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Advocates for a Wild, Healthy Ocean
1300 19th Street NW
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Washington, DC 20036
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www.oceanconservancy.org
Global Climate Change and the Ocean – The Scientific Basis
Impacts on the Ocean Environment
Climate change is a significant threat to ocean ecosystems world-wide. There is unequivocal evidence
and scientific consensus that climate change is occurring at an unprecedented rate and that
anthropogenic activity is a major driver (IPCC 2007). Ecological processes and interactions will be
altered in response to the physical parameters of climate change (IPCC 2007, Parmesan 2006). The
ability of marine species to adapt to environmental change is largely unknown. A recent study
investigated the ability of mammals to evolve with current levels of environmental change associated
with climate change and they determined that the current rates of climate change are much too fast for
mammals to adapt; instead, extinctions are more likely to be accelerated (Barnosky and Kraatz 2007.
While there may be some species that benefit from climate change, highly vulnerable species that will
be negatively impacted by climate change include those species dependent upon extent of sea ice and
small isolated populations (e.g., ocean mammals, Simmonds and Isaac 2007) and those with narrow
temperature ranges or dependent on calcium carbonate structures (e.g., coral and coral-dependent
species, Parmesan 2006).
Climate change is a pressing ocean issue. The oceans play an important role in the planet’s carbon
cycle by absorbing large volumes of carbon dioxide and recycling it through various processes. This
carbon dioxide exchange is largely controlled by circulation, sea surface temperatures, and biological
processes such as photosynthesis and respiration by plankton which use carbon in the ocean in a similar
manner to plants on land. Many long-term changes in climate have been documented across the oceans
and affect its near-shore and offshore inhabitants. These include increased arctic temperatures and less
ice cover, precipitation extremes, decreased ocean salinity, increased ocean acidity, shifting current
patterns, amplified extreme events (e.g., droughts, precipitation, heat waves) and changes in marine
biodiversity and population size, movement and phenology (IPCC 2007).
Climate Change Linked to Human Activity
Carbon dioxide and other greenhouse gases have markedly increased since 1850 as a result of human
activity (IPCC 2007) (Figure 1). The 35% increase in CO2 over this period is primarily due to fossil
fuel use and changes in land-use patterns (IPCC 2007). Human-driven increases in greenhouse gases
have resulted in significant concomitant increases in atmospheric and oceanic temperatures and a
significant warming trend over the past 30 years (IPCC 2007) (Figure 2). Even if carbon emissions are
substantially reduced, CO2 levels in the oceans will continue to increase for decades (IPCC 2007).
Atmospheric CO2 levels are accelerating at rates greater than predicted because of increased carbon
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dioxide emissions and declining carbon dioxide sinks; all of which contribute to hastened climate
forcing, such as melting of polar ice and ocean acidification (Canadell et al. in press).
Figure 1.
Atmospheric
concentrations of
carbon dioxide from
1000 AD to the early
1800s were relatively
stable. Atmospheric
CO2 has increased
exponentially because
of human activity
since the industrial
revolution around
1850. The area
enlarged within the
inset is the CO2 data
samples taken and
made famous by
Charles Keeling at
Mauna Loa, Hawaii
(Sarmiento and
Gruber 2002).
Figure 2. There has been an increase in
global surface warming and if CO2
atmospheric concentrations are not reduced
substantially, global temperatures will only
increase further. The average global surface
warming (in degrees Celsius) observed since
1900 are to the left of the perpendicular line
with the projected warming from the year
2000 to 2100 to the right of the line for
different emission scenarios. Emission
scenarios range for rapid economic growth
(e.g. A1B) to ones that envision reductions
in energy use (e.g. B2), and, for comparison,
scenarios based on constant emissions.
Shading denotes the ±1 standard deviation
range around the annual averages. (IPCC
2007).
