Download forecasting the impacts of climate change on coastal ecosystems

FORECASTING THE IMPACTS OF CLIMATE CHANGE ON
COASTAL ECOSYSTEMS:
HOW DO WE INTEGRATE SCIENCE AND POLICY?
BRIAN HELMUTH∗
I.
INTRODUCTION ............................................................................. 207
II.
THE INTERTIDAL ZONE .................................................................. 210
III.
IMPACTS OF CLIMATE ON COASTAL ORGANISMS ............................ 212
IV.
FORECASTING FUTURE IMPACTS ................................................... 217
I. INTRODUCTION
There is consensus among the scientific community that the Earth’s
climate is changing at a rapid pace.1 Global average surface temperatures
have increased by approximately 0.75°C since the mid to late 1800s, 2
largely as a result of increases in greenhouse gas production by humans and
from changes in land use such as deforestation.3 Ocean temperatures have
increased,4 and widespread changes in temperature extremes also have been
observed:5 heat waves are now far more frequent, for example.6 While these
∗
B.S., Cornell University; M.S., Northeastern University; Ph.D., University of Washington.
Associate Professor, University of South Carolina, Department of Biological Sciences and
School of the Environment. The author can be contacted at [email protected].
1
See INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE, FOURTH ASSESSMENT REPORT,
CLIMATE CHANGE 2007: THE PHYSICAL SCIENCE BASIS 237, 249-50 (Solomon, et al. eds.,
Cambridge Univ. Press 2007), available at http://ipcc-wg1.ucar.edu/wg1/wg1-report.html
(last visited Dec. 14, 2007) [hereinafter IPCC REPORT]; Naomi Oreskes, Beyond the Ivory
Tower: The Scientific Consensus on Climate Change, 306 SCI. 1686, 1686 (2004), excerpted
from Naomi Oreskes, George Sarton Memorial Lecture at the Meeting of the American
Association for the Advancement of Science, Consensus in Science: How do we Know
We’re Not Wrong (Feb. 13, 2004); D. A. Stainforth et al., Uncertainty in Predictions of the
Climate Response to Rising Levels of Greenhouse Gases, 433 NATURE 403 (2005).
2
Kevin E. Trenberth et al., Surface and Atmospheric Climate Change, in IPCC REPORT,
supra note 1, at 237, 249-50.
3
Id. at 105.
4
Id. at 390-91.
5
Id. at 299-316.
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[VOL. 16.1
findings are often perceived as controversial or contentious by the general
public,7 a recent survey of climate change research papers suggests
otherwise. 8 This survey of articles published in the peer-reviewed scientific
literature between 1993-2003 and listed with the key words “climate
change” in the ISI database found that all 928 articles agreed with the
consensus statement that the Earth’s climate is changing and that humans
are contributing to this change.9 The challenge laid before the scientific
community therefore is no longer to determine if the planet’s climate is
changing, but rather to predict what and where the effects of these future
climatic alterations are likely to be, and what the magnitude of those
changes are likely to be. Moreover, it is becoming increasingly vital that
scientists work collaboratively with policy makers in order to determine
whether it is possible to ameliorate and mitigate these impacts by
forecasting their location and intensity.
Climatic changes are having documented impacts on the world’s
ecosystems, which in turn have cascading effects on human health and
society.10 Subsequently, understanding and forecasting the impacts of
climatic change on natural ecosystems, commercial crops, and livestock
have become increasingly important endeavors in the fields of ecology and
conservation biology.11 One of the most obvious effects of climate change
on human-made structures is sea level rise, which causes destruction
through erosion and the intrusion of salt water into the water table.12 In
contrast, one of the most direct impacts of climate change on non-human
organisms is the effect of changing climate on body temperatures.13 Almost
all physiological processes are affected by the temperature of an organism’s
6
Id. at 300-01, 308-09.
Press Release, Pew Research Center for the People & the Press, Partisanship Drives
Opinion: Little Consensus on Global Warming (July 12, 2006), available at http://peoplepress.org/reports/pdf/280.pdf.
