STATEMENT OF

#### **DR. SUSAN D. HASELTINE**

ASSOCIATE DIRECTOR FOR BIOLOGY

U.S. GEOLOGICAL SURVEY

U.S. DEPARTMENT OF THE INTERIOR

BEFORE THE COMMITTEE ON SCIENCE AND TECHNOLOGY

SUBCOMMITTEE ON INVESTIGATIONS AND OVERSIGHT

U.S. HOUSE OF REPRESENTATIVES

OCTOBER 17, 2007

Mr. Chairman and Members of the Subcommittee, thank you for the
opportunity to participate in today's hearing to discuss emerging
insights into the present and potential influences of climate
variability and change on resources of interest to the American people.
My name is Dr. Susan D. Haseltine, and I am the Associate Director for
biology at the U.S. Geological Survey (USGS).

Global climate change is one of the most complex and formidable
environmental challenges facing society today. While climate change is a
natural, continuous Earth process, changes to the Earth's climate are
related to human activities as well. Whether the causes are natural or
from human influence, our focus is on understanding the impacts of
climate change and the potential adaptive strategies for managing
natural resources and ecosystems in the face of these changes.

Today, one need only turn to the Far North to witness the emerging
signature of climate change. In Arctic and subarctic regions, the
shrinking extent of and structural changes in sea ice and permafrost are
a strong and visible signal of contemporary change in the Earth's
climate system. Sea ice controls its associated ecological systems: From
oceanographic patterns through the food chain to ice seals and polar
bears, the Arctic marine world is tied to the dynamics of sea ice. I
will focus my remarks on the realm of sea ice and recent publications by
the USGS on this environment and its top predator, the polar bear. It
should be recognized that this important work is part of a broad body of
research carried out by other Federal agencies and nations around the
Arctic.

Data from the observed record document a recent history of change in
Arctic sea ice. Observations from the available satellite record
(1979--2007) show a decline of 10 percent per decade in the minimum
annual Arctic sea ice extent (end of summer melt season). That decline
is punctuated by this year's (2007) melt season, which reduced the
minimum ice cover in the Arctic to just over 4 million square
kilometers---as compared to the 7-8 million square kilometers observed
at the beginning of the satellite record (1979-1980). The 2007 melt
season thus reflects a roughly 40 percent reduction in ice extent from
the 1979--2000 average. Even more significant is the degree to which the
year 2007 surpassed the previous sea ice loss record of 2005---by about
one million square kilometers.

Owing to the influential role that sea ice plays in Earth's climate
system, numerous institutions and agencies worldwide (including the
USGS) are conducting research to better understand the mechanisms and
trajectory of sea ice change. The USGS is an active collaborator in this
arena. Complementing the extensive amount of research supported by the
National Science Foundation, NASA, NOAA and others, the USGS is helping
to define an emerging understanding of the changes in ice age structure
and the relationships of those trends to atmospheric circulation
patterns, thermal forcing, and other controlling mechanisms. While
rising Arctic air temperatures have certainly contributed to the loss of
sea ice, several other factors have interacted to accelerate the loss.
Changes in prevailing wind patterns (Maslanik et al. 2007) have caused
much of the older and thicker sea ice to drift out of the Arctic Ocean
(Rigor and Wallace 2004; Belchansky et al. 2005), leaving behind a
younger and thinner ice pack that is more vulnerable to the summer melt
season. Concurrently, warmer ocean water has been entering the Arctic
from both the Atlantic (Polyakov et al. 2007) and Pacific (Woodgate et
al. 2006). A warmer Arctic Ocean further reduces the air-water
temperature gradient, which suppresses winter ice growth (thickening)
and renders it more susceptible to summer melt. And finally, onset of
the Arctic melt season has been getting earlier (Belchansky et al. 2004;
Stroeve et al. 2006). Earlier springs trigger an earlier start to an
important positive feedback loop that begins when the bright surface of
the ice darkens from the presence of melt ponds and open water, the
darker surfaces warm faster because they absorb more solar radiation,
and the warmth promotes more melt---and so on. To what degree natural
climate variability has exacerbated the recent loss of sea ice is not
well understood. However, there is growing scientific concern that the
synergism of recent events, regardless of their origin, may have already
pushed the Arctic past a threshold of cascading change (Lindsay and
Zhang 2005; Serreze and Francis 2006).

