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FOREST
CONSERVATION NEWS TODAY
Ecosystem
Collapse Can Result from Gradual Changes
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10/12/01
OVERVIEW
& COMMENTARY by Forests.org
The sky
is falling! Around the world ecosystems
are collapsing -
threatening
the existence of productive ecological systems and all
the
World's species - including humans. A
shocking and
groundbreaking
new scientific study in the journal "Nature"
concludes
that many of the World's ecosystems are moving rapidly from
their
natural condition and seeming stability to very different and
diminished
conditions. Conventional scientific and
conservation
thinking
has been that ecosystems - be they lakes, oceans, coral
reefs,
woodlands or deserts - respond slowly and steadily to climate,
nutrient,
habitat and other environmental shifts.
This
new study shatters this paradigm - indicating that after decades
of
continuous change imposed by human activity - many of the world's
natural
ecosystems appear susceptible to sudden catastrophic change.
In
ecosystems around the World, "gradual changes in vulnerability
accumulate
and eventually you get a shock to the system -- a flood or
a
drought -- and boom, you're over into another regime. It becomes a
self-sustaining
collapse." These cataclysmic
alterations result
from
the breakdown of resilience of an ecosystem relentlessly pushed
away
from its natural origins.
This
has important implications for conservationists and policymakers
who may
base decisions on the misconception that ecosystems change
gradually. "Ecosystems may go on for years exposed
to pollution or
climate
changes without showing any change at all and then suddenly
they
may flip into an entirely different condition, with little
warning
or none at all." The study
concludes that coral reefs and
tropical
forests are vulnerable, as are northern lakes and forests.
Global
warming is now adding another destabilizing factor. The
authors
recommend rebuilding ecosystem resilience, rather than
controlling
an individual disturbance to a given ecosystem.
"We
should not be complacent about the response of ecosystems to
ongoing
global changes in environment... What may seem gradual and
unimportant
could produce big, undesirable changes in ecosystems and
the
productivity of food and forestry systems upon which we all
depend." Indeed, the sky is falling.
g.b.
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TEXT STARTS HERE:
ITEM #1
Title: Gradual change can push ecosystems into
collapse
Source: Copyright 2001 Environmental News Network
Date: October 12, 2001
After
decades of continuous change imposed by human activity, many of
the
world's natural ecosystems appear susceptible to sudden
catastrophic
change, an international consortium of scientists
reported.
Coral reefs and tropical forests are vulnerable, as are
northern
lakes and forests, the team has found.
Marten
Scheffer, an ecologist at the University of Wageningen in the
Netherlands,
said, "Models have predicted this, but only in recent
years has
enough evidence accumulated to tell us that resilience of
many
important ecosystems has become undermined to the point that
even
the slightest disturbance can make them collapse."
Scheffer
is the lead author of the study published Oct. 11 in the
scientific
journal Nature. He is one of five authors of the paper
whose
contributors include experts on an array of different ecosystem
types.
A
gradual awareness is building in the scientific community that
stressed
ecosystems, given the right nudge, are capable of slipping
rapidly
from a seemingly steady state to something entirely
different,
said coauthor Stephen Carpenter, a limnologist at the
University
of Wisconsin-Madison and immediate past president of the
Ecological
Society of America.
"We
realize that there is a common pattern we're seeing in ecosystems
around
the world," said Carpenter, an authority on lakes.
"Gradual
changes in vulnerability accumulate and eventually you get a
shock
to the system, a flood or a drought, and boom, you're over into
another
regime. It becomes a self-sustaining collapse."
An
understanding that ecosystems engage in a delicate balancing act
has
emerged as scientists have become more skillful at assessing
entire
ecological systems. Studying how catastrophic ecological
change
has occurred in the past can cast light on how today's
ecosystems
may be affected.
Six
thousand years ago, parts of what is now the Sahara Desert were
wet,
and its lakes and swamps held crocodiles, hippos, and fish.
"The
lines of geologic evidence and evidence from computer models
show
that it suddenly went from a pretty wet place to a pretty dry
place,"
said Jonathan Foley, a University of Wisconsin-Madison
climatologist
who is also a coauthor of the Nature paper.
Another
drying area is found around Central Asia's Aral Sea. As a
result
of its shrinking size due to the loss of recharge water and a
high
rate of evaporation, islands are gaining more surface area. As
the sea
level continues to drop, more of the sea floor is exposed,
and the
islands and peninsulas become connected land, the existing
Aral
Sea could become several separate bodies of water - forming new
lakes.
Since
1960, most of the fresh water has been diverted for
agriculture,
and salinity levels have steadily increased.