8
Oreskes, supra note 1, at 1686.
9
Id.
10
Kenneth L. Denman et al., Couplings Between Changes in the Climate Systme and
Biogeochemistry, in IPCC REPORT, supra note 1, at 503-04.
11
See, e.g., Christopher D.G. Harley et al., The Impacts of Climate Change in Coastal Marine
Systems, 9 ECOLOGY LETTERS 228 (2006); Brian Helmuth et al., Living on the Edge of Two
Changing Worlds: Forecasting the Response of Rocky Intertidal Ecosystems to Climate
Change, 37 ANN. REV. ECOLOGY, EVOLUTION & SYSTEMATICS 373 (2006) [hereinafter
Living].
12
See U.S. Environmental Protection Agency, Coastal Zones and Sea Level Rise,
http://www.epa.gov/climatechange/effects/coastal/index.html (last visited Dec. 14, 2007).
13
See, e.g., Living, supra note 11, at 383.
7
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IMPACT OF CLIMATE CHANGE ON COASTAL ECOSYSTEMS
209
body,14 so increases in the frequency of extreme body temperatures will
have profound effects on rates of organism survival, reproduction, and
species range boundaries. 15
Intertidal habitats (the regions between the high and low tide lines of the
world’s coastlines) exist at the margins of both the terrestrial and marine
realms;16 thus, animals and algae in this ecosystem are subject to
environmental challenges posed by both the marine and terrestrial realms. 17
As a result, coastal organisms may serve as early warning systems for the
impacts of climate change. 18 Moreover, coastal ecosystems are of vital
socio-economic and ecological importance to humans. A 1997 study
estimated the total value of ecosystem services provided by coastal marine
habitats to be in excess of 14 trillion U.S. dollars per year: over 40% of the
world’s total.19 Therefore, understanding the future of coastal ecosystems
has major implications for human society.
In this paper I discuss the mechanisms by which climate affects the
survival and health of coastal organisms20 and summarize existing evidence
of how changing climate has already affected these plants and animals.21 I
then explore the question of how we can forecast, and perhaps mitigate, the
impacts of future climate change on coastal ecosystems.22 While there are
still many roadblocks to overcome, 23 ecological forecasting may serve as an
example of an effective bridge between the worlds of policy and science.24
14
See id. at 383-85 (describing a number of physiological responses to changes in body
temperature that have been identified in intertidal organisms).
15
Id.
16
Id. at 374.
17
Id.; see also fig.1, infra Part II.
18
Living, supra note 11, at 374. For further discussion of the unique vulnerability of intertidal
organisms to climate change, see J. P. Barry et al., Climate-related, Long-term Faunal
Changes in a California Rocky Intertidal Community, 267 SCI. 672 (1995); Harley et al.,
supra note 11; Stephen J. Hawkins et al., Detection of Environmental Change in a Marine
Ecosystem—Evidence from the Western English Channel, 310 SCI. TOTAL ENV’T 245 (2003);
Nova Mieszkowska et al., Changes in the Range of Some Common Rocky Shore Species in
Britain—A Response to Climate Change?, 555 HYDROBIOLOGIA 241 (2005).
19
Robert Costanza et al., The Value of the World’s Ecosystem Services and Natural Capital,
387 NATURE 253, 259 (1997).
20
See discussion infra Parts II, III.
21
See discussion infra Part III.
22
See discussion infra Part IV.
23
See discussion infra Part IV, notes 86-87, 93-95, 100.
24
See discussion infra Part IV, notes 88-92, 96-99.
