUCTION<br>EMISSIONS<br>(MT CO<sub>2</sub>E)</th><th>PRODUCTION<br>EMISSIONS GHG<br>MITIGATION GAP<br>(GT CO<sub>2</sub>E)</th></tr></thead><tbody><tr><td>2010</td><td>2,260</td><td>6,769</td><td>—</td></tr><tr><td>No productivity gains after 2010</td><td>4,432</td><td>11,251</td><td>7.3<br>(2.3)</td></tr><tr><td>2050 BASELINE</td><td>3,419</td><td>9,023</td><td>5.0</td></tr><tr><td>30% methane emissions reduction (animals receiving half of concentrated feeds) (Coordinated Effort)</td><td>3,126</td><td>8,730</td><td>4.7<br>(-0.3)</td></tr><tr><td>30% methane emissions reduction (all animals receiving concentrated feeds) (Highly Ambitious)</td><td>2,807</td><td>8,411</td><td>4.4<br>(-0.6)</td></tr><tr><td>30% methane emissions reduction (all ruminants) (Breakthrough Technologies)</td><td>2,393</td><td>7,997</td><td>4.0<br>(-1.0)</td></tr></tbody></table>

Notes: Numbers not summed correctly are due to rounding. Numbers shown in parentheses are changes relative to 2050 baseline.

Source: GlobAgri-WRR model.
the feed compound and associated 30 percent emissions reduction is assumed to apply to all ruminants including those permanently grazed. We make this assumption only in that scenario because such an achievement would likely require additional technological innovation to develop ways of delivering 3-NOP or alternative compounds, such as long-lasting, slow-release additives (Table 24-1).

The three mitigation scenarios lead to a reduction of enteric fermentation emissions of between 9 percent and 30 percent relative to our 2050 baseline. They would close between 6 percent and 20 percent of the production emissions GHG mitigation gap.

## Recommended Strategies

Governments first need to continue their support for developing compounds to reduce methane from enteric fermentation. Without such support, the opportunities are less likely to be realized.

Researchers and corporations also need to know that if they develop a measure that provides cost-effective mitigation, it will be used. It is possible that compounds like 3-NOP will eventually pay for themselves through reduced need for feed or increased productivity, but they also might not, and cost-effective mitigation benefits should be considered sufficient justification to require their use.

We therefore recommend that governments provide incentives to the private sector by promising to require use of compounds if and when they prove to mitigate emissions at a reasonable cost. A first step could require use of such compounds as a condition of receiving farm subsidies. Because this recommendation applies to several mitigation strategies, we elaborate more on it in the final chapter of this course.

<figure><img src="image_155.png" /></figure>
<figure><img src="image_156.png" /></figure>
# MENU ITEM: REDUCE EMISSIONS THROUGH IMPROVED MANURE MANAGEMENT

The breakdown of manure by microorganisms under waterlogged conditions generates both methane and nitrous oxide emissions, which are powerful GHGs. Concentrated manure presents many other environmental challenges: it compromises water quality, contributes to local and regional air pollution, harbors pathogens, and generates noxious odors. This menu item focuses on ways to reduce GHG emissions from managed manure—but the same measures that reduce GHGs also tend to mitigate other environmental problems.
<figure><img src="image_157.png" /><figcaption>**Figure 25-1** | Greenhouse gas emissions from agricultural production, 2010 and 2050</figcaption></figure>

## The Challenge

Livestock produce vast quantities of manure. Manure is “managed” when ruminants, pigs, or poultry are raised in confined settings and farmers remove manure and dispose of it in some way. (The manure that cattle, sheep, and goats deposit on grasslands and paddocks is considered unmanaged, and we address emissions from this source in the next menu item.) Manure begins to emit GHGs immediately after it is deposited in the barn where animals are kept,¹⁷ but the majority of emissions occur in the manure storage system.

## Dry and wet manure management systems

Some manure is managed in “dry systems,” in which farms allow the urine to partially dry where it falls before scraping and piling the manure. Dry systems are found in virtually all poultry facilities because low volumes of urine leave poultry manure naturally dry. In the case of cattle and pigs, partial saturation of pockets of manure by urine creates the kinds of low-oxygen, high-carbon conditions that, when present for a day or more, are ideal for the microorganisms that produce nitrous oxide. More permanently saturated pockets tend to generate methane. Although the majority of the world’s managed manure is managed dry, dry manure produces roughly 40 percent of global manure management GHG emissions (using estimates generated by the Global Land Evaporation Amsterdam Model [GLEAM] developed by the Food and Agriculture Organization of the United Nations [FAO]),¹⁸ mostly in the form of nitrous oxide. Dry systems also result in high losses of nitrogen in a variety of forms, which reduces the nutrient value of the manure and typically generates abundant ammonia, an air pollutant.

Roughly 60 percent of managed manure emissions occur in “wet systems,” in which farmers collect both feces and urine and sometimes add some water to flush manure into storage areas. These storage systems can take a variety of forms. When farmers use relatively small pits dug out of the earth, which they must empty several times a year, they are often called pits or slurries. When farmers use much larger dug-out pits, they are called “lagoons.” These storage systems provide ideal conditions for archaea to generate methane. Per ton of manure, wet systems generate on the order of 20 times more methane than dry-managed manure, according to guidance from the Intergovernmental Panel on Climate Change (IPCC) and more recent studies.¹⁹ Dry systems produce far more nitrous oxide although they have lower total emissions. When and if farmers ultimately apply wet manure to cropland and pasture, the manure also generates emissions, but we count and discuss those emissions as part of “soil fertilization,” which we address in Chapter 27.
<figure><img src="image_158.png" /></figure>

## Managed manure volumes and emissions

We estimate GHG emissions from managed manure at nearly 590 million tons (Mt) of CO₂e in 2010. We project that these emissions will rise to 770 Mt CO₂e in our 2050 baseline (Figure 25-1). Of this total, we estimate that roughly one-third is in the form of nitrous oxide and two-thirds is in the form of methane.

Our estimates and projections are similar to those of other researchers. Perhaps because all global managed manure estimates use some form of guidance from the IPCC, seven of eight estimates recently summarized ranged only from 470 to 590 Mt CO₂e for recent years.²⁰ In all studies, the estimated emissions from methane are very similar.²¹ Differences arise primarily in estimates of nitrous oxide emissions. There is also evidence from a meta-analysis of available field data that IPCC emission factors are too low, at least for dairy cows in developed countries, which would suggest higher total global emissions.²²

Although estimates are rough, estimates by FAO using the GLEAM model indicate that manure from

pigs is responsible for half of all managed manure emissions, primarily through methane generated in wet systems. Dairy cows generate around one-third of all emissions, roughly evenly divided between methane and nitrous oxide. Beef operations produce roughly one-sixth of all GHGs, primarily through nitrous oxide, because their predominant manure management systems are dry. Poultry produce relatively low GHG emissions (although they tend to generate abundant ammonia) because their wastes are dry enough to inhibit production of nitrous oxide or methane.

