[STATEMENT OF]{.smallcaps}

[JAYNE BELNAP, RESEARCH ECOLOGIST]{.smallcaps}

[U.S. GEOLOGICAL SURVEY]{.smallcaps}

[U.S. DEPARTMENT OF THE INTERIOR]{.smallcaps}

[BEFORE THE]{.smallcaps}

[SENATE COMMITTEE ENERGY AND NATURAL RESOURCES]{.smallcaps}

[SUBCOMMITTEE ON PUBLIC LANDS AND FORESTS]{.smallcaps}

[HEARING ON THE MAJOR ENVIRONMENTAL THREATS TO]{.smallcaps}

[THE GREAT BASIN IN THE 21^ST^ CENTURY]{.smallcaps}

[OCTOBER 11, 2007]{.smallcaps}

Mr. Chairman and Members of the Subcommittee, thank you for the
opportunity to appear here today to discuss how climate change models
can help us better understand the interaction between climate change and
environmental threats in the Great Basin/Colorado Plateau region.

Climate change is perhaps the most complex and multi-faceted challenge
facing public land managers. Climate change affects biota, water,
ecosystems, cultures, and economies. Although 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 influences, the U.S. Geological Survey (USGS) climate change
focus is on understanding its impacts and the potential adaptive
strategies for managing natural resources and ecosystems in the face of
these changes.

**[Climate Change Modeling]{.underline}**

The most recent generation of global climate models are called
Atmospheric-Ocean Global Circulation Models (AOGCM) because the
predictions from these models are based on data from the atmosphere,
oceans, and land masses. Atmospheric data in the models describe
transfers of heat, radiation, and water vapor, and the processes of
cloud development and precipitation. Oceanic factors include sea surface
temperatures, sea ice, and ocean currents. Land factors include
vegetative cover, soil types, water storage and the type of water
delivery (*i.e.*, rain versus snow). As the name implies, AOGCM combines
these factors to create global climate models.

There are many issues that create uncertainty in these models. The most
problematic concern how clouds, sea ice cover, and atmospheric
greenhouse gas concentrations affect climate. Clouds affect climate in
many ways, including increasing or decreasing radiation, creating
precipitation, and affecting small-scale circulation patterns. To
illustrate the problem, clouds cover approximately 60 percent of the
Earth's surface and are responsible for up to two thirds of Earth's
albedo (reflectance of light from the surface -- which is about 30
percent). A decrease in albedo by only 1 percent can increase
temperatures by about 1°C. Secondly, the future extent of sea ice and
snow fields, which have a large influence on the outcome of the models,
is another unknown. As the concentrations of greenhouse gases rise and
warm the Earth, snow and ice begin to melt. As the underlying ground or
water is darker than the snow and ice, they absorb more heat from the
Sun, causing more melting, which results in additional warming. This
creates a feedback loop known as the 'ice-albedo feedback'. Lastly, the
level of emissions (carbon dioxide and other greenhouse gases) that can
be expected in the future is unknown. Detecting, understanding and
accurately quantifying such feedbacks and emissions is extremely
difficult, but the valuation of these factors can greatly alter climate
predictions.

There are issues associated with downscaling of the AOGCM projections as
well. Whereas we are fairly confident in global-scale drivers of
climate, the effect of local factors are much less certain. There are
two main approaches to downscaling. The first approach constructs an
empirical relationship between a local factor (*e.g.*, stream flow) and
large scale atmospheric circulation model prediction of that factor. The
second approach, dynamical downscaling, basically uses a weather
prediction model to downscale AOGCM output to much higher resolutions.
Both methods have their advantages and disadvantages. Empirical
downscaling requires a long record of high quality data in order to
build the required empirical relationships. For many parts of the United
States, such records are lacking. For example, there are very few
long-term climate station records in the Great Basin/Colorado Plateau
region that can be used to create or verify downscaled models. In
addition, the paucity of climate stations means that climate information
for a specific location can only be modeled (that is, data from a few
stations are extrapolated over a larger area that has similar elevation,
topography, etc.). Thus, data for the model is often coming from another
model, increasing the risk of error.

The primary disadvantage of dynamical downscaling is the high
computational cost. Both methods will give erroneous climate projections
if the large-scale circulation provided by the AOGCMs is incorrect, as
they provide the boundary conditions for the heat, water vapor, and
pressure fields. As physical equations are then used to calculate what
these fields are in higher resolution, any error in the large scale
fields is propagated throughout the downscaled models.