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II. THE INTERTIDAL ZONE
Intertidal habitats are among the most physically harsh environments on
Earth.25 Forces imposed by currents and crashing waves can be immense, 26
leading to high rates of breakage and disturbance in wave-exposed regions. 27
During low tide, when organisms are exposed to air and the heat of the sun,
intertidal invertebrates (oysters, seastars, mussels, etc.), algae (seaweeds)
and marsh grasses must contend with thermal and desiccation stresses
imposed by the terrestrial environment, and changes in body temperature of
25-30°C (45-50°F) or more in a matter of hours are not uncommon.28 High
levels of siltation, 29 changes in salinity,30 and prolonged decreases in
oxygen31 or nutrients and food32 can all lead to significant physiological
stress and mortality. Importantly, many, if not all, of the factors thought to
drive the reproduction and survival of these creatures are predicted to
25
See Brian Helmuth & Mark W. Denny, Predicting Wave Exposure in the Rocky Intertidal
Zone: Do Bigger Waves Always Lead to Larger Forces?, 48 LIMNOLOGY & OCEANOGRAPHY
1338, 1338 (2003).
26
See generally id. (examining the hydrodynamic forces that exist in intertidal zones).
27
For discussions of the effects of hydrodynamic forces on intertidal species, see Emily
Carrington, The Ecomechanics of Mussel Attachment: From Molecules to Ecosystems, 42
INTEGRATIVE & COMP. BIOLOGY 846 (2002); Emily Carrington, Seasonal Variation in the
Attachment Strength of Blue Mussels: Causes and Consequences, 47 LIMNOLOGY &
OCEANOGRAPHY 1723 (2002); Brian Gaylord, Biological Implications of Surf-Zone Flow
Complexity, 45 LIMNOLOGY & OCEANOGRAPHY 174 (2000).
28
David W. Elvin & Jefferson J. Gonor, The Thermal Regime of an Intertidal Mytilus
Californianus Conrad Population on the Central Oregon Coast, 39 J. EXPERIMENTAL M ARINE
BIOLOGY & ECOLOGY 265, 268 tbl.2 (1979); Brian Helmuth, How Do We Measure the
Environment? Linking Intertidal Thermal Physiology and Ecology Through Biophysics, 42
INTEGRATIVE & COMP. BIOLOGY 837, 838 (2002).
29
See Howard L. Sanders, Benthic Studies in Buzzards Bay. I. Animal-Sediment
Relationships, 3 LIMNOLOGY & OCEANOGRAPHY 245 (1958).
30
See John Davenport & Hector MacAlister, Environmental Conditions and Physiological
Tolerances of Intertidal Fauna in Relation to Shore Zonation at Husvik, South Georgia, 76 J.
MARINE BIOLOGICAL ASS’N U.K. 985 (1996); Rui Li & S. H. Brawley, Improved Survival
Under Heat Stress in Intertidal Embryos (Fucus spp.) Simultaneously Exposed to
Hypersalinity and the Effect of Parental Thermal History, 144 MARINE BIOLOGY 205 (2004).
31
See Louis E. Burnett, The Challenges of Living in Hypoxic and Hypercapnic Aquatic
Environments, 37 AM. ZOOLOGIST 633 (1997); Robert F. Service, New Dead Zone off
Oregon Coast Hints at Sea Change in Currents, 305 SCI. 1099 (2004).
32
See Elizabeth P. Dahlhoff & Bruce A. Menge, Influence of Phytoplankton Concentration
and Wave Exposure on the Ecophysiology of Mytilus Californianus, 144 MARINE ECOLOGY
PROGRESS SERIES 97 (1996); Heather M. Leslie et al., Barnacle Reproductive Hotspots
Linked to Nearshore Ocean Conditions, 102 PROC. NAT’ L ACADEMY SCI. 10,534 (2005).
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IMPACT OF CLIMATE CHANGE ON COASTAL ECOSYSTEMS
211
change in coming decades.33 Several of these changes have already been
manifested as ecological impacts on coastal ecosystems.34
Figure 1. Intertidal Zone in Washington State (Tatoosh Island)
Intertidal organisms must contend with the rigors of the terrestrial environment
during each low tide; physical conditions thus become increasingly harsh moving
away from the low water mark. The result is a series of “zones” where one species
replaces another, with more tolerant species living higher in the intertidal zone, as
shown here. The intertidal zone thus serves as a natural ecological laboratory, and
is likely one of the first to show evidence of the impacts of climate change on
natural ecosystems.
