What is "organic" farming?
Organic
farming means relying upon natural fertilizers, pesticides,
and herbicides instead of synthetic chemicals. This can be
important to human health and to the health of the planet
because chemicals used in agriculture are one of the chief
sources of water pollution. No one knows, furthermore, the
degree to which exposure to these chemicals may weaken our
immune
system or cause cancer
and other diseases.
While government agencies are still working on the exact definition
of organic farming, everyone agrees that organic farmers do
not use antibiotics.
This is important. More and more of agriculture relies on
antibiotics to prevent disease in animals that are raised
in factory-like conditions. People who eventually eat these
animals also ingest the antibiotics. This can have many harmful
effects, and can make antibiotics less effective for when
our body actually needs them to fight disease. Farmers sometimes
spray antibiotics on fruits and vegetables, which can also
wind up in the human body.
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Is genetically modified food good or bad?
Many people feel very strongly about this question, and it is
important to separate the facts from the emotions. Genetically
modified food can decrease our dependence upon chemicals such
as pesticides. It also has the potential to feed huge numbers
of people who suffer from malnutrition. These are both extremely
important accomplishments. But genetically modified seeds can
escape from farms and breed with plants growing in the wild.
No one knows the short or long-term impact of this. We also
do not know the long-term effects—if any—of genetically modified
food on people. GM food has been found, for example, to trigger
allergic reactions in some people.
Genetically modified seeds can also increase the dependency
of farmers, particularly in the developing world, on large corporations
that create, manufacture, and price them.
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Sure cutting down forests harms the environment, but don't
people have to cut down trees to make a living?
Numerous studies show that people in developing
countries (where most of the forest loss occurs) would have
a better life and be better able to feed themselves if they
sold the natural products from the forests rather than cutting
down the trees and selling the lumber-or turning forests into
farms.
Stripped of its green cover, rainforest soil becomes barren
and thin. Often within a short period of time, farmers and ranchers
abandon it and move on to new places, leaving the former rainforest
a wasteland. Soil erodes and the original tree canopy never
grows back. Once deforestation
occurs and the balance of nature is disrupted, the land can
become a breeding ground for insects and other animals that
carry diseases such as malaria
and leishmaniasis.
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How can a lot of animals being around be good for human health?
Balance in nature is often good for human health. The best way
to see this is to examine what happens when the balance is destroyed.
You've probably heard of Lyme disease and may even have been
asked to stay away from certain areas to avoid the ticks that
carry the disease.
Ten or twenty years ago, Lyme disease wasn't much of a problem.
Here's what happened: As suburbs
in states such as Connecticut (where scientists first identified
Lyme disease) spread into wooded areas, people increasingly
came into contact with wildlife. At the same time, predator
animals such as foxes died, leaving behind deer and mice, whose
population began to grow because the animals that ate them were
no longer around (and because there was less human hunting).
Deer and mice carry the tick that transmits the bacteria
that cause Lyme disease. The result: As deer and mice lived
closer and closer to humans, ticks had more opportunities to
bite humans—and spread the disease.
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Why do dams that are built to provide electricity and control
floods also harm human health?
Dams can make great contributions. But like most everything
that changes the balance of nature, they can also do great harm.
Dams create artificial lakes that can be breeding grounds for
insects and other disease-carrying animals. Schistosomiasis,
for example, often spreads via snails that thrive in the stagnant
or slow-moving water that is trapped by dams. Large dams can
also force huge numbers of people to move. Construction of the
Three Gorges dam, now under construction along the Yangtze River
in China, for example, has caused about two million people to
uproot and move their homes.
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What kind of city is the healthiest?
Some cities are better than others for human health. A health-friendly
city has planned growth, public transportation, and uses other
measures that cut people's reliance on motor vehicles; e.g.,
schools within walking distance. The result is less air pollution
and few respiratory diseases like asthma.
Fewer cars means fewer roads and parking lots-the hard, dense
surfaces that create the heat
island effect, which makes cities hotter and creates problems
associated with global
warming. Fewer roads and parking lots also mean that less
runoff
water (that is polluted with chemicals from car exhaust and
other sources) will reach the city's watershed
area, where such chemical pollutants kill wildlife.
Cities with trees, shrubs and parkland are healthier too. They
cool the air, and offer more opportunity to relax and escape
the stresses that can come with urban life. Trees and other
plants also remove pollutants from the air—naturally.