**[Use of Models in Understanding Future Conditions]{.underline}**

It is not valid simply to extrapolate the observed past changes in
climate change forward into the future. However, the demonstrated
success of current climate models in simulating the global pattern of
observed 20^th^ century changes means that those models are credible,
though far from perfect, tools for looking into the future. As discussed
in more detail below, given the most realistic assumptions about future
atmospheric carbon dioxide concentrations and other drivers of climate
change, these models project a long-term drying trend in the Southwest,
including the Great Basin. The drying trend in the Southwest implies an
increasing probability of occurrence of Southwestern drought.

These projections are, at best, a general outline of climate change for
the real future. I note, however, that there is much room for
improvement. For example:

-   Climate models typically represent conditions over very large areas.
    Such an approach has been adequate to assess global warming.
    However, climate varies geographically on a much finer scale,
    especially in mountainous regions. Therefore, to assess practical
    impacts on water and to design, plan, and implement needed
    adaptations, resource managers and policymakers need information on
    a much finer spatial scale, more like that of a county. To deliver
    this, much-higher-resolution climate models are needed.

-   The Nation has no comprehensive network for the monitoring of
    climate change. The available measurements, assembled from stations
    established for other purposes, such as stream gauges, have proven
    critical for the progress that has been made in detecting global
    change. However, keeping higher-resolution models accurate and
    tracking ongoing changes related to climate change impacts will
    require higher-resolution measurements.

-   Current climate models do not capture the effects of development,
    land use, and land-cover change on climate. This has not been
    identified as a crucial impediment for global analyses, but it
    likely matters at the finer spatial scale of most resource
    management decision-making.

-   A change in climate causes a change in water demand, e.g., for
    irrigation and for natural ecosystems. Our understanding of this
    relation between climate and water demand needs improvement if
    models are to be more effective in predicting the effects of climate
    change on future water needs.

-   To make best use of available information in a changing climate,
    resource managers will need to employ a wider variety of
    science-based decision support tools than those that have sufficed
    in the past. These new tools must recognize that climate will change
    during the lifetime of an operational project and that estimates of
    the changing climate are uncertain. This will require a sea change
    in the field of resource management. Such a change will not be
    accomplished without a concerted effort by government, academia, and
    professional societies.

**[Modeling and Research Findings]{.underline}**

The averaging of 21 climate models predicts that temperatures will
increase by up to 6^o^ C (11^o^ F) in the Great Basin/Colorado Plateau
region during the next century (Christensen et al., 2007). This is a
large increase, and thus, it is likely to have profound effects on water
resources and the living systems that depend on those resources.
Atmospheric carbon dioxide and nitrogen levels are also likely to
increase. There is much more uncertainty in predicting future
precipitation than temperature. Precipitation predictions vary widely,
depending on how the models are constructed. The Intergovernmental Panel
on Climate Change averaged model predicts 5-10 percent increase in
winter precipitation, 0-15 percent decline in summer precipitation, and
0-5 percent decline in annual precipitation (Christensen et al., 2007).

In addition, a review of these models shows that extreme events (*e.g.*,
drought, wet years, floods, high winds) will increase. These extreme
events will cause significant challenges to the biological components of
the Earth system in terms of their ability to adapt or mitigate to other
areas as a result of abruptly-changing climate (Christensen et al.,
2007).

Land use activities (*e.g.*, recreation, clearing for housing, grazing,
cropland, military activities) are also increasing rapidly in this
region and will further exacerbate the effects of climate change on
biological resources. These activities enhance the invasion of exotic
plants, reduce or remove vegetative cover, and destroy physical and
biological soil crusts, leaving soils unprotected, reducing forage and
habitat, and increasing the reflectance, or albedo, of the soil surface
(Foley et al., 2005; Notaro et al., 2006).

**Invasive Species**

With climate change and land use invasive plants, especially exotic
annual grasses, will likely increase. Soil surface disturbance, elevated
carbon dioxide levels, the deposition of atmospheric nitrogen, and
increased fire will all contribute to a likely increase in exotic annual
grasses such as cheatgrass (D'Antonio and Vitousek, 1992; Brooks et al.,
2004). In an area such as the Great Basin/Colorado Plateau region, where
exotic annual grasses have been replacing native perennial plant
communities, this could have severe consequences, resulting in years
where such landscapes will have little or no forage and habitat for
wildlife and livestock, resulting in a severe loss of biodiversity.
During this time, soils will also be highly vulnerable to erosion. In
addition, annual grasses alter soil biota, decomposition rates, and
nutrient cycling rates, resulting in lower soil fertility.