Ocean Warming
The ocean drives earth’s climate and is
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one of the first, and often unnoticed, casualties of increased emissions of greenhouse gases. Over 80%
of the excess heat produced by the greenhouse effect has been absorbed by the ocean, as evidenced by
a rise in global ocean temperatures of 0.1 degrees Celsius in the upper 700m between 1961 and 2003
(IPCC 2007) (Figure 3). While this may seem like a relatively small number, physiologically and
ecologically, this number has significant effects on ocean organisms (Figure 4). Rising ocean
temperatures will result in a cascade of physical and ecological effects. Water temperature is an
important determinant of physiological function of ocean organisms, and is, ultimately, an important
feature of distribution and ranges of species and habitats. Even more alarming is a widening tropical
belt and the poleward movement of large-scale climate systems (e.g., jet streams and storm tracks),
which could have profound effects on ocean circulation and all ocean ecosystems and organisms
(Seidel et al. in press).
Figure 3. Global ocean heat
content (0 – 700m depth) has
been increasing in time. The
different colored lines,
which represent independent
analyses of oceanographic
data, show a strong
agreement on the trend. The
gray shading shows the 90%
range for the black line.
(modified from IPCC 2007)
Figure 4. Vast changes
are predicted across the
globe for just an
increase of one degree
Celsius. The predicted
changes are amplified as
global mean annual
temperature increases
(IPCC 2007). It is
important to note that
widespread coral
mortality is predicted
with temperature
increases of only 3
degrees Celsius; coral
reefs around the world
have already
experienced significant
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coral mortality between 1980 and 1999.
Shrinking Sea Ice
Arctic sea ice is shrinking and is expected to disappear during the summer melting period as early as
the middle of this century. The end of the summer melting period is the smallest extent of the Arctic
ice cap during a year and has been a point of reference that scientists use to make year to year
comparisons. This disappearance will have potentially devastating consequences for ice-dependent
species such as seals, walrus, polar bears, and some whales. IPCC (2007) models project that the
Arctic Ocean at the end of its summer-melting period may be ice free as early as 2050 (Figure 5).
However, recent observations indicate a more rapid loss of ice, perhaps signaling a quicker onset of
ecosystem effects and possibly indicating that current models are too conservative (Figure 5 and 6).
Scientists from the National Snow and Ice Data Center (NSIDC) and the National Center for
Atmospheric Research (NCAR) found that Arctic sea ice is melting faster than models have projected
(Stroeve et al. 2007). All models in the fourth assessment of the IPCC show a declining September
Arctic ice cover/extent (end of melt season) from 1953-2006 of 2.5% per decade (average across all
models). However, few if any of the models fit actual observations – 7.8% per decade. Ice loss may
accelerate if sea ice thins (Serreze et al. 2007), an alarming concern given that Nghiem et al. (2007)
determined that perennial ice that persists from year to year (that is, usually older and thicker) has
already been declining. Researchers at the National Snow and Ice Data Center think, based on
modeling simulations, that there may be a tipping point where sea ice loss will occur very quickly and
could be disappeared by 2040 (Holland et al. 2006). Scientists are concerned that the drop in ice in
2007 could indicate we may have reached this tipping point (see drop in Figure 5).
Figure 5. The observed
rate of sea ice decline has
been occurring at a much
faster rate than predicted
by even the most
‘pessimistic’ of all the
IPCC models. The
colored lines represent the
various IPCC models
predictions of sea ice
extent at its minima. The
black line is the averaged
predicted extent of sea ice
incorporating all the
models; dashed black
lines show the . . ±1
standard deviation range.
