Creating a Safe Operating
Space for Iconic Ecosystems
By M. Scheffer1, S. Barrett2, S. R. Carpenter3, C. Folke4, A. J. Green5, M. Holmgren6, T. P. Hughes7, S.
Kosten8, I. A. van de Leemput1, D.C. Nepstad9, E. H. van Nes1, E. T.H.M. Peeters1 and B. Walker10
Science 20 March 2015: Vol. 347 no. 6228 pp. 1317-1319. DOI: 10.1126/science.aaa3769
Although some ecosystem responses to climate
change are gradual, many ecosystems react in
highly non-linear ways. They show little
response until a threshold or tipping point is
reached where even a small perturbation may
trigger collapse into a state from which
recovery is difficult (1). Increasing evidence
shows that the critical climate level for such
collapse may be altered by conditions that can
be managed locally. These synergies between
local stressors and climate change provide
potential
opportunities
for
pro-active
management. Although their clarity and scale
make such local approaches more conducive to
action than global
greenhouse
gas
management, crises in iconic UNESCO World
Heritage sites illustrate that such stewardship is
at risk of failing.
The term “safe operating space” frames the
problem of managing our planet in terms of
staying within acceptable levels or
“boundaries” for global stressors (2).
Uncertainty is accounted for by keeping on the
safe side of such boundaries. The safe levels of
different stressors at global scales are mostly
considered independently. However, in
ecosystems a safe level for one stressor is often
strongly dependent of the level of other
stressors. This implies that if such synergies are
understood, local stressors may be effectively
managed to enhance tolerance to global climate
change (Fig 1).
1
Department of Aquatic Ecology and
Water Quality Management, Wageningen
University, NL-6700 AA, Wageningen,
2
The
Netherlands.
School
of
International and Public Affairs,
Columbia University, New York, NY
10027 USA. 3Center for Limnology,
University of Wisconsin, Madison, WI
53706 USA. 4Beijer Institute of
Ecological Economics, Royal Swedish
Academy
of
Sciences;
and
the
Stockholm Resilience Center, SE104
5
Estación
05
Stockholm,
Sweden.
Biológica de Doñana, EBD-CSIC, 41092
6
Sevilla, Spain.
Resource Ecology
Group, Wageningen University, NL6700
AA,
Wageningen,
The
7
Netherlands.
Australian
Research
Council Centre of Excellence for
Coral
Reef
Studies,
James
Cook
University,
QLD
4811,
Australia.
8
Aquatic
Ecology
&
Environmental
Biology,
Radboud
University
Nijmegen, Institute of Water and
LOCAL AND FEASIBLE. The feasibility of
managing the climate sensitivity of ecosystems
is becoming increasingly evident. Obviously,
local interventions are no panacea for the
threats of climatic change. For example,
melting of arctic sea ice with its far-reaching
ecological consequences cannot be arrested by
local management. However, ways of building
climate resilience are emerging for a variety of
ecosystems, ranging from control of local
sources of ocean acidification (3), to
management of grazing pressure on dry
ecosystems (4). We focus here on lakes, coral
reefs and tropical forests.
In lakes, warming and nutrient loading
have similar effects on the likelihood that the
ecosystem will tip into encroachment by
floating plants or into dominance by toxic
cyanobacteria (5). Experiments and field
studies on different scales revealed intricate
mechanisms that drive the synergy between
effects of warming and nutrient load, e.g.,
boosted nutrient cycling, and shifts in the
competitive advantage that favor small, rapidly
reproducing fish species, cyanobacteria and
floating plants (5, 6). While the synergy of
climate and nutrient stressors implies double
jeopardy to many wetlands, the good news is
that reducing the nutrient load can compensate
for effects of warming. For example, data from
lakes across continents and climate zones
suggest that a reduction in nutrient
concentrations by one third can compensate for
the effect of 1oC increase in water temperature
when it comes to the risk of cyanobacterial
dominance (6).
In coral reefs, resilience depends strongly
on locally manageable stressors such as fishing
pressure and water quality. For example, the
take-over of most Caribbean reefs by seaweeds was triggered by sea-urchin mortality,
but facilitated in many locations by high
nutrient loading and overharvesting of fish
functional groups that controlled the sea weeds
(7). On the Great Barrier Reef, coral recovery
rates after the 1998 bleaching event were
markedly suppressed by experimental
exclusion of herbivorous fishes (8). Local
conservation efforts can help in maintaining
and enhancing resilience, and in limiting
longer-term damage from bleaching and other
climate-related impacts.
In tropical forests, resilience is under
pressure from climate change as well as local
stressors such as deforestation, logging and fire
(9). Forests become stressed by increases in
temperature (10) and by greater rainfall
variability (4). One important near-term risk
from drought is a self-reinforcing shift to a
contrasting fire-maintained state. Recent
experiments confirm cascading effects of a
decline in canopy cover, which favor invasion
by flammable grasses (11). The removal of
trees makes the forest more fire-prone,
increasing the risk of further transition to open
woodland in dry years (11, 9). In addition,
there is a substantial positive feedback effect of
forest cover on regional precipitation, implying
that loss of forest contributes to overall
reduction in rainfall (9). Thus, maintaining a
critical mass of forested areas and preventing
opening of the closed canopy structure are
powerful tools to enhance the safe operating
space of tropical forest in the face of rising
drought risks.
