We're always trying to balance things: schoolwork, activities,
social life, chores, and all the rest. It's not easy. Tackling
one thing often means ignoring another. If that goes on too
long, it can threaten a person's physical and emotional health.
Picture yourself on a seesaw just after the
other person has leapt off suddenly. You've probably had times
when you felt exactly like that.
Just like us, our Earth needs balance. And that balance, scientists
warn, is precisely what human actions are undermining. In
the past few centuries, we've managed to change the world
in amazing ways: highways link whole continents, forests disappear,
dams tame mighty rivers, crops bloom in deserts, and buildings
scrape the sky. All that is wonderful in its way. But these
changes—and many more—have altered the planet's
balance in unfathomable ways.
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Once the trees come down, what will happen to this land?
Source: Washington Department of Fish & Wildlife |
THROWING THE EARTH OFF BALANCE
Here are just a few human actions—and their effects:
- Agriculture: High-tech farming sometimes treats
the land like dirt, which can lead to massive erosion
as well as runoff
that poisons water supplies.
- Deforestation: Needing lumber or land for farms
and towns, we've cleared vast areas of forest.
- Habitat Fragmentation: Countless animals have wound
up with only small, isolated pockets of habitat. That can
make it almost impossible for them to find
food and mates.
- Sprawl: Growing populations need space. To get
it, we're paving over more and more of the natural world.
- Water Control: Damming rivers and creating artificial
lakes greatly impact the surrounding land—and people.
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Watch the forest disappear as roads
and houses fragment the land. It's urban sprawl in action.
Source: John Rozum, NEMO |
BIODIVERSITY: A SIGN OF BALANCE
Maintaining Earth's balance is tricky
business. So many forces affect the environment that pinpointing
causes and effects is incredibly difficult.
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to enlarge image
Changes in the climate or habitat lead to loss of biodiversity.
Source: United Nations Environment Programme |
Scientists have found, however, that one
good measure of balance is whether we are maintaining biodiversity.
That's the full range of plants and animals living in an area—and
the relationships among them.
Loss of biodiversity can take a toll on human health. For
example, disease-carrying mice may increase in number when
their predators become scarce. One of the best-known examples
of what happens when biodiversity declines is the spread of
Lyme
disease.
ECOSYSTEMS IN ACTION
New York City recently saved several billion dollars. How? By
protecting farmland in its Catskill Mountains watershed
area. As rainwater runs through the creeks, streams, and wetlands
of this protected land, natural processes clean the water efficiently.
As a result, the city gets a steady flow of good drinking water.
And taxpayers don't have to pay for expensive equipment to clean
their water.
That's just one example of how humans benefit from "intact functioning
ecosytems"—or undisturbed ecosystems.
Researchers demonstrated recently that the world saves $33 trillion
a year, thanks to nature's "ecosystem services." Typical services
include flood control and storm protection (from wetlands),
fish harvests and related jobs (from coral reefs), and fertile
soil for farming (from grasslands).
Other studies have found that an undisturbed
ecosystem is worth nearly twice as much—in terms
of the value of products it can produce—than
the same amount of developed land. The United States
Department of Agriculture calculated that by removing
pollutants from city air, trees also cut our health
costs. Trees are nature's efficient air-cleaning machines.
In fairy tales, walking into the
woods often means trouble. Forests are painted as
dark, wild places filled with unseen dangers. Unexplored
wilderness can be frightening. But it also
promotes our well-being in ways we are only beginning
to understand. |
Redwood Forest
Source: National Park Service |
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Scientists estimate that several million to
100 million species of plants, animals, and
other organisms share the Earth. This huge
range shows how much we still have to learn.
