Are humans really so tiny and insignificant that their activity
makes no difference on climate? Some people say so but, if you
are of this opinion, you might change your mind once you read
how much human activities affect the Earth's crust. For
instance, the amount of rock and soil we move every year would
fill the whole Grand Canyon in about 50 years. An excerpt from
Ugo Bardi's "Depleting the Earth," a book being prepared in
collaboration with the Club of Rome. The amounts of minerals
extracted nowadays is immense and it becomes even larger if
consider as “mining” the use of fertile soil in agriculture
which is consumed by the process called erosion. It is estimated
that about 4 billion tons of agricultural soil are eroded in the
United States alone and dumped into the oceans every year (1).
In the whole world, the total amount has been estimated as 75
billion tons per year by Pimentel et al. (2) and as 120 billion
tons per year by Hooke (3). These amounts dwarf those created by
natural erosion, at least on