The thick red line
represents the actual
observations of the September sea ice extent, when the Arctic ice pack is at its smallest area during the year,
with the pink extension showing the precipitous drop in sea ice extent in 2007 alone. (National Snow and Ice
Data Center)
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Figure 6. The extent of
sea ice loss is difficult to
imagine, but a visual
representation gives you a
better idea from familiar
reference frames, the
continental United States
and the European
continent. The areas in red
represent the extent of sea
ice loss that occurred in
2005 (second row) relative
to its extent from 1980
(first row) and the pink
area is the additional loss
observed in 2007 (third
row). (National Snow and
Ice Data Center)
Climate change effects in Polar Regions are expected to be among the largest and most rapid of any
regions on the Earth, and will cause major physical, ecological, sociological, and economic impacts,
especially in the Arctic. Ice-associated marine algae and amphipods provide the base of a productive
food web that includes arctic cod, sea birds, ice seals, whales, polar bears, and arctic foxes. Loss of sea
ice may lead to the local loss or even extinction of those species unable to adapt fast enough to the
massive alteration of the food web that will occur with the loss of sea ice (Figure 7). Drastic ecosystem
change may affect biodiversity, economies, and indigenous lifestyles.
Figure 7. Some examples of the ocean wildlife that have adapted to the unique ecosystem provided by sea ice
in the Arctic that will be affected by loss of sea ice: ivory gulls, polar bears, bearded seals, and walrus (NOAA).
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The loss of sea ice is already projected to severely impact polar bears (USGS 2007). Population
growth rates in two subpopulations of polar bears were related to sea ice declines. It is projected that
given the current conservative estimates of sea ice loss projected by the IPCC (2007), two-thirds of the
world’s polar bear population will be lost by the middle of the 21st century.
Loss of sea ice in the Bering, Chukchi, and Beaufort Seas will impact ice-dependent ocean wildlife
(e.g., ringed seals, spotted seals, ribbon seals, bearded seals, walrus). Sea ice provides habitat for
ocean wildlife, such as ringed seals. These seals have a close association with sea ice and their
livelihood has evolved to be highly dependent upon this substrate for resting, pupping and mating,
molting, and feeding. Ringed seals excavate caves (lairs) under the snow on stable sea ice, where they
give birth to and raise their pups. The snow caves offer protection from weather and predators.
Increased temperature and loss of protective covering will increase the vulnerability of ringed seals to
predation (Kelly 2001). It is unknown whether the loss of sea ice will maintain the high levels of
productivity observed in the arctic, especially of important prey species such as arctic cod (Tynan and
DeMaster 1997). Ice seals feed on a variety of invertebrates and fishes and they in turn are major
components of polar bear diets. The loss of sea ice associated with global warming will have serious
impacts on these ice-dependent mammals (Kelly 2001, Tynan and DeMaster 1997). Sea ice provides
habitat for photosynthetic algae and nursery for invertebrates and fish and its loss could be deleterious
for these species with potential effects reverberated throughout the productive polar ecosystem. As ice
melts, a shallow mixed layer forms and is important to spring blooms and productivity that supports the
Arctic Ecosystem. Algae provide a food source for zooplankton, who in turn provide a source for
arctic cod, important in the diets of sea birds and ocean mammals. We do not know how or if these
species will be able to adapt to the level of temperature rise we are observing.
Another concern for ocean species living at the extent of the poles is how they will adapt to warming
temperatures. Species in the arctic are already pushed against a geographical limit; there will be no
colder habitats for them to move into. Range-restricted species show more-severe range constrictions
than other groups and have been the first groups in which whole species have gone extinct due to
recent climate change (Parmesan 2006).
Furthermore, with the retreat of sea ice, and seasonal ice-free waters, there is great potential for
increased disturbance in the Arctic Ocean from increased vessel traffic (increased collision with ocean
wildlife) and potential fisheries interactions (competition, bycatch) as well as offshore development
(mining and gas exploration).
Sea Level Rise
IPCC (2007) projected that global sea level will rise by 18 to 59 cm during this century, with a
negligible contribution from the Greenland and Antarctic ice sheets (Figure 8). Hansen et al. (2006,
2007) believe that with warming of two to three degrees Celsius, a concomitant rise in sea level of 6m
(600 cm) could be expected, much greater than predicted by the IPCC, with contributions from the
Greenland and Antarctic ice sheets. Such a rise in temperature is possible (within this century) if
greenhouse gas emissions, at current levels, are maintained over the next 10 years (IPCC 2007, Hansen
et al. 2006, 2007).
