Michigan, November 3, 2004 (ENS): Humans are
stripping soil from the surface of the Earth far faster
than nature can replace it, an analysis by a University
of Michigan geologist shows.
Bruce Wilkinson, a University of Michigan professor
of geological sciences, says human activity causes 10
times more erosion of continental surfaces than all
natural processes combined. Wilkinson will present his
findings November 8 at a meeting of the Geological Society
of America in Denver, Colorado.
People have been the main cause of worldwide erosion
since early in the first millennium, and many researchers
have tried to assess the impact of human activity on
soil loss, Wilkinson said, but most have only guessed.
Wilkinson used existing data on sedimentary rock distributions
and abundances to calculate rates of natural erosion
from glaciers and rivers compared with that caused by
human activity - mainly agriculture and construction.
"If you ask how fast erosion takes place over
geologic time - say over the last 500 million years
- on average, you get about 60 feet every million years,"
But in those parts of the United States where soil
is being eroded by human agricultural activity, the
rate averages around 1,500 feet per million years, and
rates are even higher in other parts of the world.
Natural processes operate over areas larger than those
affected by agriculture and construction, but even taking
that into account, Wilkinson said, "the bottom
line is, we move about 10 times as much sediment as
all natural processes put together."
"This situation is particularly critical,"
Wilkinson said, "because the Earth's human population
is growing rapidly and because almost all potentially
arable land is now under the plow."