沙漠研究 21-2, 57 -61 (2011)“ICAL 1/DT X”

Journal of Arid Land Studies-Refereed Article-Using Carbon Reforestation for Water and Environmental Restoration
Richard HARPER*1), Keith SMETTEM2), Stanley SOCHACKI1), Yasuhide NAKAGAMI3), Shinichiro HONDA3),Fumio TAKAHASHI4), Kunio KAWAMOTO4) and James BULINSKI5)
Abstract: A range of environmental problems including loss of biodiversity, desertification, and compromised water quality persist
across many arid and semi-arid environments despite a good technical understanding of both the processes involved and likely
solutions. Reforestation is an emerging method of carbon mitigation and this carbon investment may thus provide a means ofaddressing these environmental problems and achieving landscape scale changes. A possible negative outcome of large scaleland-use change may be depletion of food production. In south-western Australia several approaches have been used to integrate
carbon mitigation with food production and to value the various environmental services (e.g. water quality and yield, carbon
mitigation) produced from reforestation. This paper describes three case studies: (1) a large-scale commercial carbon reforestation
scheme project which integrates strips of eucalypts with cereal farming, (2) reforestation of salinized and abandoned farmland and (3)watershed scale modeling that uses an existing hydrologic model to predict water yield and quality impacts of reforestation.
Although reforestation is also likely to result in other environmental benefits these are often not valued. In contrast, where hydrologic
models exist, these allow the valuation of water benefits. In the latter example, the value of several products of reforestation (wood,carbon, water) were assessed and compared to the value of products from the existing farming system.
Key Words: Biodiversity, Carbon mitigation, Payments for environmental services (PES), Salinity, Watershed management

1. Introduction
Several approaches can be taken to reduce overall carbon
emissions, including increasing energy efficiency,
replacement of fuel sources, renewable energy and land-use
change (Pacala and Socolow, 2004). One form of land-use
change is reforestation of farmland, and this can be used toachieve carbon mitigation, via either sequestration or thereplacement of fossil fuels. Sequestration is encompassed
in Article 3.3 of the Kyoto Protocol (Schlamadinger andKarjalainen 2000) and features as a activity in several
national and voluntary emissions trading schemes.
There are several intractable environmental problems insemi-arid areas that can be managed through reforestation,
including hydrologic imbalances resulting in salinization,soil erosion, biodiversity loss from overgrazing anddeterioration of water quality. In many jurisdictions, there
is insufficient capital to implement the changes that arenecessary.
The scale of future carbon mitigation
investment may be large, and herein lies an opportunity touse carbon reforestation to tackle water and environmental
problems at a landscape or regional scale (Harper et al.
2007). This analysis evaluated the economics of carbon
sequestration and suggested it could take the form of forests
established to restore landscape hydrology, windbreaks tocontrol soil erosion, and plantings to enhance biodiversity
and provide habitat for local fauna.
Two emerging issues however require specificconsideration. The first is the potential for negative aspectsof large-scale carbon reforestation, including the competition
for farmland and thus food production. This replays someof the debates which have occurred in the past withreforestation and the reduction of water yields fromwatersheds (Calder, 2005). This discussion has been
particularly strong in Australia (Mitchell and Harper 2011).
One approach is to consider integrating trees into farming
systems (Harper et al., In Press) so as to maintain both foodproduction and achieve carbon mitigation, or to use
abandoned or low value land (Sochacki et al., In Press).
A second issue is of valuing the co-benefits anddrawbacks from reforestation. If reforestation achieves arange of outcomes, it can be argued that it is inequitable that
only the carbon should be valued, and that the other benefits
are not valued. Similarly, the costs of not undertaking
restorative action can also be valued. An economic
framework should provide a basis for rational decision
making and payments for environmental services (PES) is a
rapidly evolving area (Costanza et al., 1997; Barbier, 2007).
In this study we describe the approaches to these
problems – optimizing and valuing carbon mitigation, foodproduction and water and environmental co-benefits – that(Received June 2nd, 2011; Accepted October 10th, 2011)* Corresponding Author: r.harper@murdoch.edu.auAlcoa Chair of Sustainable Water Management, Env. Science, Murdoch University, WA, Australia 6150.
1) Murdoch University

3) Kansai Electric Power Company

2) The University of WA

4) KANSO Technos

have been developed in Western Australia(WA). This region is characterized byFig. 1. Location of the three case study sites (1-3) across thesouth-west of Western Australia.

infertile soils, a Mediterranean climate and the accumulationof salts within deep regolithic profiles. In this region,extensive development of land occurred in the period
1950-1980, with this involving the removal of natural
eucalypt dominated vegetation and its replacement withdryland farming systems. These involve cereal cropping(wheat, barley) usually in rotation with grazing systems ofannual legume based pastures (Burvill, 1979). An
extensive range of land degradation problems havedeveloped, including salinization as a result of an inducedhydrologic imbalance (Peck and Hatton 2002), wind erosion(Harper et al., 2010), and biodiversity loss (Myers et al.,2000). The approaches developed here are applicable toother semi-arid areas in the world.

