Geoscience Reference
In-Depth Information
when it comes to an individual mountain
the case becomes less clear.
Nature is never simple, and undoubtedly
other factors besides global warming are in-
volved in the melting of the ice on Mount
Kilimanjaro. These could include decreased
precipitation; increased soot content of the
ice, causing more absorption of heat from
the sun; and local deforestation, which may
have caused a reduction of moisture in the
air. But the global loss of alpine ice and the
persistence of the Kilimanjaro ice cover
for thousands of years through a num-
ber of previous climate shifts (including
droughts) argue strongly that global warm-
ing is the villain of Kilimanjaro.
The other side of the coin is that the
warming is leading to permafrost melting,
which in turn leads to beach erosion, the
collapse of roads and buildings, the loss of
pipelines and sewage ponds, and the re-
lease of large volumes of methane and CO
2
.
Many changes in flora and fauna are occur-
ring. Some species are moving north and
replacing indigenous species; for example,
red foxes are displacing Arctic foxes. The
encroachment of trees and shrubs onto the
caribou tundra has reduced their food sup-
plies. The calving season of caribou in low
Arctic Greenland no longer corresponds to
the time of maximum food availability, so
fewer calves survive. Arctic plants start and
grow earlier in spring and are past their
energy-yielding prime when calving cari-
bou cows need them. There is also reduced
snow cover to provide insulation for hiber-
nating species.
Permafrost is perennially frozen ground,
both soil and rock, which underlies 20% to
25% of the Earth's land surface. It is par-
ticularly widespread in the Arctic. Perma-
frost does not always mean frozen water. It
ranges from rock with frozen water between
grains to soil with all pore spaces filled
with ice. Much permafrost was formed
thousands of years ago and is still main-
tained by current weather conditions. Per-
mafrost extends to depths as great as five
thousand feet in the Lena and Yana River
basins in northern Siberia, but recently
formed permafrost may be only ten feet or
so thick. Although generally restricted to
high latitudes, there is also an alpine form
Permafrost
Arctic lands are warming at five times the
global average, and as in all things, there
are advantages and disadvantages to such
changes. The good thing about the warm-
ing of the far north is that it could lead to
better farming conditions, improved ship-
ping in the Arctic Ocean when the North-
west Passage opens, and easier transpor-
tation to markets and consumers. On a
subtler level, musk oxen and caribou graz-
ing, trampling, and defecating help to
spread grasses, thereby attracting geese
and adding to the productivity of lakes.
Reindeer in Norway have benefited from
less snow and longer growing seasons,
which have reduced mortality and in-
creased the birth rate.