The USGS is well poised to address the implications of ecological change
in the Arctic by integrating its geophysical and biological expertise.
Foremost among USGS biological studies in the Arctic is a long-term
program of polar bear research. Owing to both the study's three-decade
history and its longstanding collaboration with countries within the
circumpolar distribution of polar bears, the USGS has accumulated a
robust baseline of data crucial for assessment of population status in
long-lived species such as the polar bear, for defining essential
habitats, and for making projections of population status into the
future. Nine recently released USGS reports build on this history of
research and culminate in a new rangewide forecast of polar bear status
under various projections of future climate change (Amstrup et al. 2007;
Bergen et al. 2007; DeWeaver 2007; Durner et al. 2007; Hunter et al.
2007; Obbard et al. 2007; Regehr et al. 2007a; Rode et al. 2007;
Stirling et al. 2007).

Polar bears occur throughout portions of the Northern Hemisphere where
the sea is ice-covered for all or much of the year and essentially
derive their sustenance predominantly from ice seals such as ringed
seals. The dependence of polar bears on hunting at the ice surface
raises concern about the implications of sea ice loss. In the southern
parts of the polar bear range, such as Hudson Bay, the sea ice melts
entirely each summer and bears fast until the ice refreezes in autumn.
However, warming temperatures have established a trend of earlier sea
ice break-up, leaving the bears stranded on land and deprived of food
for longer periods of time (Stirling and Parkinson 2006). Recent data
published by USGS and Canadian scientists document lower survival rates
among young and sub-adult bears and establish scientific linkages
between less ice cover, reduced survival, and population decline (Regehr
et al. 2007b).

Similar to the early-warning signs seen in Western Hudson Bay, declines
in body condition and survival are now documented for polar bears in
Southern Hudson Bay and the Southern Beaufort Sea. These and other signs
of stressed polar bear populations, together with the observed and
forecasted declines in sea ice, prompted the USGS to assemble a team of
polar bear, sea ice, and modeling experts aimed at reducing the
uncertainties of observed and forecasted polar bear population status
worldwide.

Because of the poor fossil record, we do not know how the forecasted
distribution of bears compares to bear distribution at other times in
the past when ice extent may have been restricted similarly to the
models used for our forecasting.

The USGS assessed the pattern of observed changes in polar bear--sea ice
habitat over the last two decades and forecasted the range of likely
future habitat conditions out to the end of the centuryUsing long-term
satellite tracking data from polar bear populations inhabiting the polar
basin (Arctic Ocean), the USGS constructed habitat selection models
using data collected during 1985-1995, before the sea ice changes had
become pronounced. The resulting models demonstrated a strong preference
for sea ice habitats that were near the periphery of the ice pack and
over the shallow waters of the continental shelf. USGS habitat models
for the 1996-2006 period found preferred habitats have already declined,
especially in spring and summer with greatest losses in the Southern
Beaufort, Chukchi, Barents, and Greenland seas (Durner et al. 2007).

The USGS then projected the range of likely future polar bear habitat
conditions employing ten General Circulation Models (GCM) from the
Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment
Report. These models were selected on the basis of their ability to
reasonably simulate the amount of observed sea ice cover in the Northern
Hemisphere during the 20th century. It should be noted that the USGS
used GCM projections derived entirely from the IPCC SRES-A1B greenhouse
gas emissions scenario, which is also called the "business as usual" or
"middle of the road" scenario, to develop sea ice projections.
Preliminary USGS analyses of other emission scenarios (as corroborated
in the IPCC Fourth Assessment Report) indicate that scenarios with less
atmospheric carbon dioxide loading do not make a substantive change in
polar bear outcomes through mid-century, but do result in less depletion
of sea ice and thus polar bear habitat at the end of the century.

Projections from the 21st century-based models exacerbated the already
observed habitat losses, and added losses throughout all regions
bordering Russia. Annual habitat loss for the full basin is projected at
more than 35 percent by the end of the century, with a summer loss of
nearly 80 percent for the Alaska-Eurasia portions of the Basin. In
contrast, polar bear habitats were projected to be relatively stable
during the 21st century in the high-latitude regions along the
northwestern Canadian Archipelago and northern Greenland. These results
are consistent with the general observation that most GCMs project
modest ice declines in winter but strong declines in summer, resulting
in either ice-free summers or remnant summer ice at the northernmost
latitudes of North America.