"Nature
isn't linear," Foley said. "Sometimes you can push on a
system
and push on a system, and finally, you have the straw that
breaks
the camel's back."
Constant
change is a fact of life for most ecosystems, the authors
write,
whether from increased nutrient levels or human exploitation.
Global
warming is now adding another destabilizing factor to put
ecosystems
in a far more precarious situation than scientists had
previously
imagined.
"All
of this is set up by the growing susceptibility of ecosystems,"
Carpenter
said. "A shock that formerly would not have knocked a
system
into another state now has the potential to do so. In fact,
it's
pretty easy."
Carpenter
cited Lake Mendota, an urban lake in Madison, Wis., that is
perhaps
the most studied lake in the world. It has seen a steady
influx
of nutrients such as phosphorus - chemical runoff from farms
and
suburban lawns - as the land around it has been chemically
enriched
and then developed.
"Over
the past 150 years, we've put a huge amount of phosphorus into
the mud
of Lake Mendota, and it's prompted a lot of algae growth in a
lake
that was once very clear," Carpenter said. In 1993, scientists
watched
nutrient levels rise sharply after a single heavy rain washed
nutrients
into the lake. "This phosphorus buildup has made it easy
for
Lake Mendota to go into a eutrophic state," characterized by
green
surface scums, Carpenter said, and reversing eutrophication is
hard
because of the phosphorus buildup in soils and sediments.
Similar
patterns of ecosystem degradation are evident on coral reefs
and in
forests. If large enough, forests can influence the weather or
even
have their own weather systems by facilitating the movement of
water
from the surface of the earth to the atmosphere.
Overexploitation
of those forest resources, said Foley and Carpenter,
can
have profound effects beyond the simple extraction of a resource
such as
wood.
"The
idea that nature can suddenly flip from one kind of condition to
another
is sobering," said Foley, who suggested that changes can be
irreversible.
"For hundreds of years, we've been taught to think in
very
linear ways; we like to think of nature as being simple. But now
we know
that we can't count on ecosystems to act in nice simple
ways."
Says
Carpenter, "Although it's possible to push things in the other
direction,
to a certain extent, restoring a system depends on the art
of the
possible. What can you do within the constraints of politics
and
economics to turn back the tide?"
ITEM #2
Title: One more 'push' may crash some ecosystems
Source: Copyright United Press International
Date: October 10, 2001
Byline:
LIDIA WASOWICZ, UPI Senior Science Writer
Man's
environmental battering has left some ecosystems in such a
fragile
state, the slightest alteration, from a dry spell to a fire,
may
push them into a catastrophic collapse, an international
consortium
of scientists asserts.
The
authors of the review in the British journal Nature recommend
rebuilding
ecosystem resilience, rather than pursuing the current
common
practice of controlling an individual disturbance, be it an
invasive
exotic species or a disease.
Conservation
and other policies are based on the long-standing view
that
ecosystems -- whether lakes, oceans, coral reefs, woodlands or
deserts
-- respond slowly and steadily to climate, nutrient, habitat
and
other environmental shifts.
In
dramatic contrast, the investigators paint a picture of
unexpectedly
sudden, drastic switches of state, from lush, lake-
dotted
forests teeming with plants and animals to scorching, parched
deserts
devoid of all but the hardiest of lifeforms, for example. At
the
root of such cataclysmic alterations is the breakdown of
resilience
of an ecosystem relentlessly pushed away from its natural
origins,
the study authors suggested.
"We
systematically alter conditions on the earth, such as temperature
and
nutrient levels. We usually assume that things are okay if nature
is not
changing too strongly and assume that we may always reverse
change
by taking 'a step back' if things seem to become too bad,"
lead
study author Marten Scheffer, an ecologist at the University of
Wageningen
in The Netherlands, told United Press International.
"Our
article shows that this does not hold. We may see little effect
until
the breakpoint. Once the catastrophic change has occurred, the
way
back is typically very difficult."
While
nature has spawned such variations through the ages, a new
unnatural
force has entered the scene, the scientists said.
"We
are now witnessing a human-induced, tremendously rapid change in
conditions,
compared to what happened in most of the ancient past,"
Scheffer
said. "None of the changes ahead will stop nature from
functioning
in one way or another. However, some of the rapid
switches
may take us by surprise and cause not only a tremendous loss
of
biodiversity but also play havoc with human use of nature in an
economic
sense as well as in a wider sense."
An
assessment, over long periods and entire ecological regimes,
points
to the invisible instability of stressed systems, which, given
the
right nudge, can suddenly plunge from seeming steadiness into
distressed
discord, scientists told
UPI.