Intertidal invertebrates and algae are ectotherms that evolutionarily
are of marine origin but must regularly contend with the terrestrial
environment during each low tide. As such they provide a unique
33
See generally Alan J. Southward et al., Long-Term Oceanographic and Ecological
Research in the Western English Channel, 47 ADVANCES IN MARINE BIOLOGY 1, 13-54
(2005) (examining the impact of climatic changes on coastal ecosystems, including effects on
biological factors such as water temperature and salinity, currents and circulation, nutrients,
and productivity).
34
Id.
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perspective on the relationships between both aquatic and terrestrial
climatic regimes and organismal physiology and ecology. Indeed,
largely because of the steep gradient in thermal and desiccation
stresses that occurs during low tide, the rocky intertidal zone has
long served as a natural laboratory for examining relationships
between abiotic stresses, biotic interactions, and ecological patterns
in nature.35
In many regions of the world, coastal organisms live in a series of bands
or “zones” in which the upper zonation limit (the upward extent from the
lower tidal level) of one species is set by physiological stress, and species
replace one another moving up the shore. 36 The species most tolerant of heat
and desiccation live at the top of these zones. 37 Because these algae and
animals are thought to live at the utmost extremes of their physiological
tolerance limits (temperatures of 35-40°C are not uncommon during low
tide), intertidal ecosystems, like coral reefs, are thought to be amongst the
first to show responses to increases in global temperatures.38
III. IMPACTS OF CLIMATE ON COASTAL ORGANISMS
The temperature of an animal’s (or plant’s) body affects virtually all of
its physiological processes,39 and therefore its reproduction, growth, and
survival.40 The rates at which enzymes function are strongly temperaturedependent, 41 and if temperatures become too high enzymes (and other
proteins) literally cook (a reaction known as denaturing).42 Conversely,
when body temperatures become too low, enzymes become sluggish and
cannot function properly.43 For many organisms scientists have a very good
understanding of the upper and lower temperature tolerances from years of
controlled experimental work, 44 and especially in recent years, scientists are
35
Living, supra note 11, at 375; see also fig.1, supra Part II.
Living, supra note 11, at 375; see also fig.1, supra Part II.
37
Joseph H. Connell, Community Interactions on Marine Rocky Intertidal Shores, 3 ANN.
REV. ECOLOGY, EVOLUTION & SYSTEMATICS 169, 171 (1972).
38
Helmuth, supra note 28, at 837.
39
George N. Somero, Thermal Physiology and Vertical Zonation of Intertidal Animals:
Optima, Limits, and Costs of Living, 42 INTEGRATIVE & COMP. BIOLOGY 780, 780 (2002).
40
Living, supra note 11, at 383.
41
Somero, supra note 39, at 782-87.
42
Id. at 786-87.
43
Id. at 787.
44
See id. See generally Living, supra note 11, at 376-85 (exploring the history of speciesspecific marine biogeographical studies, including recent studies that have documented the
impact of climate change on the biogeography of certain intertidal species).
36
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IMPACT OF CLIMATE CHANGE ON COASTAL ECOSYSTEMS
213
beginning to understand the molecular basis of these responses.45 By
matching up the physiological tolerance limits against body temperatures in
the field, scientists also have some idea of the range limits in nature.46
The geographic limits of species are sensitive indicators of the
interactions of organisms and their environment, and are likely to be among
the first signals of the impact of climate change on the biota of the planet. 47
At their geographic range limits, populations may suffer stresses that restrict
adult survival or recruitment of young.48 Whenever an organism’s
temperature exceeds its physiological tolerance, the animal dies, and if
temperatures are extreme enough the entire population may go locally
extinct.49 As climatic conditions change, geographic limits migrate toward
more benign regions where populations can survive and reproduce. 50 Thus,
the biogeographic limits of species can serve as “miner’s canaries” for the
processes of long-term climate change. 51 In recent years, evidence of such
range shifts have become more and more common. For example, a metaanalysis by Root et al. found that more than 80% of species examined
showed evidence of species range shifts.52 A recent analysis by Helmuth et
al. found that intertidal species range boundaries may be migrating by up to
fifty kilometers per decade, much faster than most recorded shifts in
terrestrial ecosystems.53
Often range shifts and extinction events can occur in unexpected
locations.54 As humans, we have a rather unique perspective on temperature
because of our rather tight regulation over the temperature of our bodies.