To forecast the status of polar bear populations worldwide during the
21st century requires not only information on likely future habitat
condition (Durner et al. 2007) but also projections of population status
based on present vital rates (Hunter et al. 2007). The USGS then
developed a Bayesian network (BN) model structured around population
stressors that could affect the factors considered in Endangered Species
Act decisions (Amstrup et al., 2007). The BN model combined empirical
data, interpretations of data, and professional knowledge into a
probabilistic framework. The BN model incorporated information about
annual and seasonal sea ice trends on populations as well as potential
effects of other population stressors such as harvest, disease,
predation, and effects of increasing human activity in the north due to
ice retreat. Sensitivity analyses of the final model indicates that sea
ice habitat loss is the over-arching stressor responsible for model
outcomes. Model results show that by mid-century, polar bear populations
will likely be extirpated, or eliminated, from their southernmost range
in southeastern Canada, as well as from regions of the polar basin
bordering Alaska, Russia, and Europe. By late-century, populations in
East Greenland and the Northern Beaufort Sea also have a high
probability of extirpation. Model projections indicate a high likelihood
of extirpation from regions of the Arctic that presently support
two-thirds of the worldwide population of polar bears. These models,
however, also predict a strong likelihood of remnant populations
surviving in the high Arctic, which may provide a source of animals to
reestablish former ranges if the Arctic's sea ice environment were to be
restored by an ultimate slowing and reversal of global warming.

The USGS recognizes that the momentum of atmospheric greenhouse gas
loading will challenge us with climate-related issues for at least the
next 30--50 years. As such, we anticipate that the traditional
approaches to natural resource conservation, public land management, and
civil infrastructure planning may require accommodating and adapting to
ecosystem change. The USGS conducts scientific research to understand
the likely consequences of climate change, especially by studying how
climate has changed in the past, then using the past to forecast
responses to shifting climate conditions in the future, distinguishing
between natural and human-influenced changes, and recognizing ecological
and physical responses to changes in climate. These strengths allow the
USGS to play a critical role in conducting climate change science across
the Nation. A better understanding of sea ice must be combined with an
understanding of ecological responses and adaptation. We believe that
coupled physical-biological forecasting approaches, as presented in
recent USGS polar bear reports, will better prepare decision makers as
they address climate adaptation. Such forecasting will require continued
long-term monitoring, focused studies of process, and the application of
new and emerging modeling approaches implemented through collaborative
efforts among Federal, academic and other partners.

Thank you for the opportunity to present this testimony.  I am pleased
to answer any questions you and other Members of the Committee might
have.

[References:]{.underline}

Amstrup, S. C., B. Marcot, and D. C. Douglas. 2007. Forecasting the
range-wide status of polar bears at selected times in the 21st century.
USGS Report to USFWS.

Belchansky, G. I., D. C. Douglas, and N. G. Platonov. 2004. Duration of
the Arctic sea ice melt season: regional and interannual variability,
1979--2001. J. Climate, 17:67--80.

Belchansky, G. I., D. C. Douglas, and N. G. Platonov. 2005. Spatial and
temporal variations in the age structure of Arctic sea ice. Geophys.
Res. Lett., 32, L18504, doi:10.1029/2005GL023976.

Bergen, S., G. M. Durner, D. C. Douglas, and S. C. Amstrup. 2007.
Predicting movements of female polar bears between summer sea ice
foraging habitats and terrestrial denning habitats of Alaska in the 21st
century: Proposed methodology and pilot assessment. USGS Report to
USFWS.

DeWeaver, E. 2007. Uncertainty in climate model projections of arctic
sea ice decline. USGS Report to USFWS.

Durner, G. M., D. C. Douglas, R. M. Nielson, S. C. Amstrup, and T. L.
McDonald. 2007. Predicting the future distribution of polar bears in the
pelagic Arctic from resource selection functions applied to 21st century
general circulation model projections of sea ice. USGS Report to USFWS.

Hunter, C. M., H. Caswell, M. C. Runge, E. V. Regehr, S. C. Amstrup, and
I. Stirling. 2007. Polar bear demography in the Southern Beaufort Sea in
relation to sea ice. USGS Report to USFWS.

Lindsay, R. W., and J. Zhang. 2005. The thinning of arctic sea ice,
1988--2003: Have we passed a tipping point? J. Climate, 18:4879--4894.

Maslanik, J. A., S. Drobot, C. Fowler, W. Emery, and R. Barry. 2007. On
the Arctic climate paradox and the continuing role of atmospheric
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Obbard, T. L. McDonald, E. J. Howe, E. V. Regehr, and E. S. Richardson.
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Polyakov, I., and 19 others. 2007. Observational program tracks Arctic
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Regehr, E. V., C. M. Hunter, H. Caswell, S. C. Amstrup, and I. Stirling.
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Regehr, E. V., N. J. Lunn, I. Stirling, and S. C. Amstrup. 2007b in
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Rode, K. D., S. C. Amstrup, and E. V. Regehr. 2007. Polar bears in the
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