02/02/02 -- Biodiversity Required to Sustain Ecosystems

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FOREST CONSERVATION NEWS TODAY

Biodiversity Required to Sustain Ecosystems

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February 2, 2002

OVERVIEW & COMMENTARY by Forests.org

Important new scientific studies are investigating links between

species diversity and well-being of ecosystems. This research is

beginning to make clear the horrific ecocidal implications for

Planetary sustainability of the current human-induced hemorrhaging of

global biodiversity. The health of an ecosystem depends upon the

variety of species that inhabit it. When the diversity of species in

an ecosystem decreases, the ecosystem becomes less productive. Global

species loss thus threatens the ecological integrity of local,

regional and ultimately global ecosystems. Only so much can be lost,

and then the condition of ecosystems inexorably descends further,

ultimately collapsing. We cannot expect the biosphere to just bounce

back from our ecologically diminishing activities. With every species

lost; future human, ecological and development potential is limited

essentially forever.

g.b.

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ITEM #1

Title: Variety of Species Best for Ecosystems

Date: January 30, 2002

Byline: Cat Lazaroff

By COLLEGE PARK, Maryland, January 30, 2002 (ENS) - The health of an

ecosystem depends on the variety of species that inhabit it, suggests

new research from the University of Maryland. The researchers say the

discovery could revolutionize how scientists look at the effects of

species extinction.

In a paper published in the January 24 issue of the journal "Nature,"

University of Maryland biology professor Margaret Palmer and doctoral

student Bradley Cardinale show that when several species of caddisfly

larvae live together in a stream, they get more food from the stream

and, as a result, are likely to be more productive than when only a

single species inhabits the same area.

The study is one of the first to look at aquatic species in the

growing controversy over biodiversity loss and the potential

importance of conserving different species in an ecosystem.

"Our research supports findings from other studies that show when you

decrease the diversity of species in an ecosystem, the ecosystem

becomes less productive," said Palmer. "What's really exciting about

our work is that we were able to show why this happens. We found that

species sometimes help each other capture food. When you lose a

species, the others may eat less and become less productive."

The lifestyle of the caddisfly, an insect found in streams around the

world and replicated by fly fishermen in fishing lures, lends itself

well to this type of study. The larvae live in little cases attached

to rocks, and build silk nets to capture and filter food from the

water.

The larvae are large enough, at up to three quarters of an inch long,

that they can be dissected and examined to see how much food ends up

in their guts.

Palmer and Cardinale, along with adjunct faculty member Scott Collins,

gathered caddisfly larvae from natural streams and put them in streams

they had constructed in the lab, where they could control the

environment. In some of the lab streams, they put only a single

species. In other streams, they combined several species.

"The pattern of water flow around the caddisflies totally changed when

we mixed the species," said Palmer. "Water flow was faster, and more

food particles were delivered to the larval capture nets than in the

single species streams."

"It appears that placing species together, each with a different size

filtration net, created a form of physical complexity that altered the

flow of water near the stream bed and allowed the whole community to

capture more food," explained Cardinale.

"When species help each other capture food, it is an interaction

ecologists call facilitation," said Palmer. "We found that increasing

the diversity of species in a stream increases the likelihood of

facilitation. Studies with plants have suggested this happens, but

because it's much harder to measure food capture in a plant, research

has been unable to prove it. Based on our results, we can now

hypothesize that in any ecosystem where food is delivered passively,

such as by wind or water, facilitative interactions that are

maintained by a high species diversity could cause that ecosystem to

perform better."

The team's findings raise new concerns about the ecological

consequences of species extinction.

"Between 17 and 50 percent of the species now on the planet are

predicted to be lost as a result of human activities," Cardinale said.

"Our study shows that ecosystems with more species are more efficient

and that as species vanish, the ecosystems we rely on soheavily will

become less productive."

