# Ecosystems services at risk

Stephanie d'Agata

► To cite this version:

Stephanie d'Agata. Ecosystems services at risk. Nature Climate Change, 2022, 12, pp.13-14.
10.1038/s41558-021-01256-7. insu-03684631

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CORAL REEFS

Ecosystems services at risk

Climate change is threatening coral-reef-associated ecosystem services and people's well-being. Addressing direct and indirect coral reef stressors while developing pathways towards recovery and adaptations could mitigate negative impacts, especially in coastal developing countries.

Stephanie D'Agata

Coral reef ecosystems and their biodiversity are essential for people, supporting many livelihoods and associated identities worldwide. Beyond its intrinsic values, biodiversity is crucial for sustaining ecosystem processes and the continued delivery of ecosystem services on which human welfare depends: species assemblages are characterized by various functions based on their traits, which affect ecosystems' productivity and the provision of associated services¹. However, coral reef biodiversity is rapidly succumbing to climate change impacts. Marine heatwave (MHW)-induced coral bleaching and mortality are increasing in frequency worldwide, adding to the impacts of human stressors such as unsustainable fishing and pollution². In a paper published in *One Earth*, Eddy and colleagues³ documented a 50% decline of coral coverage in the past 50 years and a 50% loss of associated ecosystem services. These patterns translate into the erosion of coral-reef-associated biodiversity such as coral, fish and invertebrate species, and the loss of fisheries production globally. These, and similar trends, have stimulated a growing interest in evaluating the economic consequences of the loss of coral reefs and associated ecosystem services in the future, such as in Stoeckl and colleagues²⁴ study published in *Ecosystem Services*. There, the authors estimated the monetary value loss of coral reef ecosystem services with the expected loss of coral reefs in the Great Barrier Reef (GBR) up until 2075.

No matter the level of development of coastal countries, people's well-being and cultural health are directly associated with healthy coastal ecosystems. Coral reefs provide vital proteins and nutrients, particularly in developing coastal states where more than 50% of nutrients and proteins can come from fisheries⁵ (Fig. 1). Coral reefs support 6 million direct fishing jobs and more than US$6 billion in revenues globally⁶. In addition, coral reef barriers protect about 60 to 200 million people's homes from storm surges and waves⁵.

<figure><img src="image_3.png" /><figcaption>**Fig. 1** | **Fisher in southwest Madagascar.** Fisher in southwest Madagascar showing a fish caught using a gillnet.</figcaption></figure>

Eddy and colleagues³ used an extensive database of coral coverage based on more than 14,000 surveys on 3,500 reefs across 87 countries from 1957 to 2007. They also used additional expert surveys, numerous databases of marine species occurrences and catches, and coral-reef-associated fisheries effort data. The authors first evaluated the average global coral cover for each year, demonstrating that while the 1950 historical baseline ranged between 58% and 70% globally, it was estimated at 25% on average in 2007⁵. They subsequently estimated the loss of coral-reef-associated global catch, a provision ecosystem service. Since 1950, fuelled by seafood demand worldwide, global fishing effort has increased due to increasing human populations and improved technology. As a result, coral-reef-associated global fish catch steadily increased from 1950 and peaked in 2002 at about 2 million tons. However, since then, total coral-reef-associated catches have decreased owing to the decreasing fish abundance,

despite the increasing fishing effort. This finding is corroborated by a fishing indicator of stock abundance, the catch per unit effort (CPUE), which describes the quantity of fish captured during one unit of effort. Global coral-reef-associated CPUE peaked in 1971 and has decreased since, demonstrating the global erosion of reef fish abundance due to the loss of coral reef biodiversity and associated ecosystem productivity³.

Eddy and colleagues³ did not directly measure the loss of biodiversity and global catch with the loss of coral coverage. Instead, they chose an indirect path through species-area ecological theory, assuming a negative chain reaction between the loss of coral cover, biodiversity and available resources for fisheries. However, on local scales, loss of coral cover might not be systematically associated with decreasing total catch and CPUE⁷. Following a MHW-induced bleaching event and a substantial loss of coral cover that triggered a shift in fish assemblage in the Seychelles, fishers adapted
by targeting herbivorous fish, particularly
in newly macroalgae-dominated reefs. This
resulted in a similar and even higher average
catch and CPUE, but did also notably
change catch composition and increased
catch variability. Understanding fishers'
adaptive strategies to ecosystem services
changes under specific socio-economic and
ecological conditions is thus an area ripe for
future studies.

