Present-Day Environments and Climate Change - Mountains and Plains: The Ecology of Wyoming Landscapes - page 38

cies composition, insect outbreaks accelerate nutrient
cycling and may affect forest flammability (see chapter
11). notably, these insects are native species and have
coexisted with their hosts for millennia.
overall, an environmental analysis for any area must
consider the interaction of many factors that change
either gradually or abruptly across landscapes and over
time. no two areas have exactly the same environment;
generalizations must be made with caution. this com-
plexity makes the environment difficult to conceptual-
ize, but it is often helpful to focus on a few variables.
Key variables in the region include soil characteristics
(especially infiltration rates, water-holding capacity,
and salinity of the soil), water availability in the soil,
and seasonal and elevational temperature differences.
Periodic disturbances by fire, wind, burrowing animals,
and a few insect species further modify an already
diverse landscape mosaic. Regionally, different climates
have caused the formation of grasslands, shrublands,
forests, and tundra. Locally, the nature of the vegeta-
tion is dependent on soil characteristics; topographic
differences; snow drifting; and such disturbances as
fire, flooding, and windstorms.

of an area over a period of several decades or more. they
point out that unusually cold days will occur during the
warmest month on record and that above-average pre-
cipitation can fall in the middle of a 10-year drought.
climatologists also emphasize that climate trends
will not be the same everywhere. even with an over-
all trend of warming on earth as a whole, some areas
will be cooler or wetter than normal. For this reason,
the term climate change is preferred, rather than climate
warming or global warming. the rate of change seems
slow to some, with an increase of only a fraction of a
degree every decade when warming does occur, but
such small increases can lead to a higher probability
of summer drought if there is no concomitant increase
in precipitation. the result is slower tree growth, more
frequent forest fires, and less streamflow from the
mountains. Also, as will be discussed, diseases and
insect epidemics can spread in ways that have not been
observed before. And, with warmer temperatures, the
atmosphere can hold more moisture, thereby providing
the energy for extreme weather events. Flooding and
snowstorms could be more severe.
computer models generate specific predictions about
climate change and until recently have focused on large
areas. Some observers are skeptical of this approach,
but such models are required to synthesize all the geo-
physical, atmospheric, and ecological data and processes
that are involved. Modeling is used with confidence
for weather forecasting and launching space vehicles.
Warming projections based on models suggest that the
mean annual temperature in Wyoming and adjacent
states will increase by about 6°F by 2100, perhaps 7°F in
the southwestern part of the state—warmer than at any
time in the past 10,000 years. 21
computer modeling has been evolving for decades
as a tool for understanding complex systems, but such
models should be tested when possible with actual mea-
surements from specific places over long periods. Bryan
Shuman, paleoecologist and professor of geology at the
University of Wyoming, analyzed such data for Wyo-
ming. 22 He used records from 30 weather stations for
the period 1895-2007 to determine changes in three
variables: annual average temperature, the high tem-
perature on the coldest day of the year, and winter pre-
cipitation (november-March). His results, summarized
in fig. 3.9, show an increase since 1978 in the frequency

Climate Change in Western States

climate change is nothing new. As described in the pre-
vious chapter, tropical forests once grew in Wyoming's
Red Desert; millions of years later, glaciers extended
down to the foothills. However, the prevailing notion
has been that such changes are so slow that they hardly
mattered at human time scales. there were admonitions
to be prepared for occasional droughts and cold winters,
but few considered long-term trends. now, during the
past 30-40 years, worldwide records reveal increases in
air temperatures, and, not surprisingly, satellite images
have documented a steady, dramatic decline in Arctic sea
ice. Similarly, repeat photos show how mountain glaciers
are retreating wherever they still occur. Rocky Mountain
glaciers are no exception. 20
Questions about the validity of warming trends are
often asked when record low temperatures occur, or
about a drought after a year of heavy snowfall. clima-
tologists emphasize that there is a difference between the
weather that most people think about on a daily basis,
and climate, which is defined by the average conditions