The critical question is what farmers can do to mitigate emissions from managed manure. More efficient production has only modest effects on managed manure emissions, unlike most other sources of agricultural emissions. To date, global estimates of technical—let alone economic—mitigation potential tend to be modest. For example, one review estimated the potential at 100 Mt CO₂e per year.²³ Such a level would mitigate only around one-sixth to one-eighth of present estimates of emissions from managed manure. Although we are ultimately more hopeful, we too consider mitigating managed manure emissions to be challenging for three reasons:
First, because most manure managed under dry systems generates relatively low emissions per kilogram of manure,²⁴ any control technology must be fairly inexpensive if it is to be cost-effective.²⁵

Second, one-third of managed manure emissions today take the form of nitrous oxide, which is harder to control than methane—and this share is likely to rise by 2050.²⁶ Nitrous oxide emissions occur when manure is moist but not in liquid form and starts to occur as soon as wastes are deposited by the animal.²⁷ We discuss below opportunities to use solid separation on pig and dairy farms, but, in dry beef operations and many smaller farms, the main strategy suggested in the literature is to reduce overfeeding of protein (and therefore nitrogen) to livestock. In some countries, farmers feed excess protein, so reductions are practicable. In advanced systems, feed can more closely match the specific amino acid needs of livestock.²⁸ But in large parts of the developing world, livestock underconsume protein. Even where cows consume more nitrogen than they need, reducing protein in feed may result in more methane emissions from manure management through a complex and poorly understood microbial interaction.²⁹ In addition, efficiency gains in consumption of nitrogen by animals are mostly tied to the overall efficiency of feeding, and our baseline analysis already assumes substantial increases in overall feeding efficiency.

Third, farmers cannot practically influence many of the factors that influence emissions. For example, emissions from stored manure can be much higher in warmer climates than cool climates.³⁰ But strong economic factors influence where farmers raise animals, so it generally would be expensive, and socially and politically challenging, to shift livestock production to cooler areas just to reduce GHG emissions. Managed manure emissions also increase the longer farmers store manure before spreading it on farm fields. But spreading manure more frequently would often mean fertilizing crops when they cannot use the nutrients and thus increasing water pollution and nitrous oxide emissions in the field.

## The Opportunity

Despite these challenges, we see greater potential for mitigation if countries take reasonable steps to advance manure-management technologies. There appears to be abundant opportunity for innovation. Even existing technologies appear capable of reducing emissions at a cost equal to only a small percentage of the price of meat and milk and at an acceptable cost per ton of emissions.

In this section, we discuss the opportunities for controlling managed manure emissions with a simple technology, solid separation, that can mitigate emissions from wet and dry manure alike and can grow in complexity and levels of mitigation as required. We then consider some lessons from research into manure management at a North Carolina pig farm, which offer insight into the potential to develop truly sophisticated manure management systems. Finally, we discuss digesters, which have received much of the manure management focus. They have potential to improve manure management but also present risks if not properly managed.

## Separating solids, liquids, and nutrients

Separating liquids from solids is a relatively simple measure to reduce emissions and improve manure management generally. Since the solid portions of manure are drier after separation, they are likely to emit somewhat less methane. The liquid portion also causes fewer emissions because its lower carbon content gives microorganisms less to feed on and turn into methane.

Even without government incentives, a wide variety of systems already exist that can separate solids and, in the process, improve potential use of manure's nutrients. The simplest systems use gravity and a series of grates or ponds to let solids settle out. Many dairy farms in the United States use these systems. But mechanical systems can include screw presses or centrifuges that squeeze or whisk water out of solids and greatly increase the extent of the separation. Use of chemical "flocculents," which cause small particles to bind together, can increase removal rates of solids to 75-90 percent or higher, and can remove nearly all the phosphorus. More advanced systems use a variety of techniques to strip out nitrogen and phosphorus.
Separating liquids from solids also helps segregate
nutrients; more nitrogen tends to remain with the
liquid and more phosphorus stays with the solids.
Two waste streams make it possible to better direct
nitrogen and phosphorus to fields that need them.
The phosphorus content of manure tends to be
particularly high relative to local field needs, so
concentrating and drying out phosphorus in solids
makes it cheaper to transport the manure to fields
that can benefit from it.³¹

The degree of GHG mitigation that separation can
achieve will probably vary according to the type of
farm and the extent of the solid separation. Stud-
ies to date use modeling assumptions rather than
real field data. One study of pig farms in China
found that solid separation would reduce emissions
by more than half compared to even a basic dry
management system (which mixes manure with
straw), mostly by reducing nitrous oxide emissions.
If compared to storage of manure in a deep pit,
solid separation systems would reduce emissions by
two-thirds.³²

Achieving large reductions requires more than a
low level of solid separation achieved by simple
gravity-fed, grated systems. For example, a study of
manure management changes on large dairy farms
conducted for the California state government
estimated only an 11 percent reduction in methane
using solid separation.³³ But this study assumed
that only 15 percent more solids would be sepa-
rated, which would require only simple systems of
solid separation.

One analysis of dairy farms in the United States
estimated the cost of simple separation systems
at only about $5–$6 per cow per year, with more
advanced systems costing $50–$75 per cow per
year.³⁴ A cost of $75 per cow in the United States is
roughly equivalent to only 1 cent per liter of milk,³⁵
and these systems can still potentially pay for
themselves because they save other costs of manure
management, including hauling costs, and because
they enable more valuable use of nutrients.³⁶ One
analysis of dairy farms in Iowa found that farms
using advanced solid separation actually had the
lowest manure management costs.³⁷ To indicate
the potential, some dairy farms in Michigan and

New York have installed a system that uses reverse
osmosis to clean up effluent almost to drinking
water standards for reuse. Although the system is
expensive, the farm owners believe it will ultimately
save them money, mainly by lowering hauling costs
and making more valuable use of nutrients.³⁸

With good, daily solid separation, perhaps half or
more of remaining emissions will result from the
storage of solids, perhaps in equal parts methane
and nitrous oxide.³⁹ These emissions can be reduced
by the use of chemical additives to inhibit nitrous
oxide emissions, some of which have proven effective
at least during composting.⁴⁰ Other approaches that
may improve performance and reduce costs include
integrating systems into initial barn design and con-
struction that help separate urine, which is high in
nitrogen, from feces, which are high in phosphorus.⁴¹

Although solid separation receives relatively little
attention in the mitigation literature, it represents
both a good technology for initial implementation
and one that farmers are likely to improve over
time. It has many characteristics that make it prom-
ising across multiple farms:

- Because even simple separation can help to reduce emissions, solid separation is not an all-or-nothing strategy. Opportunities exist for incremental improvements, which in turn create opportunities for the kinds of small-scale innovations that tend to push down costs.