**Wildland Fire**

Fire frequency and severity will also increase with the invasion of
annual plants and future extreme wet/dry conditions. Re-burning of areas
facilitates further annual plant invasion, which will lead to increased
fire frequency (Brooks et al., 2004). Because most desert shrubs grow
slowly and require extended periods without fire to re-establish, more
frequent fire is particularly destructive in shrub-dominated desert
systems such as those found in the Great Basin/Colorado Plateau region.
With the loss of perennial vegetation, important microclimates are lost,
including those that enhance the germination and establishment of native
plants and habitat for native animals. Fire can also create hydrophobic
soils that, when combined with loss of vegetation cover, allow for
increase soil erosion, and can deplete the nutrient and carbon stocks in
soils. Biota living at, or just beneath, the soil surface are often
killed, slowing decomposition cycles and reducing soil nutrient
availability.

**Soil Moisture**

As temperatures rise, soil moisture will decrease. One study has shown
that, by 2050, even if there is no decrease in precipitation, increasing
temperatures alone will result in average soil moisture conditions being
lower than those experienced during any of the mega-droughts of this
century (Dust Bowl years of the 1930s; drought years 1953-1956 and
1999-2004; Andreadis and Lettenmaier, 2006). This will result in reduced
plant cover and biomass, and thus, less forage and habitat for livestock
and wildlife. Insect outbreaks are also often associated with lower soil
moisture, as the resistance of vegetation to infestation is reduced as a
result of this stress. The combination of dry soils and insect
infestation have been known to kill thousands of square miles of
vegetation (*e.g.*, the 2002-2003 Ips beetle infection/infestation of
Pinyon Pine in the Southwest United States), leaving the area highly
susceptible to fire and subsequent invasion by weeds (Breshears et al.,
2005).

Observations during dry periods of above average temperature have also
shown that shallowly rooted plants, such as perennial grasses and
cactus, will be highly vulnerable to future dry and hot conditions
(Ehleringer et al. 1999; Breshears et al. 2005). Many animals at the
base of the food chain (*e.g.*, mice, rabbits) depend on grass and
cactus for food and shelter; thus, a reduction in these species is
expected to reverberate upward, resulting in the loss of predators such
as raptors, mountain lions, and bears. Grass is also the main food for
cattle and elk. Soil lichens, which add stability, carbon, and nitrogen
to soils, also die with increased temperatures. Their loss will further
contribute to a reduction in soil stability and fertility (Belnap et
al., 2006).

Research by USGS and colleagues shows that increased warming could
decrease runoff by up to 30 percent in many streams and rivers in the
Great Basin/Colorado Plateau region (Milly et al., 2005). This includes
water in the Colorado River, which currently supplies the needs of 25
million people in seven U.S. states, two Mexican states, and 34 Native
American tribes (Pulwarty et al. 2005). As population grows, the demand
for water will increase at the same time that water availability is
decreasing due to climatic conditions (and soil erosion, see below).
Small springs and streams may dry up earlier in the season, or
completely, placing plants, animals, and humans that depend on surface
water at risk.

**Soil Erosion**

Research by USGS and others shows that desert soils are mostly stable
until disturbed (Marticorena et al., 1997; Belnap, 2003). However, the
interaction of lower soil moisture, fire, exotic plant invasions, and
surface-disturbing activities will reduce the cover of natural soil
stabilizers (plants, physical and biological soil crusts, rocks) and
result in greater soil erosion. Restabilization of these soils often
depends on heavy precipitation events; thus soils will continue to erode
during continued drought. As erosion differentially removes the fine
particles in soils to which nutrients are attached and which increase
water-holding capacity of the soil, the remaining soils are less fertile
and dry more quickly. This will result in less plant biomass and thus
less forage and habitat for wildlife and livestock. In addition, reduced
soil fertility will likely result in a reduction in the nutritive
quality of the plant tissue (Marschner, 1995). Thus, livestock and
wildlife will need to eat more to meet their nutritional requirements.

Soils eroded by water increase the sediment load in streams and,
ultimately, large rivers. These sediments are often heavily laden with
salts and heavy metals, contributing to water-quality problems
downstream. Soil deposition into small springs and streams can be
especially problematic, as the amount of water present is so low the
resource can be completely lost.

**Dust Storms**

One largely overlooked issue regarding soil erosion by wind is that it
can produce dust storms that can have profound and lasting effects. Dust
obscures visibility on highways and thus endangers travelers. If
inhaled, the fine particles found in dust can cause asthma and other
respiratory disease. Dust can carry Valley Fever, which can be fatal
(Kirkland and Fierer, 1996). Dust storms can cause large economic losses
through lost work time and ruined machinery. Blowing sediment can bury
plants and eliminate habitat and forage. Dust also affects water storage
and delivery. When dark-colored dust is deposited on the snowpack of
downwind mountains and absorbs solar radiation, the underlying snowpack
melts 30 days or more earlier than normal (Painter et al., 2006).
Earlier melting reduces water storage in the snowpack, thereby reducing
the amount of water that is available in streams and rivers during late
summer. A faster melting rate may also increase spring flooding,
reducing the opportunity to store water in those downstream reservoirs
(Parker, 2000).

