Climate Change Will Happen to You - Stolen Future, Broken Present: The Human Significance of Climate Change - page 9

public health, and local and regional economies. We may end up living in
natural systems that are not only rapidly changing, but also much weaker
and in some cases dying out altogether. We'll be far less comfortable right
where we live than we once were. 27
At first changes of this kind may seem overstated. For example, the
fact that the zones with a particular average annual temperature will be
shifting northwards might not initially sound so bad. After all, one might
argue, ecosystems further south hang together quite well; wouldn't they
fare equally well if they moved to the north? But many species are less
able to compete with or displace species that already live in regions to
the north, to reproduce quickly and thus adjust to new living conditions,
and to move across miles of territory in a few years, suggesting that some
portions of an ecosystem will migrate successfully while others will not.
Some species might be mobile enough to move on, but if they did so,
would lose access to their sources of food or to the habitats (river valleys,
mountains) where they previously flourished. Forms of life that flour-
ish in mountainous terrain may have only so far up the mountainside
to migrate before running out of room. Unlike animals or birds, plants
rooted in the soil might find it difficult to move quickly into new terrain.
Many species will adapt to new conditions, but many others will not.
Studies show that in the second half of the twentieth century, species on
average migrated toward the poles at the rate of four miles per decade,
while the zones in which they live—those defined by specific average
temperatures—have migrated far more quickly, about thirty-five miles
per decade. 28 Over time, as warming continues, the species that can't
move very fast will find themselves within much warmer temperature
belts, will be unable to flourish within a climate too hot for them, and will
succumb to natural forces.
Such pressures can take many forms. Consider the changes taking
place in the pine forests of western North America, especially in British
Columbia. The pine beetle, a native insect in those regions, is now repro-
ducing at a much greater rate than before; thanks to the warming winters,
the warmer summers, and the reduction in summer precipitation, it is
becoming a much more dominant species in those habitats than before.
As a result, it is killing millions of acres of trees, converting the boreal for-
est of British Columbia from a carbon sink to a net emiter of carbon. 29