2. Methods
Three case studies are examined. These occur within
three distinct areas of the agricultural zone of WA (Fig. 1).
2.1. Case study 1 - Carbon mitigation using agroforestry
strips.
One approach to achieving both hydrological benefits
and carbon sequestration is to establish strips of trees acrossthe landscape, with the continuation of food production, in
this case cropping, between the tree strips. Several shortstature eucalyptus species, termed mallees, are used in asystem that was initially developed to provide a means forthe hydrological management of salinity (Robinson et al.,2006).
Kansai Electric Power Company engaged KANSOTechnos to undertake a reforestation project through the Oil
Mallee Company of Australia as an agent in the Kalannie

region of WA (Fig. 1). This project has involved theestablishment of 10-20 m wide strips of mallee eucalypts
interspersed with cereal cropping of varying widths in anarea with around 300 mm/year annual rainfall. The aims of
the reforestation have been to abate greenhouse gas
emissions through sequestering carbon in long-term (>30years) environmental plantings.
Three species of mallee eucalypts (E. kochii spp.
plenissima, E. loxophleba spp. lissolphloia, E. horistes) wereestablished in June 2003 across 30 discrete farms, with 893
ha in total. Trees were measured in June 2010 using
permanent forest sampling plots. Tree attributes measured
included height and diameter of stems. Biomass andsequestered carbon were estimated from proprietary
allometric equations.
2.2. Case study 2 - Carbon mitigation and repair ofabandoned land.
Large areas (potentially over one million hectares) ofland have become salinized across the region, and the land is
no longer used for agricultural purposes. This project
involved the establishment of several salt-tolerant species ona salinized area near Wickepin (Fig. 1). The aims of thisreforestation have again been to achieve carbon mitigation
via either carbon sequestration or the production of biomass
for co-firing for electricity production, and the stabilizationof soils and hydrology in the salinized area (Sochacki et al.,
In Press). However, it is considered unlikely that such
reforestation will restore hydrology (George et al., 1999).
2.3. Case study 3 - Carbon mitigation combined withimproved water quality.
The impact of reforestation on water supplies is often
considered in terms of impacts on water yield. In specificcircumstances, such as the restoration of salinity,
reforestation will improve water quality to the extent that
previously unusable water can be utilized.
The study (Townsend et al., In Press) used as an
example the Warren-Tone, a large (408 000 ha) agricultural
watershed with between 500 to 700 mm/year annual rainfall.
Around a quarter of this catchment (105 000 ha) had beenpreviously cleared, with 25 000 ha subsequently reforested
with pulpwood (Eucalyptus globulus) plantations. Water
yield and quality outcomes of various reforestation scenarios
were estimated using LUCICAT a calibrated hydrologicalmodel (Bari and Smettem, 2006). A hydrological-land-use-economic model was constructed, and as described inTownsend et al. (In Press), this allows the costs and benefitsof different land-uses to be examined at a whole watershed
level. This bundled payments for various environmental

1007550502525Survival (%)

C sequestration (t CO2-e/ha)

750045678Age (years)

Fig. 2. Mean carbon sequestration (t CO2-e/ha) of the three
eucalypt mallee species after 7 years of growth atKalannie (Case study 1)

services (PES), and externalities, following reforestation.
These included estimates of returns from water, wood andcarbon and comparisons with the existing agriculturalproduction.

