| Dear
EarthTalk: How does growing human population,
and its resultant landscape changes, affect the flight paths
of migratory birds that might carry diseases?
-- Ronnie Washines, Toppenish, WA
| |
The
role of migratory birds in spreading bird flu is not
well understood, but waterfowl are a "natural
reservoir" of mostly harmless H5 and H7 influenza
A viruses. Recent research suggests that these viruses
may be mutating into more pathogenic (disease producing)
forms that can "jump the species barrier"
and infect people and other animals.
© Getty Images |
As
human population numbers grow, oceans of people seem to
spread out into every conceivable environment—even
the forests and estuaries used for eons by migratory birds
as nutrient-rich stopovers on their longer annual journeys
between feeding areas and birthing grounds.
Of
course, more human development means fewer habitats suitable
for such birds of passage (and other wildlife) as we “pave
paradise…” and put up parking lots. But tired
and hungry birds may not have the wherewithal or instinctual
coding to seek out alternative resting areas, so they make
do with habitat crowded and compromised by human incursion.
Close proximity to avian life hasn’t presented too
big of a problem for people in the past, but new concerns
about the spread of bird flu (the H5N1 virus) via infected
migratory birds (which presumably infect local populations
of domestic birds) does have some scientists worried that
persistent human expansion could indirectly lead to a disease
pandemic of global proportions.
According
to the World Health Organization (WHO), the role of migratory
birds in spreading bird flu is not well understood, but
we do know that wild waterfowl are a “natural reservoir”
of mostly harmless H5 and H7 influenza A viruses. But recent
research suggests that these viruses may be mutating into
more “pathogenic” (disease producing) forms,
such as H5N1 that can “jump the species barrier”
and infect people and other animals. “Recent events
make it likely that some migratory birds are now directly
spreading the H5N1 virus in its highly pathogenic form,”
reports WHO, adding that further spread to new areas is
expected. It is unlikely that the bird flu making headlines
a few years ago (the H5N1 strain), could lead to a human
pandemic. The vast majority who got sick had direct contact
with infected birds.
It
could be that the very sprawl that increases our chances
of catching bird flu—by bringing us and our poultry
farms into closer contact with disease-bearing migratory
birds—will protect us in the end. Humans have greatly
altered the landscape for agricultural and industrial purposes
and in creating urban settlements, points out wildlife biologist
Kevin Kenow of the U.S. Geological Survey’s Upper
Midwest Environmental Sciences Center. As such, it contains
less of the kinds of habitat migrating birds prefer—wetlands,
forests and prairies—and more of what adversely affects
them, such as human development, urban and agricultural
runoff, and other forms of habitat degradation. “Many
migratory birds that once flourished are now absent in altered
or degraded areas," he says.
Regardless
of the risk, scientists have yet to develop a vaccine to
protect against H5N1 in humans, but they are working on
it. Those who remain concerned should always cook poultry
to a temperature of at least 158 degrees Fahrenheit for
30 minutes (this heat kills the virus if it is present)
and wash hands with soap and warm water frequently (always
a good idea regardless). And look both ways before crossing
the street: At present, at least, your chances of getting
hit by a car are far greater than your chances of contracting
bird flu.
CONTACTS:
World
Health Organization; U.S.
Geological Survey’s Upper Midwest Environmental Sciences
Center.
Dear
EarthTalk: Since nitrogen oxide compounds are
components of smog and are common water pollutants, does
nitrogen-enriched gasoline create additional pollution?
-- Rick Oestrike, Poughkeepsie, NY
| |
Some
worry that adding nitrogen to gasoline increases nitrogen
oxide (NOx) pollution, which contributes to smog,
acid rain and other environmental problems. But proponents
argue that the detergent additive may have such beneficial
effects on engine operation and fuel system performance
that they outweigh the adverse effect of increased
NOx emissions.
© Patrick Houdek, courtesy Flickr |
It might seem
like adding nitrogen to gasoline is all the rage among oil
companies today, but the idea has been around for years.
The U.S. Environmental Protection Agency (EPA) requires
that automotive fuels sold in the U.S. contain detergents
to help scrub away pollution before it goes out the vehicle’s
tailpipe. Some manufacturers have found that adding nitrogen
to the detergent helps keep an engine cleaner by reducing
the carbon build-up in the gas tank that can in turn “gunk”
up the engine and lower performance.
The nitrogen
itself also has a direct cleaning effect, breaking down
carbon deposits that can harden on an engine’s moving
parts. “If too much collects, this gunk can negatively
affect engine performance, causing your car to burn more
oil, overheat and burn gasoline less efficiently,”
reports John Fuller on the How Stuff Works website. Valves
inside an engine are designed to let in a specific amount
of air and fuel, he adds; when that process is slowed by
carbon build-up, a car won’t perform up to its potential.
But while nitrogen-enriched
gasoline may provide a slight bump in engine performance,
some worry about adding to cars’ already substantial
pollution load, especially nitrogen oxide (NOx), which contributes
to smog, acid rain and other environmental problems. André
L. Boehman, a Penn State University engineering and fuel
science professor, says that the addition of more nitrogen
to the fuel mix “generally will increase NOx emissions.”
Boehman would like to see more research done so we can know
for sure if and how much additional NOx pollution is caused
by the use of nitrogen-enriched gasoline.
For its part,
Shell Oil, which last spring launched its own form of nitrogen-enriched
gasoline now for sale at all of its U.S. filling stations
(it is mixed into all three grades of gasoline the company
sells), denies that the additional nitrogen has any substantive
impact on pollution levels. “Most nitrogen in vehicular
NOx emissions does not come from gasoline,” the company
told The New York Times. “The nitrogen is primarily
from the incoming air that mixes with gasoline inside an
engine. NOx is produced when the nitrogen from the air reacts
with oxygen under high engine temperature and pressure conditions.”
Professor Boehman
concedes that “the detergent additive may have such
beneficial effects on engine operation, fuel system performance
and other related features of engine system operation that
they outweigh the adverse effect” of increased NOx
emissions. “For instance, if improved detergency helps
to increase fuel efficiency so that you burn less fuel,
you may slightly increase the NOx emissions rate per gram
of fuel burned, but end up with lower NOx because you burned
fewer grams of fuel.”
That said, it
is probably a good idea to avoid putting nitrogen in your
fuel unless you’re sure the gains will outweigh the
detriments. And until researchers know more, drivers might
focus instead on minimizing their own vehicles’ overall
gasoline consumption and fuel efficiency—and on substituting
other cleaner forms of transportation (walking, biking,
mass transit) whenever possible.
CONTACTS:
EPA
Fuels and Fuel Additives; How
Stuff Works; Shell. |
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