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Figure 8. Global mean sea level
rise (in mm) has been increasing
over time, and will increase
significantly with a continued rise in
global mean temperature. Direct
measurements are not available
before 1870, so the grey shaded area
shows the best estimates of past sea
level. The red line is the global
mean sea level measurements since
the inception of instrumentation.
The blue shading represents
projections of future sea level rise
from IPCC models. (IPCC 2007) It
is important to point out that the
maximum estimate on this figure is
far below the maximum prediction
of a 6000mm, or 6 meter, rise in sea
level that will occur if there is
significant melt contribution from
Antarctica and Greenland.
Rising sea level, caused by melting polar ice-shelves and glaciers and the expansion of warming ocean
water is already impacting the most low-lying coastal areas with the loss of coastal wetlands and
mangroves as well as increased coastal damage from flooding (IPCC 2007). In decades to come it will
continue to rise, and if unchecked could severely impact human populations, wetlands, and coastal
ocean species. Sea level rise will exacerbate inundation, storm surge, erosion and other coastal hazards
(IPCC 2007). Sea level rise will have significant impacts on those people living along the coast,
changing the landscape we know today and displacing millions of residents (e.g., Figure 9, Florida).
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Figure 9. The effects of sea level rise projected for the state of Florida. Even with a one meter rise in
sea level, widespread areas of the coast will be inundated (upper right). If Antarctica and Greenland
become major contributors to sea level rise, a change in six meters (lower right) would be expected
with widespread changes to the Florida landscape and many implications for people living along the
coast. (University of Arizona)
An increase in sea level is a threat to seals, sea lions and sea turtles that haul out onto land to rest and
for reproductive purposes (Figure 10). Low-lying sand and pebble beaches will no longer be available
for these important yearly cycle events. For example, many islands contained within the Northwest
Hawaiian Islands are low-lying and very vulnerable to increased sea level. Baker et al. (2006)
simulated potential habitat loss and determined that with a maximum sea level increase of 88cm the
loss varies from island to island, but with an increase of 129 cm from spring tides all land would be
periodically inundated They projected that endangered Hawaiian monk seals, threatened green turtles,
and endangered Laysan finch would face the greatest threats from lost habitat. The estimates used in
this study are conservative relative to the reality of current levels of ice melt observed in Greenland and
Antarctica. Given a maximal rise of 600 cm (Hansen et al. 2006, 2007) in sea level, much of this
habitat would be lost.
An increase in sea level rise will also affect other areas with low relief that are home to a diverse array
of ocean species and ecosystems (e.g., mangroves, coral reefs, shore birds, nesting turtles and
seabirds), including the Caribbean region and many low-lying islands in the Pacific.
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Figure 10. Species that have adapted to unique marine habitats at risk with sea level rise: seastars in intertidal
zone (Jim Clary/Marine Photobank), leatherback sea turtle hatchlings heading for the ocean (Jeff Pollin/Marine
Photobank), Northern elephant seal and Hawaiian monk seal that haul out onto sandy beaches (NOAA).
Ocean Acidification
The oceans play an important role in the planet’s carbon cycle by absorbing large volumes of carbon
dioxide and recycling it in various processes. Rising levels of CO2 in the atmosphere have led to
increased absorption of CO2 in the ocean where it acts as a weak acid and reduces the available level of
carbonate, required by many shell-building organisms. Increased CO2 absorption has already increased
the acidity of ocean surface waters by 30% (lowered its pH by about 0.1 units) since preindustrial times
(IPCC 2007). Based on modeling and archaeological record, oceanic absorption of anthropogenic
carbon dioxide by the end of this century will be greater than evidence from geologic record indicates
has occurred in over 300 million years. While these numbers may seem small, changes in acidity are
exponential in nature, for example pure water is neutral (7.0 units), sea water is considered basic
(around 8.0 units), and items such as cola (~ 2.5 units), wine (~4.0 units), beer (~4.5 units), and coffee
(~5.0 units) are acidic. IPCC models project that global surface pH units will decrease between 0.14
and 0.35 units over the 21st Century (IPCC 2007). These estimates by IPCC may be conservative.