45
See Somero, supra note 39; George N. Somero, Linking Biogeography to Physiology:
Evolutionary and Acclimatory Adjustments of Thermal Limits, 2 FRONTIERS IN ZOOLOGY 1
(2005) [hereinafter Linking Biogeography to Physiology].
46
See Linking Biogeography to Physiology, supra note 45; David S. Wethey & Sarah A.
Woodin, Ecological Hindcasting of Biogeographic Responses to Climate Change in the
European Intertidal Zone, HYDROBIOLOGIA (forthcoming 2008) (on file with author).
47
Terry L. Root et al., Fingerprints of Global Warming on Wild Animals and Plants, 421
NATURE 57 (2003).
48
See Living, supra note 11, at 383.
49
Root et al., supra note 47, at 57.
50
Id. at 58; Living, supra note 11, at 378-82.
51
See Living, supra note 11, at 374 (explaining that, as a result of the exposure of rockyshore organisms and assemblages to both aquatic and aerial climatic regimes, these intertidal
species “may serve as early warning systems for the impacts of climate change.”).
52
Root et al., supra note 47, at 57.
53
Living, supra note 11, at 382.
54
Id.
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Like other mammals, we have a remarkable ability to thermoregulate,55 and
our physiological processes work over a very narrow range of temperatures;
increases in body temperature of just 3-4°C above normal can be deadly. 56
In contrast, most plants and animals on Earth have temperatures that are
driven by their ambient environments.57 Like pavement on a hot sunny day,
their temperatures are contingent upon the amount of solar radiation they
receive or the amount of heat they release to surrounding wind, and as a
result, the temperatures of their bodies are highly subject to changes in the
ambient air or water.58 Thus, the temperature of many nonhuman plants and
animals can be several degrees higher than the temperature of the
surrounding air due to the influence of solar radiation.59
While these organisms generally display much more flexibility in their
physiological responses, they too often live in environments that are at the
limits of their physiological tolerance limits. For example, estimates suggest
that as many as half of the world’s coral reefs have either been destroyed or
are under imminent risk of collapse. 60 While many factors have contributed
to these declines over the last half century,61 one of the most recent causes
of mortality has been coral bleaching due to slight increases in water
temperature.62 Coral animals harbor symbiotic algae (zooxanthellae) within
their tissues; these microorganisms give corals much of their color, and
55
See Eduardo E. Benarroch, Thermoregulation: Recent Concepts and Remaining Questions,
69 NEUROLOGY 1293 (2007).
56
Jonathan A. Patz et al., Impact of Regional Climate Change on Human Health, 438
NATURE 310, 310 (2005) (reporting that, during a two-week period in August 2003, there
were approximately 22,000 to 45,000 heat-related deaths in Europe, and stating that this was
“the most striking recent example of health risks directly resulting from temperature
change”); Marc Poumadére et al., The 2003 Heat Wave in France: Dangerous Climate
Change Here and Now, 25 RISK ANALYSIS 1483, 1483 (2005) (reporting 14,947 “excess
deaths” in France during the summer of 2003).
57
See Living, supra note 11, at 383.
58
Id.
59
See Helmuth, supra note 28, at 838.
60
Global Coral Reef Monitoring Network, Status of The Coral Reefs of the World 7 (Clive
Wilkinson ed., 2004).
61
See generally John M. Pandolfi et al., Global Trajectories of the Long-Term Decline of
Coral Reef Ecosystems, 301 SCI. 955 (2003) (citing overfishing and pollution as the
historically leading causes of coral reef loss, and disease and coral bleaching as the primary
causes of decline in recent decades).