- Unlike some technologies, small farms should be able to employ solid separation because the technology should scale up or down according to the size of the farm and the costs will depend mainly on the quantity of manure.

- Solid separation is a pretreatment technology for almost all other likely advanced manure management techniques, whether designed to reduce emissions or other air and water pollution problems.

- Once systems are installed, farmers will have incentives to make them work well to reduce hauling costs and to increase the value of the use of nutrients.
## Mitigating manure managed as a liquid

Manure that is currently stored as a liquid in lagoons or smaller storage facilities presents the largest opportunities for mitigation because the manure provides a concentrated source of emissions. Based on GLEAM data, wet manure generates 90 percent of pig farm emissions globally. Studies and experience with manure management systems for pig farms in the U.S. state of North Carolina illustrate the potential, given some financial encouragement (Box 25-1). In that state, roughly $15 million of research and development funding, distributed competitively, resulted in development of a sophisticated wastewater system that would virtually eliminate not just GHGs but all other forms of air and water pollution, odor, and disease risk. The system should add only around 2 percent to the retail price of pork.⁴² These technologies emerged without the advantages of “learning by doing” or economies-of-scale production. They suggest that with more incentives, broader application, and without the need to meet such stringent standards for other pollutants, variations in liquid manure technology would likely emerge at even lower costs.

## Digesters and covered storage

Advanced manure management has focused much of its attention on systems that “digest” manure, so these systems merit special attention here. One lesson from substantial work to date is that digesters have promise for manure already managed in wet systems but are unlikely to reduce overall emissions from manure otherwise managed in dry systems. A second lesson is the critical importance of controlling leaks wherever digesters are used, whether low-technology digesters in poorer countries or higher-technology digesters in rich ones.

Digesters typically confine liquid manure without oxygen to generate and capture methane, which is then often burned to provide heat or to make electricity. Digesters can be large and simple (e.g., lagoons covered with plastic tarps), large and more sophisticated (e.g., various forms of metal tanks), or small and simple (e.g., small clay or brick structures). In developed countries, where digesters are mostly large, the gas is typically used to run an electric turbine or cleaned of its many impurities and fed into a natural gas grid. These steps greatly

raise the cost despite the energy they generate. For a 700-cow dairy operation in the United States, the overall costs of installation including the electricity-generating turbine may be $4 million. Operating costs can be high—as much as the annualized cost of the installation.⁴³ By contrast, household-level digesters in developing countries typically feed the gas back for use by the households, which is inexpensive and provides a cheaper, easier, and cleaner source of energy than wood or charcoal—even if the gas contains impurities that would fail the standards of most grid systems. The vast majority of the world's digesters are in developing countries, with 7 million in just five large Asian countries.⁴⁴

Digesters were generally developed not to reduce GHG emissions but to provide energy and to reduce odor and organisms that cause disease. Whether they reduce emissions depends on how much they leak and whether farmers would otherwise manage their manure wet or dry. With no leaks in either the digester or in transport and use of the gas, a digester and its ultimate use should eliminate all the methane and convert it to carbon dioxide, a much less potent GHG. But leaks raise concerns. The IPCC accounting guidance establishes a high, default emission factor for digesters of 10 percent of the methane-producing potential of the manure. In addition, the liquid “digestate” that comes out of the digester is itself stored in a covered form and continues to generate methane. Unless this digestate is itself captured and its methane recovered, it can add leakage of an additional 10 percent or more of the total methane produced by the digester.⁴⁵

In contrast to the IPCC standard leakage rates of 10–20 percent from digesters, the IPCC estimate of methane emissions from manure stored in dry form is 4 percent. As a result, switching from dry storage to a leaky digester would increase methane emissions (and the reduction in nitrous oxide emissions would typically not make up the difference).⁴⁶ At typical leakage rates, even factoring in use of the energy to displace fossil fuels, switching from dry manure to wet manure managed by a digester is likely to increase emissions.⁴⁷

By contrast, the IPCC default emission factors for wet manure systems are much higher. The standard emission rate for a lagoon, typically a large earthen pond, is around 70 percent of the methane-producing potential of the manure in the lagoon. The
BOX 25-1 | The opportunities for improved manure management on North Carolina pig farms

Eastern North Carolina experienced massive growth in large-scale pork production in the 1980s and 1990s. The management of manure in large, open lagoons contributed to a wide array of local problems including obnoxious odors, air pollution, nitrogen enrichment, pathogens, and dangerous algal blooms in North Carolina's principal estuary. Large fish kills occasionally occurred when lagoons broke or were flooded. a

After legal action from the state government, the principal pork producer and pig purchaser in the state agreed to provide $15 million to fund research into "environmentally superior" manure management technologies under the supervision of North Carolina State University. It also agreed to implement any such technologies found to be economically feasible by the university. Reflecting the many other concerns about manure, the criteria for "environmentally superior" were stringent but unrelated to climate change: technologies must substantially eliminate all pathogens, threat of nutrient pollution, odor, and air pollution.

The project's conclusions in 2006 were in one sense a disappointment because the university found that no technologies qualified as economically feasible. Yet the economic analysis for the study assumed that pork facilities in North Carolina alone would implement these technologies, so anything more than trivial costs would put them at a competitive disadvantage with farms in other states. The study did not analyze whether requiring all pork producers in the United States to control their pollution would be economically advantageous.

Review of the findings of that study indicates that even an extraordinarily sophisticated, tank-based manure management system would cost-effectively reduce GHG emissions without even factoring in the other pollution-reduction benefits. This system employed a series of tanks to separate pollutants, flocculent chemicals helped to achieve high levels of solid separation, and alternating tanks with and without oxygen drove out the nitrogen. b Although the system in effect employed the most advanced technologies of sewage waste management, we estimate from the project's documents

that the system would mitigate emissions at a cost of only $22 per ton of CO₂e, while eliminating 99 percent of the methane emissions. c Costs for other manure management systems studied, ranging from simple covering of lagoons to more complex digesters, ranged from $12 to $55 per ton of CO₂e, excluding any GHG savings from fossil fuel use and any economic value of the solid material left over after digestion. d If judged in relation to the mitigation costs that will be involved in meeting global GHG emissions targets, these costs are not high. In fact, the GHG reduction could be considered free from a social perspective, although not to the pork producers, because of the large cobenefits from reduced water and air pollution, odor, and risk of disease.