The loss of ecosystem services from coral
reefs cannot be attributed to a particular
single cause. Instead, various climate
change impacts in synergy with additional
human stressors have altered coral reef
integrity⁸, jeopardizing its functioning and
the well-being of people that depend on it.
Therefore, understanding the cumulative
impacts of climate and other stressors
on ecosystem services now and in the
future is of great concern and focus for
research. Stoeckl and colleagues¹ developed
a systematic evaluative framework to
assess the loss of eight ecosystem services
(for example, tourism and recreational
fishing) under two co-occurring stressors
on the GBR in Australia: climate change
and coral-eating crown-of-thorns
starfish (COTS) populations. While
climate-change-induced MHWs are
nowadays the most important threat to
the GBR, COTS, which are now subject to
strong management interventions, have
historically been responsible for about 40%
of GBR coral mortality⁴.

To estimate the loss of ecosystem services
values, Stoeckl and colleagues⁴ used benefit
transfer methodology, which involves
gathering available economic value estimates
from existing studies from one location
to approximate values at a similar site in
another location. Despite being subject
to approximation, this method has the
advantage of allowing rapid and relatively
inexpensive assessments of ecosystems
services values. Such monetary valuation is
less about finding the ultimate truth about
the value of nature or ecosystem services,
but rather aims at evaluating the relative
importance of goods and services that
humans receive from ecosystems compared
with man-made services⁹. Despite the
limits and controversy associated with

monetizing nature, it raises awareness of
the importance of ecosystems in a way that
is understood universally while facilitating
decision-making⁹. Using this approach,
Stoeckl and collaborators⁴ evaluated the
economic benefits of managing COTS
populations in the GBR under the
Representative Concentration Pathway (RCP)
8.5 climate change scenario (no curbing of
carbon emissions) compared with the RCP
2.6 scenario (in line with the 1.5 °C Paris
Agreement limit) as the baseline. They
predicted a 77% decrease of the reef condition
index between 2016 and 2075 under RCP
8.5, and a simultaneous nonlinear loss of a
little more than 30% (about AU$1.2 billion)
of summed ecosystem services monetary
values compared with the baseline. A local
management measure such as complete
control of COTS under RCP 8.5 would only
limit the loss to about 25%, slowing the rate of
decline but not the end-point⁴.

These two studies emphasize that
local interventions can do only a little if
not coupled with a solid commitment to
reducing carbon emissions to mitigate
climate change. The 1.5 °C goal is the
most favourable economic pathway in
terms of mitigating damage costs¹⁰. It
requires decarbonization of every sector
of the economy and strong international
cooperation, particularly among the
wealthiest 20 countries of the world that
represent about 80% of global emissions and
about 85% of the global economy¹¹. Tailored
to local contexts, a portfolio of management
measures to reduce local stressors and
minimize cumulative impacts on reefs
(for example, marine protected areas and
sustainable fisheries, reducing nutrients
and pollution export to coastal waters)
embedded in the Sustainable Development
Goals will be essential. Importantly,
adaptations to changing conditions to
sustain food security and livelihoods
will be vital. This is particularly true in
tropical developing countries where local
populations are highly dependent on coastal
resources. Those countries also encompass
the most vulnerable people on the planet:
they will experience the largest increase in
temperature variability, such as heatwaves,
even though they contribute the least to

climate change¹². Therefore, increasing the
climate change adaptive capacity of both
institutions and individuals/households
towards transformational adaptations and
relief is essential¹³. For example, if fulfilled,
the climate financing promise can go a
long way in supporting the social and
economic welfare of the most at-risk coastal
communities in developing countries¹⁴.

Amid the retrogressive trends on coral
reefs, some reefs — for example, in Cuba
and Malaysia — have been least impacted,
with reports indicating increased coral
cover in the recent past¹². Such reefs provide
hope and opportunities for research to
understand climate change impacts better
and inform biodiversity conservation and
social adaptation planning.

Stephanie D'Agata ID

ENTROPIE (IRD, University of La Reunion, CNRS,
University of New Caledonia, Ifremer), Saint-Denis,
La Reunion c/o IUEM, Plouzané, France.

e-mail: Stephanie.dagata@gmail.com

Published online: 3 January 2022

https://doi.org/10.1038/s41558-021-01256-7

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Acknowledgements

S.D. was funded by the Laboratory of Excellence
'Corail' (LIVELIHOOD project, grant EPHE IRD PD
A02020), France.

Competing interests

The author declares no competing interests.