ITEM #2

Title: Biodiversity May Need Millions of Years to Recover

Date: January 3, 2002

Byline: Cat Lazaroff

BERKELEY, California, January 3, 2002 (ENS) - The worldwide decimation

of wildlife by humans could be "permanent on multi-million year

timescales," warns James Kirchner of the University of California at

Berkeley. Kirchner's analysis of long term trends in the fossil record

suggests that natural speed limits constrain how quickly biodiversity

can rebound after waves of extinction.

Over the last 500 million years, life on Earth has experienced a

series of booms and busts. The busts, or mass extinctions, can be

gradual, occurring over thousands or millions of years, or they can

happen suddenly in response to a natural catastrophe.

But the booms of diversification, in which hundreds or thousands of

new organisms appear, rarely happen quickly, writes Kirchner in this

week's issue of the journal "Nature."

His statistical analysis of the rates of extinction and

diversification in the fossil record shows that life seldom rebounds

rapidly after an extinction.

The results imply that the diversification of life obeys so called

speed limits set by evolutionary processes, said Kirchner, a professor

of earth and planetary science at UC Berkeley.

"There seem to be biological mechanisms that limit diversification of

new organisms and control which ones become successful enough to

persist," he said. "Biodiversity is slow to recover after an

extinction."

This apparent speed limit on the rate at which surviving organisms

evolve and diversify has major implications for present day

extinctions - caused not by natural catastrophes but by human sources

such as pollution, alteration of natural habitats, and unsustainable

hunting and fishing.

"If we substantially diminish biodiversity on Earth, we can't expect

the biosphere to just bounce back. It doesn't do that. The process of

diversification is too slow," Kirchner said. "The planet would be

biologically depleted for millions of years, with consequences

extending not only beyond the lives of our children's children, but

beyond the likely lifespan of the entire human species."

Kirchner has been mining a fossil database created by the late

University of Chicago paleontologist Jack Sepkoski, who catalogued the

genera and families of fossil marine animals over the past 530 million

years, from the Cambrian to the present. Using a technique called

spectral analysis, Kirchner looked for patterns in the rates at which

new organisms appear or disappear.

Last year, Kirchner and colleague Anne Weil reported that the Earth

needs, on average, about 10 million years to recover from global

extinctions, whether they involve the loss of most life on Earth or

wipe out far fewer species. This was much longer than most scientists

had believed.

The new results come from asking a related question: How do rates of

extinction and diversification vary, and how are they related? This is

important because, if rapid diversification is possible, biodiversity

might be able to rebound quickly from a global extinction.

Kirchner's analysis found that extinction rates and diversification

rates are about equally variable over long spans of geological time.

Over shorter periods, however, diversification rates vary much less

than extinction rates do.

That means that evolution does not accelerate quickly in response to

rapid bursts of extinction.

One possible explanation for why diversification takes so long to

speed up after an extinction is that extinction eliminates not merely

species or groups of species, but removes ecological niches: the roles

which organisms play within ecosystems.

Recovery becomes more complicated because specialized roles, such as

parasites that live on just one species, or animals that consume just

one kind of food, do not evolve until their hosts are already well

established.

"This shows that extinction is not like knocking chess pieces off a

chessboard, with the empty squares ready for you to plunk down new

pieces," Kirchner said. "Extinction is more like knocking down a house

of cards. You only have places to put new cards as you rebuild the

structure of the house."

"For a new kind of organism to evolve and survive long enough for us

to notice it - for it to become common enough to leave a fossil record

- requires that it have an evolutionary niche," he explained.

"The organism has to have some role in order to succeed in its

ecosystem. As a result, the ecosystem must first increase in

complexity so there are niches for new organisms to fill, which is

probably a very complicated process.

"At a fundamental biological level it takes time to build niches,

evolve new organisms and filter out unsuccessful ones, although it's

not yet clear what all the limiting factors are."

Kirchner's work was supported by grants from the National Science

Foundation and the University of California.

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