Other studies have estimated that increased CO2 uptake by the oceans may increase pH by 0.3 to 0.5
units (Feely et al. 2004).
The combined effects of increased acidity (or, reduced pH) and carbonate ion concentration could have
consequences on calcifying organisms that lie at the base of the food chain such as cocolithophores or
pteropods in subarctic waters (Orr 2005, Kleypas et al. 2006, Kolbert 2006) (Figure 11). Acidification
is a severe threat to calcium carbonate shell-forming plants and animals such as marine snails and
corals that form and contribute to ocean productivity and coral reef communities. These organisms are
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likely already suffering reduced growth rates, and in time acidification, if unchecked, could make
ocean water so corrosive that the shells and skeletons of such organisms would begin to dissolve,
leading to substantial alteration of ocean ecosystems, biodiversity and productivity. Ocean
acidification reduces calcium carbonate saturation point and there have already been reductions
observed in the North Pacific Ocean (Feely et al. 2004). In some areas, this could occur by the middle
of the century. Detrimental impacts may ripple up the food chain, and affect species like whales and
seals that feed on larger crustaceans or fish species depending on small calcifying organisms (Royal
Society 2005).
Figure 11. A free-swimming planktonic pteropod, Limacina
helicina, that likely will be affected by an increase in acidity
(decrease in pH) in the ocean. They form shells made out of
aragonite (the form of calcium carbonate used by marine
organisms to form shells or skeletal structures), and are an
important food item for salmon, mackerel, herring and cod.
(NOAA)
Fragile Ecosystems – Coral Reefs
Coral reefs are among our most diverse, fragile, and endangered ecosystems. Multiple anthropogenic
(human) impacts act synergistically and imperil reefs’ continued existence. Overfishing, pollution,
global warming and ocean acidification rank among the most important of these (Bruckner et al. 2005).
Across the Caribbean, coral cover has already dropped on average by 80-90% (Gardiner et al. 2003).
Around the globe, an estimated 10-25% per cent of coral reefs have already been irretrievably lost,
another 50-70% may be gone by the middle of this century, and all could be lost by the end of the
century.
Global climate change adds the one-two punch, perhaps the knockout punch for coral reefs, of global
warming and ocean acidification on top of other human impacts. Increased sea surface temperatures
have greatly increased the frequency and severity of coral bleaching events, considered a major threat
to reefs worldwide, and may have contributed to another global threat, coral disease outbreaks, as well.
To date, because of bleaching and coral disease almost every coral community in the world has
suffered coral mortality (Marshall and Schutenberg 2006) (Figure 12).
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Figure 12. Global trend in the extent and severity of mass coral bleaching, with an increasing extent and
severity of mass mortality observed since 1998, a time period with extensive and severe coral mortality.
(Marshall and Schutenberg 2006).
Bleaching occurs when a coral polyp expels their microscopic algal symbiont, or zooxanthellae. The
zooxanthellae provides not only up to 90% of the polyps energy requirements, but also its brilliant
color. The loss of the zooxanthellae leaves the polyp devoid of color and transparent, resulting in a
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‘beached’ color (Figure 13). Projected increases in sea surface temperature this century are expected to
cause further increases in bleaching and wide-spread coral mortality (IPCC 2007) (Figure 4). Coral
reefs have already experienced widespread mortality in 1998 when an estimated 16% of corals were
damaged with bleaching and elevated ocean temperatures (Wilkinson 1998), and if the IPCC predicts
widespread mortality with a two degree increase in temperature, the future does not look hopeful for
coral reefs.