"We
realize that there is a common pattern we're seeing in ecosystems
around
the world," said study co-author Stephen Carpenter, a
limnologist
at the University of Wisconsin, Madison. "Gradual changes
in
vulnerability accumulate and eventually you get a shock to the
system
-- a flood or a drought -- and boom, you're over into another
regime.
It becomes a self-sustaining collapse."
The
findings have important implications for conservationists and
policymakers
who may base decisions on a misconception, scientists
said.
"In
approaching questions about deforestation or endangered species
or
global climate change, we work on the premise that an ounce of
pollution
equals an ounce of damage," said co-author Jonathan Foley,
director
of the Center for Sustainability and the Global Environment
at the
Institute for Environmental Studies at UW-Madison.
"It
turns out that assumption is entirely incorrect," he told UPI.
"Ecosystems
may go on for years exposed to pollution or climate
changes
without showing any change at all and then suddenly they may
flip
into an entirely different condition, with little warning or
none at
all."
In one
of the more striking examples, a lush, wet playground of
hippos,
fish and crocodiles that abounded in lakes and swamps
suddenly
turned into the largest arid area on Earth, the Sahara
Desert.
"The
sudden catastrophic desertification in the Sahara 5,000 years
ago was
caused by gradual change in irradiation due to gradual change
in the
Earth orbit," Scheffer said.
"The
lines of geologic evidence and evidence from computer models
show
that it suddenly went from a pretty wet place to a pretty dry
place,"
Foley added.
Lake
Mendota in Madison provides a more contemporary example. Algae,
fat
from a steady diet of chemicals from runoff from farms and
suburban
lawns, have turned the once pristine, crystal-clear waters
into a
murky cesspool of green slime.
"Over
the past 150 years, we've put a huge amount of phosphorus into
the mud
of Lake Mendota," Carpenter said. "This phosphorus buildup
has
made it easy for Lake Mendota to go into a eutrophic state."
Reversing
the trend will be all the more difficult because the
thicket
of sun-blocking algae has been suffocating lake-bottom plants
that
are natural-born cleaners.
"Even
if fertilizer runoff is reduced in efforts to clean up the
lake,
it will take a lot more work to restore the lake without the
help of
the big plants that had kept the mud from stirring up,
keeping
the water clear," Foley said.
At most
immediate risk are numerous tropical ecosystems, freshwater
rivers
and lakes and coastal estuaries and other marine systems,
Carpenter
told UPI.
Evidence
supporting the author's assertions spans the globe,
scientists
said.
"I
find that my own work in southern New Mexico, where we have seen a
widespread
change from semiarid grassland systems that were
productive
rangelands to arid shrublands, substantiates what these
authors
describe in the desert regions," said William Schlesinger,
James
B. Duke professor of biogeochemistry and dean of the Nicholas
School
of the Environment and Earth Sciences at Duke University in
Durham,
N.C.
"Abrupt
environmental change has affected these ecosystems
worldwide,"
he told UPI.
Similar
patterns of degradation are evident on coral reefs and in
forests.
If large enough, forests can influence the weather or even
have
their own weather systems by facilitating the movement of water
from
the surface to the atmosphere, investigators said.
Increasing
human population and anticipated global climate changes
will
bring additional stresses, though some may be somewhat less than
projected,
if the authors of another Nature study are correct.
Yiqi
Luo and his team at the University of Oklahoma in Norman suggest
soil
microbes may adjust to global warming so their contribution to
the
release of the notorious greenhouse gas carbon dioxide may be
less
than predicted.
All
models have assumed the CO2 from respiration of bacteria, plant
roots
and fungi would rise along with Earth's temperature, which is
expected
to increase between 1.4 degrees Centigrade and 5.8 degrees C
(2.5
degrees Fahrenheit to 10.4 degrees F) over the next century as a
result
of greenhouse gas emissions. But, Luo and crew found that
under
artificially increased temperatures, soil respiration on the
test
grassland plots did not go up as much as had been forecast.
"Soil
respiration is a major contributor to global carbon cycling,
thus
only a small decrease could compensate for man-made emissions,"
said
Lindsey Rustad of the U.S. Department of Forest Service in
Durham,
N.H., who wrote an accompanying News and Views article.
Nevertheless,
any climate change may add to a situation that already
appears
to be more precarious than anyone had imagined, the
scientists
said.
"We
should not be complacent about the response of ecosystems to
ongoing
global changes in environment," Schlesinger said. "What may
seem
gradual and unimportant could produce big, undesirable changes
in
ecosystems and the productivity of food and forestry systems upon
which
we all depend."
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