If all pork producers were required to implement these manure management measures, they would add most of the additional cost to the product price. However, the cost of the tank system for an average farm would represent 1.4 to 2.5 percent of the average retail price of pork over the past six years in the United States. That cost is much smaller than the fluctuations in pork prices during this time. e

Notes:

a. National Geographic (2014).

b. Oxygen tanks turn other forms of nitrogen into nitrate, and tanks without oxygen break down the nitrate into nitrogen gas.

c. Costs for the treatment technology are from Vanotti et al. (2013) and are provided per pig in the form of SSLW/year (steady state live weight per year). Griffing et al. (2004) Table 50, estimated methane emissions at 21,353 kg/1,000 pigs of 45 kg weight average. At the most recent 100-year global warming potential (GWP) of 34, that translates into 726 tons CO₂e. Zering et al. (2013) estimate costs of the "tank system" on a large pig farm in North Carolina at $158 per SSLW/year and costs for more typically sized farms ranging from $202 to $280 per SSLW/year. The unit dollars per 1,000 SSLW translates into dollars per 10 pigs of this weight. As a result, manure management systems capable of handling 100,000 SSLW are needed to address these emissions of 726 tons, which equals 100 x $158 or $15,800 per year. Assuming 99 percent abatement of methane, this calculation results in a cost estimate of $22 per ton and even assuming abatement of only 95 percent only increases that cost to $23 per ton.

d. This figure uses the same method as above except it uses digester costs based on Zering et al. (2006) and updated by communication with Kelly Zering, November 3, 2016.

e. USDA/ERS (2015b) averages annual prices from 2010–15.
<figure><img src="image_159.png" /></figure>

emission rate for a smaller “slurry tank” is around 35 percent. As a result, switching from wet manure systems to digesters should reduce emissions, even if digesters have 10–20 percent leakage rates.

Even so, the benefits are not certain. Digesters produce energy more efficiently if they combine manure with food waste, so this is a common practice. Because this food waste typically would generate less methane if left alone in a landfill—the combination of digesting manure and food waste will likely lead to higher overall methane emissions from even a moderately leaky digester.⁴⁸ Fortunately, studies show that leakage rates from sophisticated digesters can be kept to a few percent.⁴⁹ If those low leakage rates are achieved, digesters can achieve large mitigation benefits.⁵⁰

In developing countries, where the vast majority of the world's digesters are located, the GHG benefits are especially contingent on controlling leaks. In typical, simple digesters, methane is likely to leak from the input and output components and from cracks in systems that are not well maintained.⁵¹ Because the biogas is typically used directly by households, biogas production sometimes exceeds household needs and is deliberately vented to avoid

harm to the digester. Studies in the south of Vietnam estimated these intentional releases at 34 percent of the biogas (and therefore of the methane), while a study in the north of the country estimated intentional releases at only 7 percent. Because the alternative manure management system is likely to be dry storage, the potential for savings from the use of digesters in manure management alone is doubtful.

Yet even in these systems, the potential for overall GHG savings exists if the biogas replaces coal or wood harvests as a source of energy or enables more efficient use of the manure as fertilizer. Factoring in these nonmanure benefits, one study estimated that even quite leaky digesters could reduce overall emissions on small farms in Asia.⁵² Digesters also provide important cobenefits, including reduced disease-bearing organisms, improved water quality, and replacement of inefficient indoor stoves—which reduces unhealthy indoor smoke and wood cutting. One Chinese study used scanning devices to detect household-based digesters and observed lower leakage rates than those generally found in other Asian studies (although the study probably did not capture intentional venting).⁵³ This finding suggests that inspection systems may be feasible and could help identify and reduce leakages.
Overall, the lesson is that digesters could provide a viable means of controlling manure management emissions—particularly using more sophisticated digesters to control wet manure—but only if they are properly managed to control leaks both from the digester itself and from the storage of the digestate liquid that comes out of the digester.

In addition to the leakage challenge, the large up-front costs of installing sophisticated digester systems tend to inhibit their use. The main costs relate either to the turbine and related components if the biogas is used to generate electricity, or to cleaning the biogas so that it can be used as natural gas in developed countries. A simpler alternative is to cover a lagoon or storage pit with an impermeable plastic cover and to capture the gas and burn it. Doing so converts methane to carbon dioxide, which has a much smaller warming potency. The cost is more modest in part because a cover helps reduce hauling costs by reducing the addition of rainwater. Cost-effectiveness also increases with larger operations.⁵⁴

## Model Results: Mitigation Potential

Any effort to properly evaluate the costs of mitigating GHG emissions from manure must start with the enormous environmental and social problems presented by badly managed manure. Leaking storage systems contribute to groundwater pollution and drinking water problems.⁵⁵ In China, the world's largest producer of pork, some 30–70 percent of manure is discharged directly into water bodies without any treatment, creating the primary source of pollution that causes algal blooms and dead zones in the South China Sea.⁵⁶ The southeastern United States experienced massive flooding during Hurricane Florence in September 2018, when at least 60 hog farm lagoons overflowed, releasing contaminated water into surrounding communities.⁵⁷ Ammonia also contributes to serious air pollution problems.⁵⁸ Manure carries disease-bearing organisms that pose health risks, and ammonia emissions often contribute substantially to small-particle air pollution, a major source of ill health in humans and animals. And large feedlots often cause major odor problems for surrounding communities, which can even be unhealthy.

These concerns, not GHG emissions, have to date driven most efforts to improve manure management. Health concerns and the need to mitigate the impacts of climate change together justify more vigorous action to manage manure effectively.

We used GlobAgri-WRR to test three GHG emissions mitigation scenarios for managed manure (Table 25-1). Although the mix of farm systems changes between 2010 and 2050, our 2050 baseline projection assumes that the share of each type of manure management system for each type of farm remains unchanged. Based on our analysis above, we believe that 90 percent reductions in methane are possible from wet manure systems. For dry manure pork production systems, the study of pig farms in China described earlier suggests that 60 percent reductions in nitrous oxide emissions (but no change in methane emissions) are achievable with good solid separation.⁵⁹

Less research has been conducted into dry beef and dairy systems, so the evidence is not clear. However, dry systems tend to leave manure uncollected for long periods in feedlots, and there is evidence that collecting and distributing the manure more frequently can reduce nitrogen losses by 20–30 percent.⁶⁰ Although we do not expect large gains from animal dietary changes, we believe that 10 percent reductions in nitrous oxide from feed changes are plausible. Based on these considerations, we develop the following scenarios:

- In our first scenario, we assume mitigation of 40 percent of the methane from manure that is managed in wet form.

- In a second scenario, we assume that all farms, including both wet and dry manure farms, reduce their total manure management emissions by 20 percent. We include this scenario for perspective but consider it less realistic.

- In our most optimistic scenario, we assume 80 percent reduction of emissions of methane from wet manure, 20 percent mitigation of methane emissions from dry manure, and 20 percent mitigation of nitrous oxide emissions from all manure.