Figure 13. During prolonged exposure to increased temperatures a coral polyp will lose its algal symbiont
(zooxanthellae) and appear white in color. Corals may be able to recover if temperatures return to normal fairly
quickly; however, if increased temperatures are prolonged, the bleaching will lead to mass mortality events.
(Marshall and Shutenberg 2006).
Ocean acidification has already increased the acidity (lowered the pH) of ocean waters where corals
live beyond the levels within which they evolved over millions of years. This increased acidity has
likely lowered coral growth rates, reduced their ability to compete with other organisms, and limited
their ability to withstand predation. By the middle of this century, additional acidification will make
coral environments marginal for corals with respect to their acidity and contribute to widespread coral
and reef loss.
By the end of the century, the situation could worsen dramatically with acidity levels approaching the
point where corals could start dissolving and at which they may no longer exist as we know them.
Shifting Ranges and Distribution
The evidence that climate change is responsible for shifting ranges and distribution of species is
mounting (IPCC 2007, Parmesan 2006). Our picture of ocean ecosystems may be dramatically
transformed due to species altering their range in response to changing environmental features such as
temperature, ice cover, circulation, and salinity (Harley et al. 2006). As population sizes change and
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species shift their geographic distributions, biological communities and food webs change, with
consequences for biodiversity, ecosystem function and dependent economies. It is important to note
that many of these changes may not be simultaneous. Those species that are able to physically move
location may do so sooner than those sessile/benthic species, resulting in reorganized ecosystems with
different functional relationships Another complication arises when the timing of recurring life cycle
events (e.g., migration, mating) affect other trophic levels in the same ecosystem. Edwards and
Richardson (2004) provide evidence that the marine pelagic community is responding to climate
change, and that responses vary by community and season, leading to a mis-match between trophic
levels and functional groups.
Poleward range shifts have been well documented to date, for individual species as well as for
communities (Parmesan 2006). Distributions of exploited and nonexploited fishes in the North Sea
responded to increased temperatures, with about 2/3 of them shifting in mean latitude and/or depth over
25 years of observations. Similar documentation has been made for zooplankton in the North Sea
(Figure14). Species that shifted their distribution typically have faster life cycles and smaller body
sizes relative to non-shifting species (Perry et al. 2005). In the Bering Sea changes in the biological
community have occurred simultaneous with shifting atmospheric and hydrographic characteristics
(Grebmeier 2006). Changes in ocean and air temperatures and reductions in sea ice have coincided
with a reduction in benthic species and more favorable for pelagic communities. These changes in
prey base have negatively affected higher trophic species such as seabirds and ocean wildlife
populations, such as Steller sea lions.
Figure 14. Changes in the mean number of zooplankton species in the North Atlantic between 1960 to 1975
and 1996 to 1999. The number of temperate species increased and the diversity of colder-temperate, sub-Arctic
species and Arctic species decreased in the north Atlantic. The scale (0 to 1) indicates the mean number of
species in total assemblages of zooplankton. From Beaugrand et al. 2002b. (IPCC 2007)
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Human Impacts
Coastal communities and ocean-based societies and economies will suffer substantial losses in coming
decades as the effects of global warming on the oceans continue, causing extensive flooding, damaging
and destroying coastal natural and built environments, reducing or shifting ocean productivity with
impacts on fisheries and aquaculture, and compromising and eliminating, in some cases, historic
human use of coasts and the ocean.
Rising sea level is currently affecting low-lying nations, such as the Pacific island of Tuvalu, where
tide water floods homes and the streets. Hunter (2002) determined that sea level rise has been 1.2 mm
per year, and the country is currently examining relocation options along with the fear of the loss of
their culture (Patel 2006).