62
Jordan M. West & Rodney V. Salm, Resistance and Resilience to Coral Bleaching:
Implications for Coral Reef Conservation and Management, 17 CONSERVATION BIOLOGY 956,
957-58 (2003).
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IMPACT OF CLIMATE CHANGE ON COASTAL ECOSYSTEMS
215
provide the coral host with much of its nutritional requirements.63 However,
slight increases in water temperature cause this symbiosis to break down,
forcing the zooxanthellae to leave the coral animal, causing it to have a
ghostly bleached appearance.64 In cases of prolonged or extreme exposure,
coral animals may die, either directly due to physiological stress or due to
complications from disease.65 As corals provide the basis of reef
ecosystems, their loss is enormous; their economic value to humans (in
terms of tourism and fisheries) was estimated to be approximately 375
billion U.S. dollars per year a decade ago. 66
Such direct effects of temperature on organisms are one of the most
obvious effects of climate change.67 Whenever local environmental
conditions cause the temperature of an organism’s body to exceed some
threshold tolerance level, either chronically or during an extreme event (e.g.
heat wave), the organism exhibits a physiological response.68 In extreme
cases, as with corals, the organism may die. 69 In other cases, responses may
be more subtle but no less significant. For example, on the shores of Europe,
the barnacle Semibalanus fails to reproduce when wintertime water
temperatures exceed 10°C.70 Recent evidence has shown that as a result of
slight increases in winter temperatures, the geographic range of this species
has moved 300 kilometers in France since 1872, at a rate of up to fifty
kilometers per decade. 71 Simultaneously, anecdotal evidence suggests that
an invasive species of Pacific oyster may be invading regions of Britain and
mainland Europe for precisely the opposite reasons due to its tolerance of
these slightly higher temperatures.72
The direct effects of temperature are just one of several ways in which
climate change impacts coastal species, however. The recently released
(2007) Intergovernmental Panel on Climate Change (“IPCC”) report
63
See id. at 957.
See id.
65
Id.
66
Costanza et al., supra note 19, at 256 tbl.2.
67
See Living, supra note 11, at 383-85.
68
Id.
69
West & Salm, supra note 62, at 957.
70
D.J. Crisp & B. Patel, Environmental Control of the Breeding of Three Boreo-Arctic
Cirripedes, 2 MARINE BIOLOGY 283, 283 (1969).
71
Wethey & Woodin, supra note 46.
72
Interview with Nova Mieskowska, Postdoctorate Researcher, Marine Biological
Association of the U.K., in Plymouth, Eng. (Aug. 7, 2007).
64
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estimates the total 20th century sea level rise as 0.17 meters (6.7 inches).73
This small increment has been sufficient to wreak havoc on coastlines that
are only a few inches above sea level.74 While some intertidal salt marsh
habitats may be able to keep pace with rates of erosion through the accretion
of sediment, others may not, and these may literally be drowned by rising
sea levels.75 In a similar vein, coral reefs rely on ambient sunlight to grow. 76
As growth rates decline as a result of increasing temperatures and changes
in seawater chemistry,77 many will not be able to keep pace with rising sea
levels.78 In other words, the seas may rise faster than the corals can keep
pace.
Changes in ocean chemistry are also occurring and are expected to
impact marine organisms. At the present, approximately half of the CO2
released by humans over the last 200 years is now stored in the ocean.79
While the ability of the oceans to absorb CO2 has slowed, 80 approximately
30% of current emissions is taken up by the oceans.81 As a result, the pH of
the oceans has been reduced and is expected to continue to decrease.82 These
reductions in pH have significant effects on corals and organisms with
shells.83 While we are just beginning to understand the effects of this
increased acidity on marine organisms, results suggest, for example, that the
reduced growth rate of corals may prevent them from keeping pace with
rising sea levels, essentially increasing the chances that coral reefs may
“drown” as sea levels rise. 84
73
Nathaniel L. Bindoff et al., Observations: Oceanic Climate Change and Sea Level, in
IPCC REPORT, supra note 1, at 409.
