A WORLD IN CRISIS

O

ver three billion years ago, just before the first life

forms arose, Earth’s surface and climate were

inhospitable by modern standards, but contained

abundant raw materials. As early life forms evolved,

they began to use the sun’s energy to exploit Earth’s

resources. Eventually they shaped the landscape,

altered the global climate, and modified the

chemical makeup of the ocean and soils. These

changes, along with shifts in Earth’s orbit and

the sun’s energy output, created conditions in

which the millions of species that now inhabit

our planet arose and adapted.

Today, the human species is the most

significant agent of environmental change on

our planet. Our intellectual capacity has even

made it possible for us to venture into space,

allowing us a view of the uniqueness of our

planet in the solar system (see photograph).

However, our burgeoning population is

overwhelming Earth’s regenerative capacity. We

transform forests, prairies, and deserts to meet

our needs and desires, and we consume ever

increasing amounts of Earth’s abundant but finite

resources—rich topsoil, clean water, and breathable

air. We are eradicating thousands upon thousands of

unique species as we destroy or alter their habitats. In

2009, a total of 5566 species were classified as endangered

worldwide (see insert). Our activities now affect processes,

including climate and nutrient cycles, from the local to the global level.

This book introduces the major environmental impacts that humans have

on Earth, and considers ways to reduce those impacts that undermine economic, social, and

environmental well-being. Most importantly, it explains why we must minimize human impact on

our planet. We can’t afford to ignore the environment because our lives, as well as those of future

generations, depend on it. As a wise proverb says, “We have not inherited the world from our

ancestors, we have only borrowed it from our children.”

1

The Environmental

Challenges

We Face