These scenarios reduce emissions from managed manure (relative to 2050 baseline) by 13 to 37 percent.
<table><caption>Table 25-1 | Global effects of manure management scenarios on agricultural greenhouse gas emissions</caption><thead><tr><th>SCENARIO</th><th>MANURE<br>MANAGEMENT<br>EMISSIONS<br>(MT CO<sub>2</sub>E)</th><th>TOTAL<br>PRODUCTION<br>EMISSIONS<br>(MT CO<sub>2</sub>E)</th><th>PRODUCTION<br>EMISSIONS GHG<br>MITIGATION GAP<br>(GT CO<sub>2</sub>E)</th></tr></thead><tbody><tr><td><strong>2010</strong></td><td><strong>588</strong></td><td><strong>6,769</strong></td><td>—</td></tr><tr><td>No productivity gains after 2010</td><td>972</td><td>11,251</td><td>7.3<br>(2.2)</td></tr><tr><td><strong>2050 BASELINE</strong></td><td><strong>770</strong></td><td><strong>9,023</strong></td><td><strong>5.0</strong></td></tr><tr><td>40% reduction in methane emissions from wet manure<br>(Coordinated Effort)</td><td>673<br>(-13%)</td><td>8,925</td><td>4.9<br>(-0.1)</td></tr><tr><td>20% reduction in manure management emissions across all farms<br>(Illustrative, not included in any combined scenario)</td><td>617<br>(-20%)</td><td>8,869</td><td>4.9<br>(-0.2)</td></tr><tr><td>80% reduction in wet manure emissions, plus 20% reduction of all<br>other manure management emissions (Highly Ambitious, Breakthrough<br>Technologies)</td><td>489<br>(-37%)</td><td>8,742</td><td>4.7<br>(-0.3)</td></tr></tbody></table>

Notes: Numbers not summed correctly are due to rounding. Numbers shown in parentheses are changes relative to 2050 baseline.

Source: GlobAgri-WRR model.

<figure><img src="image_160.png" /></figure>
## Recommended Strategies

We make a number of specific recommendations:

**Build spatial databases of large concentrated livestock facilities.** Information about manure management is remarkably rough because in most of the world there has been no effort to map and identify the types and levels of manure management systems used, even on large livestock operations. That not only frustrates analysis but also inhibits action. By contrast, Denmark not only tracks information on every substantial pig and dairy farm but tracks each animal as well. As a first step, governments need to develop reasonable data on each sizable livestock operation and its manure management system.

**Adopt regulations immediately to require improved manure management on all new farms, as well as on all medium and large concentrated livestock farms that currently use wet manure management systems.** New livestock farms can more easily incorporate at least basic solid separation into their design. Even in parts of developing countries without power, farms can use gravity systems to help separate solids and liquids. Standards should be extended to increasing numbers of existing farms over time. In this way, sounder manure management by 2050 should be feasible.

Many of the farms that manage manure in wet form are relatively large, commercial operations,⁶¹ particularly pig farms. In the U.S. pork industry in 2012, for example, just 13 percent of pig farms held 2,000 or more pigs, but these farms held 87 percent of all pigs nationally.⁶² These farms should also be required to meet the standards for new operations. Based on the technology analysis in North Carolina, governments of wealthier countries should require that farms emit methane and other pollutants at no more than 10 percent of the rate of today's standard facilities. To avoid placing facilities at a competitive disadvantage, regulations should be adopted at the national or regional level. Large food companies should also adopt standards to require proper manure management by their suppliers.

**Phase in regulation of all existing livestock operations with managed manure systems, focusing on livestock purchasers.** One goal of any regulatory system should be to find the

cheapest options for mitigation first, which allows technology to improve and become cheaper before addressing more expensive challenges. For manure management, this would likely entail imposing regulations on larger wholesale operations and requiring increasingly large percentages of their product over time to come from farms certified as meeting higher manure management standards. For example, in the United States in 2012, five large firms controlled 62 percent of the nation's pig slaughtering capacity.⁶³ To facilitate this ratcheting up of standards, the government could issue certificates to farms that meet different standards of emissions per kilogram of meat or milk or, if easier, per animal. Wholesalers would then be required to hold certificates sufficient to demonstrate that they meet increasingly stringent targets of emissions per kilogram of meat or milk. Wholesalers would pass on the bulk of these costs to consumers and reimburse the costs borne by producers who meet manure management standards by purchasing certificates. Such a system would encourage improved management by those farms that could do so at the least cost. If such a system assigned more credit to farms that meet higher standards of performance, it could also create powerful incentives for innovation and improvement wherever cost-effective.

**Adopt competitive programs to encourage new technology.** The challenge in manure management is often just to refine mechanical and chemical engineering approaches for handling manure. These are engineering challenges well suited to the capabilities of the private sector, which can build upon waste-treatment technologies already developed for industrial wastes and municipal sewage. Governments can play a role by establishing competitive grants programs for private companies, based on criteria such as cost, environmental performance, and promise of technological improvement.

**Adopt inspection systems to monitor digester leaks.** For manure management systems using digesters, particularly in developing countries, governments should require future use of digester technologies with lower leakage potential. In addition, governments should adopt inspection systems that use methane detectors to monitor leaks.
<figure><img src="image_161.png" /></figure>
# MENU ITEM: REDUCE EMISSIONS FROM MANURE LEFT ON PASTURE

Manure deposited by cattle, sheep, and goats on grazing lands or in paddocks can concentrate nitrogen in carbon-rich, saturated conditions that encourage the production of nitrous oxide by microorganisms. Manure consists of both feces and urine, and, in general, urine contains most of the nitrogen and generates nitrous oxide at a greater rate than feces. Reducing emissions from pasture manure is challenging because sources are diffuse; biological and chemical nitrification inhibitors hold the most promise.
<figure><img src="image_162.png" /><figcaption>Figure 26-1 | Greenhouse gas emissions from agricultural production, 2010 and 2050</figcaption></figure>

## The Challenge

According to standard emission factors used by the IPCC, nitrogen deposited in feces and urine turns into nitrous oxide roughly twice as fast as nitrogen in fertilizer. According to FAO (reported in FAOSTAT), these deposits, all from ruminants, are rising rapidly, contributing 800 Mt CO₂e emissions in 2010 and 846 Mt CO₂e in 2014. Our estimate, using GlobAgri-WRR, is substantially lower at 446 Mt CO₂e in 2010, and we project emissions of 653 Mt CO₂e by 2050 (Figure 26-1). FAO bases its estimates on the number of animals, assuming the same emissions per animal, whereas GlobAgri-WRR uses a method based on estimated nitrogen in excretions from different animals based on what they eat. Regardless of which source is used, these emissions are on a course to be substantial in 2050, and even our lower projection would contribute 16 percent of the total allowable emissions from agriculture (4 Gt target) in 2050.