74
Id.
75
James T. Morris et al., Responses of Coastal Wetlands to Rising Sea Level, 83 ECOLOGY
2869, 2869-70 (2002).
76
See Coral Reef Alliance, Coral Reef Overview, http://www.coralreefalliance.org (follow
“Resource Library” hyperlink; then follow “Coral Reef FAQ” hyperlink; then follow “Coral
Reef Overview” hyperlink) (last visited Dec. 14, 2007).
77
GLOBAL CORAL REEF MONITORING NETWORK, supra note 60, at 21-24.
78
Id. at 23.
79
Christopher L. Sabine et al., The Oceanic Sink for Anthropogenic CO2, 305 SCI. 367, 370
tbl.1 (2004) (showing that approximately half of the anthropogenic CO2 emissions produced
from 1800 to 1994 were taken up and stored in the ocean).
80
See id. (indicating that the ocean-uptake fraction has decreased since 1980).
81
Richard A. Feely et al., Impact of Anthropogenic CO2 on the CaCO3 System in the Oceans,
305 SCI. 362, 362 (2004).
82
Id.
83
See id. at 365-66.
84
See id.
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IMPACT OF CLIMATE CHANGE ON COASTAL ECOSYSTEMS
217
IV. FORECASTING FUTURE IMPACTS
The coastal zone has served as a natural ecological laboratory for
examining the impacts of climate on natural ecosystems, and we now
understand a great deal about the mechanisms of how these systems work. 85
There is no doubt that ecological communities are complex: predicting the
impacts of climate change on natural ecosystems not only mandates that we
understand how and where climate will be altered, but also that we
understand the physiological and ecological responses of organisms. 86
Moreover, forecasting future ecological responses mandates an
understanding of how climate translates into changes at the scale of the
organism. 87 For example, it is now possible to model the body temperature
of intertidal animals using remote sensing data, data from weather stations
and coastal buoys. Therefore, using projections from global climate change
models, we can forecast temperatures in the future.88 Comparisons of model
outputs against measurements made in the field suggest that while daily
fluctuations of 25°C are quite common, errors in predictions of monthly
maxima are on the order of ~1°C.89 By comparing these measurements
against the physiological tolerances of animals, it is then possible to predict
(and hindcast) changes in the geographic ranges of animals that have
occurred as a result of shifts in climate. 90 In other words, these models can
be used to generate explicit hypotheses which can be tested (either
contemporarily or retroactively using historical data sets) under field
conditions.91 These approaches have the potential to serve as an interface
between policy and science using global climate change models, given an
85
See, e.g., Connell, supra note 37; Joseph H. Connell et al., A 30-Year Study of Coral
Abundance, Recruitment, and Disturbance at Several Scales in Space and Time, 67
ECOLOGICAL MONOGRAPHS 461 (1997); Robert T. Paine, Marine Rocky Shores and
Community Ecology: an Experimentalist’s Perspective, in 4 EXCELLENCE IN ECOLOGY 1 (Otto
Kinne ed., Ecology Institute 1994).
86
Brian Helmuth et al., Biophysics, Physiological Ecology, and Climate Change: Does
Mechanism Matter?, 67 ANN. REV. PHYSIOLOGY 177, 178 (2005).
87
See Sarah E. Gilman et al., Variation in the Sensitivity of Organismal Body Temperature to
Climate Change over Local and Geographic Scales, 103 PROC. NAT ’L ACAD. SCI. 9560
(Christopher B. Field ed., 2006); Brian S. Helmuth et al., Climate Change and Latitudinal
Patterns of Intertidal Thermal Stress, 298 SCI. 1015 (2002); Wethey & Woodin, supra note
46.
88
Wethey & Woodin, supra note 46; Gilman et al., supra note 87, at 9564-65.
89
Gilman et al., supra note 87, at 9561.
90
Living, supra note 11, at 391, 393; Wethey & Woodin, supra note 46.
