Environmental Engineering Reference
In-Depth Information
upheavals, and mysterious mass extinctions regularly taking their toll on
biodiversity. The last of these that occurred some 200 million years ago
wiped out over 75% of the species! The resilient barren earth fought back
for tens of millions of years to repopulate and reach the present level of
biodiversity. Thankfully, the conditions are again just right to sustain life
on Earth, with ample liquid water, enough solar energy to allow autotrophs
to spin out a food web, a stratospheric ozone layer that shields life from
harmful solar UV radiation, enough CO
2
to ensure a warm climate, and
oxygen to keep the biota alive. We owe life on Earth to these natural cycles
in complex equilibrium. However, the apparent resilience of the biosphere
to human interference can often be misleading as the dire consequences
of human abuse of the ecosystem might only be realized in the long term.
Figure 1.1
shows the growth in world population along with 10-year
population increments.
