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Such vast damage in those forests, needless to say, will have profound
impacts in the entire ecosystem, changing the water cycle, the growth
paterns across the formerly wooded landscape, and much more. his
transformation is largely due to the activities of a single species and per-
fectly illustrates how the complex interactions between species in ecosys-
tems make them terribly vulnerable to climate change.
But changes due to the expansion of single species throughout a
region are relatively subtle compared to the even broader transforma-
tions that every ecosystem will have to undergo. The effect of pine beetles
in western forests pales in comparison to the even more dramatic effects
of rising temperatures on the water cycle. The warming of the ecosystem
increases evaporation and causes the gradual drying of the land, kill-
ing trees even where they are not vulnerable to insects. Recent research
into the state of forests throughout the western United States shows that
they are already experiencing a demographic shift—an increase in the
number of trees dying and a decrease in the number of new trees grow-
ing per year—and that as a result they are approaching “thresholds for
abrupt dieback.” The drier conditions as well as the increasing activity of
various species of insects is leading to rising mortality in those forests. 30
Evidently, climate change often works through several effects at once,
each compounding the impact of others, creating conditions that are
worse than any single process could bring about.
Similar changes are taking place in every region of the United States.
In the Northeast, for example, climate change will drive the maple for-
ests further north, eventually depriving the region of the autumn colors
distinctive to the region, and the rising seas and increasing intensity of
storms will lead to greater storm surges, damages to wetlands, coastal
flooding, and erosion (as the stunning effects of Superstorm Sandy have
made abundantly clear). The Southeast will become so hot and dry that
its pine forests may disappear; oxygen depletion in the region's lakes will
kill off fish in lakes and streams; and more powerful tornadoes and hur-
ricanes will damage inland regions and coastal areas alike. The Southwest
faces a dramatically altered future, one in which droughts will be longer
and more intense than they were in the past, causing rivers and lakes to
diminish and fires to spread more easily. The reduction in the snowpack
over the Sierra Nevada in eastern California will lead to severe water
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