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What does survival of microbes on the moon have to do with
our health?
In the early 1970s, astronauts landing on the moon found microbes
flourishing on a camera that had landed with an unmanned flight
in 1967. Scientists were shocked. They had not expected microbes
to survive the extremely low temperatures, lack of air, and
other harsh conditions. This demonstrated that microbes—including
microbes that cause disease—are excellent travelers. As more
and more ships and planes carry people and goods from place
to place across the globe, the ability of microbes to hitch
a ride and survive means more diseases are more likely to spread
to more places more quickly.
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Diseases like leishmaniasis and giardias seem to occur far
away. Sure, I care about other people, but do they really have
anything to do with me?
In today's global world, everyone is connected to everyone else.
If diseases plague people in a faraway country, they can have
an impact on the economy and jobs in developed countries like
the U.S. Even more importantly, the presence and the spreading
of such diseases indicate that people are cutting down forests,
polluting water, and contributing in other ways that disrupt
the balance of nature.
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If we can get medicines from human-made chemicals, why do
we need plants?
Human-made chemicals do provide countless medicines. But even
the best scientists, working the most powerful computers and
large databases, cannot create medicines whose chemicals are
as complex as those that nature designs. Nature does things,
furthermore, in ways that humans can't imagine-or replicate.
One example is paclitaxel,
a chemical that fights many types of serious cancers.
It comes from the Pacific Yew tree and kills cancerous cells
by making them too rigid to reproduce. Before they started studying
chemicals from the Pacific Yew, scientists had never even thought
of trying to kill cancer cells in this manner.
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Why do plants make medicines that help people?
Like all living things, plants work to survive. Consider all
the things that can harm plants: insects, microbes, and animals
that want to eat them. So over hundreds of millions of years,
plants have devised an arsenal of chemicals that kill or repeal
their enemies. Just like your body has an immune
system that fights off microbes
that give you a cold, plants have a defensive system that works
hard to fight off microbes that make them sick.
Many of these defensive chemicals are extraordinarily powerful
and complex for the simple reason that plants cannot run away.
They have to stay and fight whatever is threatening them. These
same chemicals can also fight the microbes that cause diseases
in humans, or have other effects that promote human health.
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Can animals like snakes and sharks really save our lives?
Yes. We know that snake venom can harm or kill people. Its function
in nature is to kill a snake's enemies. But the powerful bioactive
(having an effect on living things) chemicals in snake venom
can also be transformed into medicines. One type of venom, for
example, kills animals (and sometimes humans) by lowering blood
pressure to such a degree that it can become fatal. One chemical
from this venom, given in modified and weak doses, may become
a new medicine that prevents and treats high
blood pressure, one of the world's leading killers of people
everywhere.
Likewise, we think of sharks as something that can harm us.
And you certainly wouldn't want to be at the business end of
a hungry shark. But at the same time, sharks have much to teach
us. For reasons that scientists do not yet fully understand,
sharks rarely get sick. Studying the chemicals that many sharks
produce has already yielded promising clues that may lead to
exciting new medicines to treat cancer
and other diseases.
Such examples show the wide range of mysteries that nature offers-and
the importance of biodiversity
to human health.
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Can an infectious disease cause a species to go extinct?
While destruction of habitat is the major contributor to species
loss, infectious
diseases can weaken a species and contribute to it being
threatened with extinction.
Scientists have documented one time when infectious disease
clearly was the final cause for the disappearance of a species—the
Polynesian tree snail, which went extinct in 1996. This is called
extinction by infection.
What disease is causing frog populations to decline?
In 1998, scientists discovered that a fungal
disease, called chytridiomycosis, had infected a wide range
of frog species around the world. Experts believe that the bull
frog, sold internationally through the food and pet trade, carries
this disease. As a result, chytridiomycosis spreads as bull
frogs come into contact with other species of frogs.
What is pathogen pollution?
Pathogen
pollution refers to the introduction of disease-causing microbes
(pathogens) and/or their hosts (infected individuals) to new
locations around the world. European bird species, including
pigeons and the house sparrow, for example, introduced West
Nile virus to the United States.
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What is an emerging infectious disease (EID)?
EIDs include diseases that have jumped from wildlife populations
to humans, diseased that have become more frequent, and diseased
that are entirely new to science. Examples of EIDs include HIV/AIDS,
West
Nile virus, and SARS.
