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WORLDWIDE FOREST/BIODIVERSITY CAMPAIGN NEWS

Studies Document Ease Of Ecosystem Disruption

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Forest Networking a Project of Ecological Enterprises

http://forests.org/ -- Forest Conservation Archives

http://forests.org/web/ -- Discuss Forest Conservation

4/17/99

OVERVIEW & COMMENTARY by EE

The case is made for the management and protection of whole

ecosystems, not individual species. This is based on research that

indicates that ecosystems may be more vulnerable to change or loss of

"minor" species than previously thoughts. Experiments in the marine

rocky intertidal shores of the Oregon coast make a case for managing

whole ecosystems, "since ecosystem health is likely to depend on the

interactions of many species, the abundant ones as well as the rare

ones, the keystones and the 'not-so-keystones'." If this indeed is

the case, the justification for allowing large remaining wilderness

areas to not be manipulated and remain in a relatively natural

condition is strengthened.

g.b.

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RELAYED TEXT STARTS HERE:

Title: Studies Document Ease Of Ecosystem Disruption

Source: Oregon State University, via econet bitl.ecolog conference

http://www.eurekalert.org/releases/orst-sde031999.html

Status: Distribute freely with credit given to source

Date: March 25, 1999

Contact: Eric Sanford

sanforde@ava.bcc.orst.edu

541-737-5359

Oregon State University

Studies Document Ease Of Ecosystem Disruption

CORVALLIS, Ore. - Two new studies suggest that ecosystems can be

far more vulnerable than often assumed, subject to disruption by

fairly small environmental changes or loss of "minor" species not

traditionally thought to be important - and in considerable peril

from global change.

Both research efforts were done by ecologists from the Department

of Zoology at Oregon State University on the marine rocky

intertidal shores of the Oregon coast.

One report, to be published Friday in the journal Science,

indicates that some ecological impacts of global warming might

be abrupt, significant, and generally underestimated - not just

a slow shift of species from one region to another. It found that

small changes in ocean temperature could affect important or

"keystone" species and trigger large, relatively rapid changes

in intertidal ecology.

The other report, published today in the journal Nature, suggests

that measures to protect ecosystem health and function must

consider not only those keystone species known to play dominant

roles, but also many less prominent species which, at various

times, may actually be highly important.

Together, the research findings imply that the function of

complex ecosystems is both difficult to predict and sometimes

surprisingly easy to disrupt, especially with the advent of

human-related stresses such as over-exploitation, increased

species extinctions and climate change.

"As we consider the impacts of global warming, many people assume

the effects will be gradual, a shift to new regions by various

plant and animal species," said Eric Sanford, an OSU ecologist.

"But this study shows that if you have an important species which

is highly sensitive to temperature, then the effects of small

temperature changes on an ecosystem can be amplified by species

interactions."

In his research, Sanford looked at the ochre sea star, which

feeds on the California mussel and in the Pacific Northwest

intertidal ecosystem holds this dominant competitor in check. But

Sanford found that the rates of predation by this sea star are

very sensitive to small changes in water temperature associated

with episodes of wind-driven upwelling. It's one of the first

experiments of its type to document a direct link between small

temperature changes and the effects of a keystone species.

"Different species interact constantly through such mechanisms

as predation, competition and disease," Sanford said. "Because

of that, an impact on a keystone species may cascade through the

community and cause a relatively quick, system-wide impact."

The new study reported in Nature, on the other hand, looked not

so much at the keystone species of an ecosystem but the

comparatively minor species that often get ignored.

Its findings challenge some conventional wisdom about ecological

protection.

"Our tendency is to focus research and management efforts on

species that have consistent, dramatic impacts on an ecosystem,"

said Eric Berlow, a recent OSU doctoral graduate now doing

research at the University of California, Berkeley.

Underlying that approach is the assumption that by maintaining

populations of the species believed to be the most important, the

larger ecosystem will be protected and the lesser species can be

ignored - or even exploited - because they are of little

ecological significance.

Berlow's study challenges that thesis, and in the process makes

a strong case for the management and protection of whole

ecosystems, not individual species.

In his experiment, Berlow examined the dog whelk, a marine snail

that acts as a predator on mussels and barnacles. Unlike many

terrestrial predators, such as wolves and mountain lions, it is

easy to conduct experiments with rocky intertidal organisms,

Berlow said. In this case he manipulated whelk abundance to

compare the impacts of strong versus weak species effects.

While strong predation on mussels had a consistent effect under

all the conditions examined, the effects of weak predation were

highly variable. In individual situations, weak predation

actually had important effects on mussel abundance, but these

effects varied from place to place and time to time.

"The effects were visually dramatic," Berlow said. "Some weak

predation plots were dominated by mussels while others had none.

So even though the effects of weak predation by whelks 'averaged

out' to about zero, it would be a serious mistake to treat the

effects as minor or insignificant.

"Sometimes what we consider to be noise is in fact an important

part of the signal," Berlow said. "We just weren't listening

right, we haven't always measured the right things."

In a management context, Berlow said, the experiment makes a case

for managing whole ecosystems, since ecosystem health is likely

to depend on the interactions of many species, the abundant ones

as well as the rare ones, the keystones and the

"not-so-keystones."

And in efforts to better understand ecosystem function, he said,

researchers will have to begin paying far closer attention to

seemingly unimportant plant or animal species.

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By David Stauth, 541-737-0787 SOURCES: Eric Sanford, 541-737-5359

Eric Berlow, 510-643-5430

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