91
Living, supra note 11, at 391.
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appropriate understanding of the uncertainty in the input used.92 It may be
possible to predict, for example, the most likely location for the
emplacement of a marine reserve based on the likelihood that a mortality
event will occur. Conversely, areas where mortality is certain to occur may
be “triaged” without needless expenditure of funds.
While such endeavors are possible, they, like other mathematical
approaches, involve large amounts of uncertainty at every step.93 Given the
potential for error, are such models useful? No model can capture every
intricacy of the natural world or predict every vicarious event; by necessity,
models must be presented in terms of probability and likelihood, even when
based on an underpinning of mechanism and physics. And, as has been
pointed out, models have the potential for misuse94 as is true for any other
management tool. However, the application of models requires a frank
discussion of the nature of uncertainty and the application of science to
matters of policy.
In many ways, predicting the impacts of climate change on natural
ecosystems is much like predicting the landfall and magnitude of a
hurricane. The farther from shore the hurricane is, the less certain we are of
the strength of the storm or the exact position that it will be when it reaches
shore. 95 As the storm gets closer to shore, the more confident we become in
our model predictions. The question then becomes, what should our
response be: (a) to abandon our attempts to model hurricane movement and
not worry about landfall until we have a high level of certainty of precisely
where it will land, (b) to make only qualitative predictions and to shore up
the entire coastline because hurricane prediction is difficult, or (as,
unfortunately seems to be in vogue) (c) deny that hurricanes exist at all
because we cannot model every last parcel of wind?
The answer lies at the interface of policy and science. Our
understanding of the effects of climate on natural ecosystems is quite
strong,96 as is our understanding of the physics of climate,97 and of the
92
Id. at 391-95.
See, e.g., Gilman et al., supra note 87, at 9561-63.
94
Orrin H. Pilkey & Linda Pilkey-Jarvis, Useless Arithmetic: Why Environmental Scientists
Can’t Predict the Future 22-23 (Columbia Univ. Press 2007).
95
Id. at 34-35.
96
See Denman et al., Couplings Between Changes in the Climate System and
Biogeochemistry, in IPCC REPORT, supra note 1, at 503-04.
97
See id. at 95-100.
93
FALL 2007]
IMPACT OF CLIMATE CHANGE ON COASTAL ECOSYSTEMS
219
interface of organisms with their local microclimates.98 The precautionary
principle99 would mandate that we protect the entire natural environment
and eliminate greenhouse gas production altogether;100 the opposite extreme
would call for a complete denial of the reality of climate change, and to
forge ahead with a “business as usual mentality.” Neither is realistic.
Production solutions must obviously involve compromise, and will by
necessity mandate some form of prediction and forecasting. While the
potential for misuse is very real,101 this does not invalidate the tool of
thoughtful modeling; the alternative is to forego any hope of planning for
the future with meaningful input from decades of science.
Our current challenge is to embed deterministic scientific knowledge
within a framework of probability, and to enact policy that recognizes
varying levels of uncertainty. This challenge will not be easy, but with an
open an honest dialog between scientists, policy makers, members of the
business community, and other relevant stakeholders, both economic and
ecological concerns can be realized.102
98
See, e.g., Helmuth, supra note 28 (describing the impact of climate change on intertidal
community and population ecology).
99
“The precautionary principle permits decisionmakers to avoid or minimize risks whose
consequences are uncertain but potentially serious by taking anticipatory action.” Stephen G.
Wood et al., Whither the Precautionary Principle? An American Assessment from an
Administrative Law Perspective, 54 AM. J. COMP. L. 581, 581 (2006).
100
See David Kriebel et al., Comment, The Precautionary Principle in Environmental
Science, 109 ENVTL. HEALTH PERSP. 871 (2001).
101
PILKEY & PILKEY-J ARVIS, supra note 94, at 22-23.
102
Millennium Ecosystem Assessment, Ecosystems and Human Well-Being: Opportunities
and Challenges for Business and Industry 29 (2005).
*