On the other side of the globe, small arctic villages along the Chukchi and Beaufort Seas share close
cultural ties to the ocean, too, are facing possibility of relocation. Decreased arctic sea ice along with a
loss of permafrost that provided rigidity and support to coastlines has impacted coastal communities
with increased erosion from late winter storms that ordinarily occur once the sea ice has set in (Figure
15). Other concerns associated with climate change that also stress these coastal environments include
the loss of permafrost, sea level rise, and the increased frequency and intensity of storms. The National
Park Service has examined coastal erosion in two northwest national parks and have determined that
since 1987 shoreline has been lost at a rate of 1 to 10 meters per year (or 3-30 feet) (Jordan et al. in
press, Manley et al. in press). In another study, along the Beaufort Sea, the USGS examined 50 years
of coastal region, from 1955 to 1985 an average rate of land loss of 0.5 km2/year was lost; whereas
from 1985 to 2005 an average rate of land loss of 1.1 km2/year was lost (Mars and Houseknect 2007).
Figure 15. Coastal erosion at Shishmaref, Alaska (an Inupiat village in the Chukchi Sea, just north of the
Bering Strait) during a two-hour period. Note the loss of land immediately to the left of the oil drum,
highlighted by the red arrow. (National Snow and Ice Data Center, Serreze 2007)
Human health is predicted to decline due to increased risk of mortality and injury because of climate
change related causes (IPCC 2007) (Figure 16). Some of the increased deaths may be due to infectious
diseases because of heavy precipitation events; food and water shortages and water and food borne
diseases because of areas affected by drought; death and food and water borne diseases because of
intense tropical cyclone activity; and by drowning in floods because of increased incidence of extreme
high seas. Many of the effects of climate change on society will be worst for those people residing in
economically poorer nations with limited adaptive capacity (IPCC 2007).
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Figure 16. Many impacts on human health will be negative in nature. Direction and magnitude of change of
health impacts from climate change (IPCC 2007).
Conservation Implications of Climate Change
All ocean species already face a barrage of anthropogenic-based stressors. Non-climate stresses can
increase vulnerability of ocean species to climate change by reducing resilience and reducing their
adaptive capacity to react to the physical effects of climate change (IPCC 2007). Climate change may
exacerbate current stressors that these species deal with, and the scientific community at-large is
concerned that the effects of climate change acting together with existing threats, will accelerate the
rate at which we lose biodiversity (Parmesan and Galbraith 2004). A resilience-based approach (of
minimizing other anthropogenic stressors) to management of ocean ecosystems is key to ensuring that
ocean species such as coral reefs or marine mammals may better deal with habitat changes associated
with climate change.
For example, in the North Pacific, Steller sea lion abundance and distribution is greatly affected by a
number of physical and biological oceanographic parameters as well as climatological conditions
(Trites et al. 2007). These are factors that may be difficult to influence on any real-time basis. Other
stressors on the species, such as overfishing, entanglement in fishing gear, intentional shootings, and
pollutants, are more readily managed at the local level than factors associated with climate change. In
addition, these factors have been the subject of much research and monitoring, and we have a better
understanding of how management actions might benefit this species. Addressing anthropogenic
stressors as a first line of defense will increase the resiliency of marine mammal species to short and
long-term impacts of climate change.
Protecting important habitat is also critical to combating potential effects of climate change (Harley et
al. 2006). Hoyt (2005) argues that habitat of cetaceans is best protected through ecosystem-based
management approaches using a carefully selected network of marine reserves. In some cases, reserves
have been established specifically for the protection of marine mammals (see Hoyt 2005 for a complete
list). In other cases, marine reserves have been designated for protection of important fish stocks
(CDFG 2007). Protected no-take areas are vital tools for the conservation and protection of ecosystem
resilience of coral reefs (Mumby et al. 2007, Hughes et al. 2007).
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Species that suffer reductions in range and habitat size are at greater risk of extinction. Species with
slow generation time might not have enough time for an adaptive response to rapid change in climate.
Species with low genetic diversity or species that reproduce with clones may also be more susceptible
to extinction. Given the uncertainty about the effects of climate change on ocean species,
incorporating an adaptive approach to management that provides flexibility in how species and their
habitats are managed is key (Elliott and Simmonds 2007, Hollowed et al. 2007, Harley et al. 2006,
Learmonth et al. 2006,).
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