|Humans altering Earth for the worse
Thursday, August 5, 1999
Close to 50 percent of the Earth's land mass has been altered from its
original state by humans.
Recent research shows that humans are responsible for serious changes in
the Earth's chemical, biological and physical structure — and the changes
are not for the better.
The data indicate that the human transformation of lands and oceans is
severely disrupting the fragile ecological systems that people depend on
for the basics of existence such as clean air, clean water, food and
shelter, as well as safety from natural disasters such as flood and drought.
The data was collected and analyzed by Dr. Jane Lubchenco, distinguished
professor of Zoology of Oregon State University, and Dr. Harold A. Mooney
and Dr. Peter M. Vitousek of Stanford University. Lubchenco presented their
findings this week at the XVI International Botanical Congress hosted by
the Missouri Botanical Garden in St. Louis.
Some of the findings include:
--Close to 50 percent of the land surface of the planet has been altered
from its original state by humans, such as filling wetlands, converting
tall grass prairies into cornfields, or converting forests into urban areas.
--Humans have more than doubled the amount of available nitrogen in the
environment because of excess fertilizer use and burning of fossil fuel.
--Rates of extinction are 100 to 1,000 times what they would be without
human-induced changes in the planet. On land, this is largely caused by
habitat loss and species invasions that are crowding out native species. In
water, this is caused by overfishing, as well.
--The year 1998 was Earth's hottest on record, as human activities continue
to increase the concentrations of carbon dioxide and other heat-trapping
gases in the atmosphere.
While the affect of humans on the available land mass is obvious — just
drive Interstate 80 through the Midwest in the United States — the affect
on the oceans is not as apparent.
Lubchenco's research showed that approximately 50 "dead zones" — areas of
water with little to no oxygen — have developed in ocean coastal areas, the
worst of which is in the Gulf of Mexico near the mouth of the Mississippi
River. This dead zone is caused by high levels of phosporus and nitrogen
from agricultural run-off that ends up in the river and ultimately in the
"We've long thought of oceans as having an infinite ability to provide food
and other goods and services to humans. But the massive human-wrought
changes in our oceans are impairing their ability to function as we assume
they will," said Lubchenco. "We're degrading the water, changing our
coastlines, filling in our estuaries and changing our rivers. And we're
witnessing many signals of the problems that will result from these
changes, including toxic algal blooms, coral bleaching and sudden
disappearance of fish from key fisheries."
According to Lubchenco, humans are degrading the Earth's rivers, oceans and
lakes in many ways:
Half of the mangrove forests, which serve as estuaries in the tropics, have
been lost to a combination of coastal development and conversion to
Global aquaculture now accounts for more than one-quarter of all fish
consumed by humans. In the case of shrimp and salmon, which comprise the
fastest growing segment of aquaculture, two to three pounds of fish are
needed to grow one pound of the raised seafood. Thus this practice is
depleting the oceans of food for wild fish, birds and marine mammals.
About 3,000 species of marine life are in transit in ballast water of ships
around the world, resulting in a serious invasion of non-native species in
our waterways. A minor but increasing contributor to the problem is escape
of non-native fish and plants from aquariums.
The human alterations to the ecological systems of the Earth are affecting
more than just food supply. "In addition to the direct [ecological]
services of food, fiber, shelter and medicines, many other inter-dependent
services are being disrupted," Lubchenco said. For example, forests,
grassland and coral reefs contribute to flood control and climate
regulation. Mangroves, estuaries, coral reefs, and kelp forests protect
shores from erosion besides providing nursery areas or spawning habitat for
economically important species.
The environmental changes that are taking place can have political
repercussions as well. "Scarce resources such as water or fishing rights
lead to battles between states and nations. Environmental degradation
resulting in food shortages lead to civil unrest and migration into
neighboring countries," said Lubchenco. This situation will only worsen as
the world population continues to increase.
But with the increasing number of people around the world taking notice of
environmental issues and getting involved in finding solutions, Lubchenco
does feel hopeful that the situation can turn around. "It is encouraging
that there is an increasing focus on the part of the private sector,
religious groups, and individual citizens to take responsibility and
undertake innovative action."
"As inhabitants of Earth, we need to take stock of these massive changes,
understand their implications and change our direction, " Lubchenco said.
"We are currently inattentive stewards. It is in our best interests to be
more fully engaged in ensuring our own health, prosperity and well-being."
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