As with enteric methane, one way to reduce emissions from unmanaged manure is to improve efficiency; that is, to improve the output of product per animal and per kilogram of feed. Under our “no productivity gains after 2010” scenario, emissions from unmanaged manure would reach 871 Mt CO₂e in 2050 (Figure C5-1), but our baseline estimates 25 percent fewer emissions due to the efficiency gains built into our baseline. Our Course 2 scenario that involves a higher efficiency target for livestock (discussed in Chapter 11) could reduce these emissions only modestly to 630 Mt in 2050. Even our 30 percent reduction in ruminant meat consumption scenario (Chapter 6) would only reduce these emissions to 524 Mt in 2050. Finding additional ways to reduce these emissions is therefore necessary.

## The Opportunity

Other studies typically estimate little to no global potential to mitigate this source of diffuse emissions.⁶⁴ We are more optimistic, but our optimism rests on further development of some technologies that have shown good potential but are not yet ready for deployment. They focus on “inhibiting” the formation of nitrate.

Livestock deposit nitrogen primarily in the form of urea (CH₄N₂O). Through biochemical processes mediated by bacteria and archaea in soils, urea is typically converted into ammonia (NH₃), ammonium (NH₄⁺), and then nitrate (NO₃⁻). Nitrous oxide (N₂O) is primarily released by the bacteria that break down nitrate in waterlogged conditions, and, although the quantity is small, the warming effect is great because of the potent warming effect of nitrous oxide. Because nitrate is soluble in water and does not adhere to soils, it is also the primary form of nitrogen that runs off of fields or leaches into groundwater, causing water pollution. Inhibiting the formation of nitrate in soils reduces both losses of nitrogen through water runoff and leaching and emissions of nitrous oxide.

## Spreading nitrification inhibitors

One way to reduce these emissions involves spreading chemicals that inhibit nitrification directly on pastureland. Most experiments have used dicyandiamide (DCD), the most commonly used inhibitor. A summary of six experiments using DCD on grazing land found reductions in nitrous oxide ranging from 17 percent to 88 percent.⁶⁵
<figure><img src="image_163.png" /></figure>

Inhibitors do not persist in their effects, however, particularly under higher temperatures, so a one-time application is not sufficient. In New Zealand, the practice has been to spread the inhibitor twice per year, each time shortly after animals are moved away from a field, when grass is grazed down and farmers can directly apply the inhibitors to the urine patches, which typically cover 20 percent of a field.⁶⁶ One study in the warmer parts of New Zealand suggested that three applications per year would be needed to achieve high effectiveness there because of a higher breakdown rate. Although bacteria might be able to develop resistance to inhibitors, no studies have yet shown this effect.⁶⁷

The practicality of using inhibitors in this way also depends on the size of fields and on the effects of inhibitors on grass yields. Inhibitors are most likely to be practical and economical on farms such as dairy farms in New Zealand, where intensive, rotational grazing is practiced on generally well-watered, highly managed fields, and where grazing is concentrated in relatively small areas. Research studies in New Zealand have typically found positive effects of inhibitors on grass yields from 15 to 36 percent, although these studies are not necessarily representative of real, commercial operations.⁶⁸ Other studies in both New Zealand and the United Kingdom have found no beneficial effect on pasture yield, which suggests variability in inhibitor performance.⁶⁹ Use of inhibitors is likely to be less practical on more extensively managed grazing lands, although these lands will receive less manure and therefore produce fewer emissions per hectare.

## Feeding nitrification inhibitors

An alternative approach to inhibiting nitrification involves feeding inhibitors directly to animals. A few studies have found that adding inhibitors to water or livestock feed provides effective reduction of both nitrous oxide emissions and nitrogen leaching, and that most of the inhibitor passes through the animal in the urine.⁷⁰ This method would be easier than pasture application and would probably require less inhibitor to be effective.⁷¹ However, the inhibitor would probably need to be ingested frequently, even daily, by the animals.

Feeding inhibitors through water or feed does raise health issues. Although toxicological studies of DCD have found very low toxicity,⁷² the lack of an agreed international safety standard caused New Zealand to suspend use of DCD in 2013 after trace levels were found in milk.⁷³ One New Zealand study also found that DCD washed off into freshwater ecosystems, where it might affect natural nitrification rates.⁷⁴ These concerns need to be thoroughly researched for any nitrification inhibitor, although the low toxicity ratings of DCD so far suggest that it could satisfy these health and environmental concerns.

## Breeding biological nitrification inhibition

A third opportunity involves breeding and selecting grasses that inhibit the conversion of ammonium to nitrate, which is the first step in the process of generating nitrous oxide. Many studies have now found extremely low rates of nitrous oxide formation in fields of *Brachiaria humidicola*, which is one variant of the African *brachiaria* grass family used extensively in Brazil.⁷⁵ This “biological nitrifi-
cation inhibition” appears to be due in small part to stronger root uptake of nitrogen but in larger part to a chemical exuded by the roots of the grass (brachialactone), which blocks a key enzymatic pathway in the formation of nitrate. The production and exudation of this chemical varies widely among plants, but it has been found at significant levels in another *brachiaria* species (*Brachiaria decumbrens*).⁷⁶ It is also plausible, although not yet tested, that cattle consuming one of these grass species will excrete some of the chemical in their manure, which would also help to inhibit nitrous oxide production.

The results suggest in part that more widespread use of *Brachiaria humidicola* could reduce emissions. But this species is useful only in tropical and subtropical areas. It constitutes only a small percentage of total *brachiaria* use in Latin America, and its preferential use compared to other species depends on many agronomic factors. For grazing purposes, the alternative is to breed this inhibitory effect into other grass species.

## Mitigation Potential

An important question for estimating mitigation potential is whether the present emission factors used by the IPCC are too high. The IPCC Tier 1 sets an emission factor of 2 percent of nitrogen in manure turning into nitrous oxide, which is double the rate assumed for fertilizer and is based on older measurements in temperate countries. A variety of recent evidence suggests lower rates. Because emissions require a high level of soil saturation, emissions factors in hotter and drier climates, where urine patches dry out quickly, should be substantially lower, which is the finding of several recent studies.⁷⁷ Even in wetter, temperate countries, some studies are finding lower emission factors, for example in New Zealand and the United Kingdom.⁷⁸

Despite this evidence, there is a growing discrepancy between field-level estimates of nitrous oxide emission rates, studies that use flux towers, and studies that use modeling based on patterns of nitrous oxide sensed in the atmosphere by satellites.⁷⁹ It is already difficult to reconcile IPCC emission factors with measured global nitrous oxide levels, and estimated emissions rates that are lower than IPCC figures—whether from pasture or cropland—would create larger inconsistencies.