3. Results and Discussion
3.1. Case study 1 - Carbon mitigation using agroforestry
strips.
The mean tree height at seven years across all plots was
2.06 m, this exceeding the forest eligibility requirement ofKyoto compliant forests. The average current stocking was
1709 trees/ha, down from the mean original stocking of
2 378 trees/ha. Mean biomass across all sites was 14.9 dryt/ha, and estimated carbon sequestration 27.3 t CO2-e/ha.
There was marked variation in the mean performance ofthe different eucalypt species, with E. loxophleba spp.
lissolphloia having a mean yield across all sites of 42.4 ± 0.7
t CO2-e/ha, compared to values of 23.6 ± 0.7 t CO2-e/ha and23.0 ± 0.3 t CO2-e/ha for E. kochii spp. plenissima and E.
horistes, respectively (Fig. 2). There were also marked
differences in both biomass accumulation (0.1 - 42.9 dryt/ha) and carbon sequestration across sites (range 0.1 - 78.7 t
CO2-e/ha). This style of reforestation is relatively new andthese results suggest that further exploration of the different
rates of sequestration between species and with site
conditions will be profitable, particularly as these aspects canbe managed.
3.2. Case study 2 - Carbon mitigation and repair ofabandoned land.
A range of factors significantly affected both carbon
sequestration and biomass production on the salinized site
(Sochacki et al., In Press). These include hydrologicalconditions such as salinity, site factors such as slope positionand soil properties and a range of silvicultural factors such asFig. 3. Mean carbon sequestration (t CO2-e/ha) of Eucalyptus
occidentalis planted at 2,000 trees/ha at Wickepin (Casestudy 2).

species, planting density and age of the planting. Highdensity (2,000 trees/ha) plantings of Eucalyptus occidentalis
produced a mean of 37 t/ha of dry biomass (equivalent to 68
t CO2-e/ha), eight years after planting (Fig. 3). Continued
mitigation is expected as the stands mature, assuming thatgrowth is not affected by the accumulation of salt in the soil
profile (Archibald et al., 2006).
The same principle of using reforestation to both achievecarbon mitigation and land repair also applies to lands thathave been damaged by erosion, over-irrigation orcontaminated by pesticides; utilization of such land could
thus represent a major contribution to global carbon
mitigation without competing with food production.
3.3 Case study 3 - Carbon mitigation combined withimproved water quality.
A hydrological model (LUCICAT) was used to define
the relationships between reforestation/deforestation andwater yield and quality, thus providing a basis for valuing thehydrological benefits of reforestation. Various land-use
change scenarios were examined, with these suggesting that70% reforestation was required to restore stream salinity to a
potable threshold of 500 mg/L total dissolved salts (TDS)(Townsend et al., In press). Although it was estimated that
this would reduce annual water yields from 260 GL/year to237 GL/year, a response reported in other watersheds, theimportant distinction here is that water would be restored to apotable condition and thus have value.
Economicmodeling suggested that the sale of 100 GL/year of water at
AUD$150,000/GL would result in a net water value of$285/ha/year.
Reforestation was unprofitable when only wood
revenues from reforestation were considered, with a discountrate of 9.5% but was profitable at lower discount rates andwith carbon prices of at least $26 t CO2-e. Additional
income would come from the sale of timber and carbon, andthe bundled return from timber, carbon and water is more

Table 1. Agricultural returns and externalities and forestry
returns from both timber and carbon (AUD$/ha/year)
in the Warren Tone watershed (Case study 3). Net
Present Values were calculated with a discount rate of 7%.
Returns ($/ha/year)

Annual rainfall (mm/year)
500

700

Agricultural returns

150

190

Externality (salinity) costs of agriculture-50-30Net value of agriculture

100160Timber return-200-113

Carbon return354357

Water return285

285Timber + carbon + water439

529

Net benefit of forestry over agriculture

339

369

profitable than the existing agricultural system (Table 1).
The sale of potable water following reforestation could
provide a new source of income for landholders, on theproviso that there is enough reforestation across thewatershed to reach the potable threshold.

4. Conclusions
Whereas carbon reforestation can provide carbon
mitigation, different approaches such as using strips of trees
or abandoned land, may allow integration with existing
agriculture. This reforestation is also likely to result inother environmental benefits. There also appears to beconsiderable potential to increase the efficiency of mitigation
via species and site selection and silvicultural practices.
Environmental benefits are often not brought to account,mainly because of difficulties of valuing land repair andbiodiversity restoration. Both represent a future challenge.
In contrast, where hydrological models exist, these provide ameans of valuing potable water benefits both within specificwatersheds but also as a tool to evaluate different policy
options.
Bundling of the multiple environmental outcomes ofreforestation also appears promising; in this case markets arerequired for each of the bundled components. Importantly,
the carbon mitigation debate is often framed in terms ofimpacts on food production, whereas water and fiber are alsoessential commodities that are produced from the land.
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