**Increased Albedos**

The loss of vegetation turns the Earth's surface from a dark color to a
light color. Thus, the energy from the sunlight hitting a lightened
surface is reflected upwards, rather than being absorbed by dark
vegetative surface. In addition, the surface is smoothed and moisture
evaporated from plants is lacking. The resultant rising hot and dry air
reduces cloud formation, thus reducing subsequent precipitation. The
result can be dramatic. Areas with reduced vegetative cover receive less
precipitation than adjacent land covered by vegetation (Charney et al.,
1975). Therefore, as land use, drought, fire, or a combination of these
factors results in reduced vegetative cover, we can expect a reduction
in precipitation as well (Foley et al., 2005; Notaro et al., 2006). This
often creates a feedback loop, where drought reduces vegetative cover
which increases albedo; this increase, in turn, increases the severity
of the drought, which further reduces vegetative cover. This problem is
especially severe where native perennial plants have been replaced by
annual grasses. Under drought conditions, soils in these areas often
completely lack vegetative cover, and thus albedos are greatly
increased.

**Plant Re-establishment**

Because plant recovery depends on soil moisture availability, lower soil
moisture will slow or prevent the recovery of plants and soils from fire
or surface-disturbing activities. The presence of invasive annual
grasses will often prevent the re-establishment of native vegetation by
facilitating frequent fires, killing the native plants (Brooks et al.,
2004). Almost all the research done on restoring drylands has occurred
during the past 30 years, which was a relatively wet period. Thus, many
of the restoration techniques that have been developed may not work
under anticipated future dry conditions. Additional research will be
needed to determine restoration techniques under dry conditions.

Natural and human-caused disturbances have interacted over the past
several decades to change rangelands and ecosystems across as much as
one half of the Great Basin's one hundred million acres (McIver et al.,
2004). Protracted drought coupled with invasive species, altered fire
regimes, grazing, human settlement and recreation, and energy
exploration and development have yielded suites of vegetation that often
cannot support wildlife species. Increasing annual temperature and
decreasing precipitation regimes have exacerbated these ecological
changes, and climate change will continue to interact with plant and
animal dynamics on dry lands.

# [Conclusion]{.underline}

To better understand the interaction between climate change and these
environmental threats, and to provide the science needed by resource
managers and decision makers, the USGS is working to:

-   understand how climate change, and the interaction among climate,
    land use, invasive plants, and fire, will impact ecosystem
    processes, soil stability and fertility, plants, wildlife, and
    humans at the local and regional scale.; document past climate, land
    use, land cover, and disturbance regimes (e.g., fire, extreme
    climate events); expand existing, long-term monitoring of climate,
    air, and water quality (including wind and water borne sediments),
    soils, ecosystem processes, vegetation, animals, and land use/land
    cover; and simulate future conditions with experimental research
    techniques and modeling;

-   document how the interactions between hydrology, climate, land use,
    and vegetation affect soil movement; identify and map soils
    vulnerable to invasion and erosion, and identify where eroded soils
    are deposited; research ways to alter the type, timing, and
    intensity of land use to reduce soil movement; measure the effects
    of dust on water storage (in soils, ground water, aquifers, and
    snowpack), delivery (timing, intensity, and duration), and quality
    (salinity, heavy metals, sediment load); document impacts of altered
    hydrologic cycles on terrestrial and aquatic resources; expand
    current water-quantity and water-quality monitoring at different
    scales within the watershed, expand current aquatic and terrestrial
    resource monitoring, and determine the sources and sinks for
    mobilized sediment;

-   research new restoration techniques and test old techniques under
    future climate conditions in collaboration with our colleagues at
    land management agencies such at the Bureau of Land Management;
    research ways to restore ecosystem processes, such as decomposition
    and nitrogen cycling; test old restoration techniques under future
    conditions by using manipulative research;

-   model future climate change at the regional and local scale and use
    the understanding of the interactions discussed above to forecast
    future conditions in relation to changing climate, land use,
    disturbance, and land cover; and

-   effectively communicate these findings to policy makers, land
    managers, scientists, and the public.

Mr. Chairman, thank you for this opportunity to present testimony. I
would be pleased to respond any questions that you or other Members of
the Subcommittee may have on this topic.

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