One likely explanation is that the rates vary greatly depending on a range of soil and temperature conditions. There are also likely hotspots—areas that are more frequently saturated or that have the right acidity, which result in large releases of nitrous oxide.⁸⁰

These differences could present an opportunity. Identifying hotspots would allow mitigation to focus on them. Mitigating nitrous oxide emissions from manure deposited on extensive grazing lands in arid regions would be difficult because urine patches will be spread over large areas, farmers do not provide daily feed supplements, and farmers do not use planted grasses. If evidence continues to confirm low emission rates from extensive grazing in more arid areas,⁸¹ mitigation in these areas could be ignored. Mitigation efforts could then focus on more intensive grazing systems in wetter areas.

Overall, although promising technological approaches exist to mitigate nitrous oxide emissions from grazing operations, they all are too little developed to allow refined estimates of mitigation potential. We exclude additional mitigation in our Coordinated Effort scenario because all progress relies on some degree of technological improvement. We also assume that mitigation on arid grazing land will be economically or practically unfeasible because the emissions are too low to justify the expense of addressing them. We assume mitigation improvements on wetter grazing lands of 20 percent and 40 percent in our Highly Ambitious and Breakthrough Technologies scenarios, respectively. Finally, for illustrative purposes, we show one scenario with 60 percent mitigation on wetter grazing lands (Table 26-1).

## Recommended Strategies

Because solutions for this source of emissions are underdeveloped, research and regulatory incentives have to focus on ways to develop them.

### Increase research funding

The most obvious recommendation is that governments and research agencies should substantially increase research funding into methods for reducing nitrification of nitrogen on pasturelands. Three initiatives are appropriate:
<table><caption>Table 26-1 | Global effects of scenarios of emissions reductions from manure left on pasture on agricultural greenhouse gas emissions</caption><thead><tr><th>SCENARIO</th><th>NITROUS OXIDE EMISSIONS FROM PASTURE, RANGE, AND PADDOCK (MT CO<sub>2</sub>E)</th><th>TOTAL PRODUCTION EMISSIONS (MT CO<sub>2</sub>E)</th><th>PRODUCTION EMISSIONS GHG MITIGATION GAP (GT CO<sub>2</sub>E)</th></tr></thead><tbody><tr><td>2010</td><td>446</td><td>6,769</td><td>—</td></tr><tr><td>No productivity gains after 2010</td><td>871</td><td>11,251</td><td>7.3 (2.2)</td></tr><tr><td>2050 BASELINE and Coordinated Effort</td><td>653</td><td>9,023</td><td>5.0</td></tr><tr><td>20% reduction of nitrogen left on wetter pastures (Highly Ambitious)</td><td>584</td><td>8,954</td><td>5.0 (-0.1)</td></tr><tr><td>40% reduction of nitrogen left on wetter pastures (Breakthrough Technologies)</td><td>515</td><td>8,884</td><td>4.9 (-0.1)</td></tr><tr><td>60% reduction of nitrogen left on wetter pastures (illustrative, not included in any combined scenario)</td><td>445</td><td>8,814</td><td>4.8 (-0.2)</td></tr></tbody></table>

Notes: Numbers not summed correctly are due to rounding. Numbers shown in parentheses are changes relative to 2050 baseline. Coordinated Effort scenario assumes no reduction in nitrous oxide emissions relative to levels projected in the 2050 baseline.

Source: GlobAgri-WRR model.

- **Research into development and uses of nitrification inhibitors.** Virtually all published research on their use in pastures comes from a few small research groups in New Zealand. Other countries need to expand these efforts.

- **Research into biological nitrification inhibition.** Analysis of biological nitrification inhibition is currently being undertaken by a small cooperative effort of four research institutions coordinated by the Japan International Research Center for Agricultural Scientists and the International Maize and Wheat Improvement Center. Not counting the salaries of participating researchers, the budget for their research is roughly $1 million per year.⁸² A budget of tens of millions of dollars would be the minimum appropriate for this research given its level of importance and the many ways additional research could be performed.

- **Research on agricultural emissions rates.** As the discussion above indicates, it is likely that emissions rates of nitrous oxide vary greatly from one area to another and are concentrated in certain hotspots. Although some research shows these effects, it is not systematic. Field analyses have become cheaper, however, and can be combined with measures from tall towers and satellites. The world needs a comprehensive, international initiative to identify these hotspots and emissions rates.

## Create private regulatory incentives

Opportunities also exist to craft regulations that give incentives to industry to develop workable new technologies by guaranteeing them a market. For example, governments could promise to require use of nitrification inhibitors on an increasing percentage of farms if industry could demonstrate products or technologies that achieve a specified level of nitrous oxide reduction at a specified cost per ton of nitrous oxide saved. We elaborate on these regulatory opportunities at the end of this course.
<figure><img src="image_164.png" /></figure>
MENU ITEM: REDUCE
EMISSIONS FROM
FERTILIZERS BY
INCREASING NITROGEN
USE EFFICIENCY

Less than half of the nitrogen added to crop fields is absorbed by crops and the remainder contributes to emissions and other forms of nitrogen pollution. This menu item involves increasing the efficiency of nitrogen use, in significant part by focusing on the composition of fertilizers themselves, to reduce both the quantity of fertilizer required and associated emissions.
<figure><img src="image_165.png" /><figcaption>Figure 27-1 | Greenhouse gas emissions from agricultural production, 2010 and 2050</figcaption></figure>

## The Challenge

Although fertilizing crops with nitrogen, phosphorus, and potassium—the major nutrients—is vital to achieving high crop and pasture yields, it also contributes substantially to GHG emissions. Using GlobAgri-WRR, we estimate fertilizer emissions in 2010 at 1,289 Mt CO₂e, of which 94 percent resulted from nitrogen use (Figure 27-1). Two-thirds of these nitrogen emissions were in the form of nitrous oxide emitted in crop fields from all forms of applied nitrogen; the other one-third came from the energy used in the manufacture and transportation of nitrogen fertilizer (Figure 27-2).⁸³ (Because

fertilizer production is so energy-intensive, and because more efficient nitrogen use would substantially reduce these emissions, we discuss emissions from fertilizer manufacture both in this menu item and in our menu item focused on ways of reducing fossil energy use.) Synthetic fertilizer accounts for roughly half of all nitrogen fertilization,⁸⁴ the other half comes from manure applied to crops (excluded from manure management calculations), the residues of nitrogen-fixing crops such as soybeans, nitrogen in rain, irrigation water and air dust; and even nitrogen fixed by freely associated microorganisms in soil.