WORLD HERITAGE AT RISK. In spite of
the solid scientific basis for managing climate
resilience in such ecosystems, failure to do so
is putting globally important ecosystems at
risk. We highlight crises faced by three iconic
World Heritage Areas.
The Doñana wetlands in southern Spain
provide the most important wintering site for
waterfowl in Europe. They contain the largest
temporary pond complex in Europe, with a
diversity of amphibians and invertebrates.
Despite the site’s protected status, the marshes
are threatened by eutrophication due to
pollution and reduced flow of incoming
streams, promoting toxic cyanobacterial
blooms and dominance by invasive floating
plants that create anoxic conditions in the
water. In addition, groundwater extraction for
strawberry culture and beach tourism also has
major impacts (12). Little has been done to
control these local stressors, leaving Doñana
unnecessarily vulnerable to climate change.
UNESCO has just rated this World Heritage
Site as under ‘very high threat’.
The Great Barrier Reef is the largest coral
system in the world. In response to multiple
threats, fishing has been prohibited since 2004
over 33% of the Great Barrier Reef Marine
Park, and efforts have begun to reduce runoff
of nutrients, pesticides, herbicides and
sediments from land. However, these
interventions may be too little, too late.
Approximately half of the coral cover has been
lost in recent decades (13), and the outlook is
“poor, and declining” with climate change,
coastal development and dredging as major
future threats (14). The World Heritage
Committee has warned that in the absence of a
solid long-term plan, it would consider listing
the reef as “in danger” in 2015 (15).
The Amazon rainforest is one of the
world’s great biological treasures and a vital
component of Earth’s climate system. Yet this
ecosystem is under increasing pressure from
climate change as well as local stressors such
as logging and forest fire (9). Brazil has shown
leadership by slowing down Amazon
deforestation by 70% (16), and by creating the
largest protected area (PA) network in the
world. Yet these successes are now being
partially undermined by major infrastructure
and natural resource extraction projects, and by
shifts in legislation (17).
FRAMING FOR ACTION. The evidence we
have for enhancing climate resilience of
ecosystems places direct responsibility on
governments to ensure implementation.
However, investment will only happen if costs
of refraining from activities that undermine
resilience are distributed in ways that lead to
effective action. Realizing such incentive
schedules may be challenging. However, there
are three specific reasons why building a safe
operating space for ecosystems by controlling
local stressors is more conducive to immediate
action than global control of greenhouse gases.
From global to local commons: Potential
incentives for local protection are much
stronger than those to supply the global public
good of abating greenhouse gas emissions (18),
for the same reason that countries tend to favor
adaptation over mitigation. Mitigation requires
global collective action and is vulnerable to
free riding, whereas adaptation can be done
unilaterally, with benefits accruing almost
exclusively to the country doing the adaptation.
However, iconic ecosystems also provide a
global public good. This is why they are on the
World Heritage list in the first place. In some
cases the local interventions can result in
substantial global mitigation. For instance,
slowing down Amazon deforestation made
Brazil a global leader in climate change
mitigation (16).
From high to low uncertainty: Perceived
uncertainty has often paralyzed policy (19),
and experimental evidence suggests that
uncertainty about climate change tipping points
undermines efforts to avoid crossing a
dangerous threshold (20). There is less
uncertainty on the ecosystem level than on the
global level when it comes to effects of
management options. From negative to
positive framing: Gloom and doom perceptions
may backfire to block action. Terms such as
‘extreme events’ and ‘catastrophic transitions’
may express the urgency of the matter.
However, social experiments reveal that
accounts of disastrous future effects of climate
change can invoke cognitive dissonance that
causes many people to disbelieve climate
change altogether. This response disappears if
a feasible approach to take action and abate the
problems is presented simultaneously (21). A
positive, action-oriented framing of a safe
operating space for the world’s iconic
ecosystems may help stimulate societal
consensus that climate change is real and
should be addressed.
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Acknowledgements: M.S. is supported by an
ERC-advanced grant and Spinoza award.
C.F. is supported by the Stellenbosch
Institute for Advanced Study. SRC's research
is supported by NSF. A.J.G. was supported
by a WIMEK research fellowship and S.K. by
a NWO-Veni grant 86312012. M.S., C.F. and
S.R.C. are also at the South American
Institute for Resilience and Sustainability
Studies. This work was carried out under the
program of the Netherlands Earth System
Science Centre (NESSC).
E-mail: marten.scheffer@wur.nl
Fig. 1 Schematic representation of safe
operating space. In ecosystems at risk of
collapse, safe boundaries for local stressors
such as harvest rates or pollution often
change with climate change. A local stressor
that is currently at a safe level (I), needs to be
adjusted to a lower value to keep the system
within the safe operating space in a future
climate (II).
Fig. 2. Examples of iconic ecosystems
where climate change may trigger
transitions to a different state. From top to
bottom: the Doñana wetlands, the Amazon
rainforest and the Great Barrier Reef (credits
from top to bottom: Jorge Sierra; André
Baertschi / wildtropix.com; David Doubilet,
National Geographic Creative).
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