Karela Fry

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The many balances of nature

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Nature reports:

Could you prevent nine local extinctions by hastening one extinction? It sounds completely counterintuitive, but a pair of ecosystem modellers are proposing that conservationists could sometimes prop up a troubled ecosystem by removing one or more of its species — and using models to determine the timing and order of those removals.

The species that make up an ecosystem are connected in complex ‘food webs’ of eater and eaten. When one species disappears, its predators can no longer eat it and its prey are no longer eaten by it. Changes in these populations affect others. Such impact ‘cascades’ can be unpredictable and sometimes catastrophic.

Sagar Sahasrabudhe and Adilson Motter of Northwestern University in Evanston, Illinois, have shown that in several model food webs, as well as in two webs modelled with data derived from real ecosystems — the Chesapeake Bay off Maryland and Virginia and the Coachella Valley in Southern California — removing or partially suppressing one or more species at key time points after one member has gone extinct saves other members of the web from local extinction.

The idea relies on the fact that ecosystem networks can often shift to a different stable arrangement after losing members. “Ecological systems are quite robust, actually,” says Motter. The famous “balance of nature” is perhaps better understood as the “multiple possible balances of nature”. But the order of removals matters.

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Written by Arhopala Bazaloides

January 27, 2011 at 4:23 am

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