Fertilizer (mineral and organic) also contributes to a variety of other environmental challenges. These include small particulate smoke and smog (technically ground-level ozone), which are the leading air pollution problems for human health.⁸⁵ Agricultural runoff is the principal cause of unsafe levels of nitrate in drinking water from wells or rivers in many areas in the world. When nitrogen runoff or leachate into rivers reaches coastal waters, it can contribute to algal blooms, some of which are toxic to fish and other sea life. Other algal blooms lead to hypoxia—a condition where coastal waters have little or no oxygen—also called “dead zones.” Both types of blooms have been increasing in size and frequency and now contaminate large portions of major water bodies such as the Gulf of Mexico, the Chesapeake Bay, and the China Sea during certain seasons. Figure 27-3 maps 762 overfertilized coastal waters around the globe.⁸⁶ Phosphorus runoff also contributes to algal blooms and dead zones in lakes and rivers and in brackish coastal waters, which mix fresh and saltwater.⁸⁷ One estimate suggested that alleviating the nitrogen contribution to environmental problems would require reductions in nitrogen losses to the environment of roughly one-half.⁸⁸
<figure><img src="image_166.png" /><figcaption>**Figure 27-2** | Approximately 94 percent of emissions from fertilizing soils are the result of nitrogen application</figcaption></figure>

*Note:* This chart excludes emissions from manure left on paddocks and pasture, discussed above, and differs from FAOSTAT estimates in part because GlobAgri-WRR is based on nitrogen estimates underlying Zhang et al. (2015b) and nitrogen availability in manure from a livestock management component based on Herrero et al. (2013).

*Source:* GlobAgri-WRR model.

<figure><img src="image_167.png" /><figcaption>**Figure 27-3** | More than 700 "dead zones" exist in the world's coastal waters</figcaption></figure>

*Note:* Eutrophic water occurs when water bodies are oversupplied with nutrients and support rich plant and algal growth. Hypoxic water occurs when abundant plants and algae die and decompose, consuming oxygen and depriving other aquatic life of oxygen.

Maps are for illustrative purposes and do not imply the expression of any opinion on the part of WRI concerning the legal status of any country or territory, or concerning the delimitation of frontiers or boundaries.

*Source:* WRI (2013).
Increasing food production implies a growing demand for fertilizer and higher associated emissions and pollution. How much higher depends on how efficiently crops use nutrients. On a global basis, estimates of the efficiency with which crops absorb the nitrogen (from all sources) added to croplands range from only 42 to 47 percent.⁸⁹ As Lassellatta et al. (2014) found, this nitrogen use efficiency (NUE)⁹⁰ actually declined from around 68 percent to 47 percent between 1961 and 1980 as farmers around the world adopted synthetic fertilizers, and it has remained roughly at that level since.⁹¹ Put another way, more than half of the nitrogen applied to crops is lost to the environment.

Countries differ greatly in both their NUE (Figure 27-4) and rates of nitrogen fertilizer application per hectare (Figure 27-5). Regions group into four broad categories. At one extreme, most countries in sub-Saharan Africa use little fertilizer, and whatever fertilizer they use is more fully absorbed by crops, leading to an average NUE of 72 percent and above.⁹² At the other extreme, China and India—which accounted for 80 percent of the global increase in total nitrogen use between 2000 and

2009—generally overapply fertilizer and have NUEs of roughly 30 percent.⁹⁴ In a third category, a few developed countries, such as the United States, Canada, and France, have NUEs approaching 70 percent. In the fourth category is the rest of the world which has NUEs of around 50 percent.⁹⁵

Rising NUEs in some regions and for some crops inspire confidence that increases in NUE are both possible and practical. The Netherlands, for example, cut back its nitrogen use from an astonishing level of around 600 kg per hectare in the late 1970s to around 300 kg in more recent years, mostly by exporting or processing some of the manure from the country's dairy farms instead of spreading it excessively on farm fields.⁹⁶ France, whose agriculture is more focused on crops, applies fertilizer at only a little more than half the per-hectare rate of the Netherlands. Total fertilizer application rates per hectare in France have remained stable now for many years. Yet yields in France have increased, meaning that fertilizer use per ton of crop has decreased, and NUE has increased from roughly 30 percent in the late 1970s to approximately 70 percent in 2010.⁹⁷ Nitrogen use efficiencies have also

<figure><img src="image_168.png" /><figcaption>Figure 27-4 | The percentage of applied nitrogen that is absorbed by crops varies widely across the world</figcaption></figure>

Note: Absorption rates greater than 100 percent mean crops are mining nitrogen from soils. Maps are for illustrative purposes and do not imply the expression of any opinion on the part of WRI concerning the legal status of any country or territory, or concerning the delimitation of frontiers or boundaries.

Source: Zhang et al. (2015b).
<figure><img src="image_169.png" /><figcaption>Figure 27-5 | Total nitrogen fertilizer application is heavily concentrated in China, the United States, India, and Western Europe</figcaption></figure>

Note: Maps are for illustrative purposes and do not imply the expression of any opinion on the part of WRI concerning the legal status of any country or territory, or concerning the delimitation of frontiers or boundaries.

Source: Mueller et al. (2012).

been growing in the United States, from roughly 60 percent in 1990 to around 70 percent in 2010, according to one study.⁹⁸

Despite these improvements, there are reasons not to be overly optimistic about potential reductions in nitrous oxide emissions from fertilizer use.

First, in Africa, nitrogen use efficiency is likely to decline. The region's farmers today apply so little fertilizer that the annual removal of crops depletes the soils of nitrogen and phosphorus.⁹⁹ As farmers in Africa apply more fertilizer, which is necessary to boost yields, plants will be less able to absorb all the nitrogen and nitrogen use efficiency will decline.

Second, although Zhang et al. (2015b) showed that nitrogen use efficiency has stopped declining in most countries, and has improved in some, it has yet to start improving in most countries.

Third, major agronomic reasons help to explain the wide differences in NUE among countries. One reason China's NUE is so low is that it produces large quantities of rice and vegetables, which have low NUEs. Rice NUEs are low in part because the

flooding and drainage required for paddy rice leads to increased nitrogen loss, while fruit and vegetable NUEs are low probably because their high economic value makes it economical for farmers to apply more nitrogen even when it leads to only modest additional production. According to Zhang et al. (2015b), half of the difference between NUEs in China and the United States is explained by China's crop mix.¹⁰⁰ In addition, farmers in countries with greater rainfall variability and less rich soils will find it harder to use nitrogen efficiently because crops will not be able to fully absorb available nitrogen in bad rainfall years. These differences help to explain why countries with similar yields for the same crops have different NUEs.¹⁰¹

Even for farming regions such as the U.S. corn (maize) belt that have achieved large increases in NUE, those increases have still been insufficient to reduce nitrogen losses to the environment because nitrogen used for higher production exceeds the nitrogen saved through higher efficiency.¹⁰² Despite increases in NUE since 2005, U.S. agricultural nitrous oxide emissions have increased by 7 percent,¹⁰³ and the corn belt remains a global