Vines spread, choke trees in deepest Amazon jungle

Thursday, August 15, 2002
By Peter Graff, Reuters

LONDON - Jungle vines are spreading faster in South America's Amazon
rainforest than before, choking trees and potentially slowing the
forests' ability to soak up damaging greenhouse gases, scientists say.

The spread of woody vines - like the ones Tarzan swings from in the
movies - is the first change in plant composition that scientists
have recorded in the deepest virgin jungle and suggests humankind is
having more impact on delicate ecosystems than previously shown.

A team of researchers from Bolivia, Ecuador, Peru, and the United
States, led by Oliver Phillips of Leeds University in Britain,
counted and measured the vines, called lianas, in the primary
rainforests of the Amazon.

They found that the "dominance" of lianas over trees had increased by
between 1.7 and 4.6 per year over the last two decades of the 20th
century. "It's the first time that a changing composition has been
observed in mature forests," said Phillips. His team's findings are
to be published in the British science journal Nature on Thursday.

He said the growth in vines appeared to have been caused by greater
concentrations of carbon dioxide, the greenhouse gas that most
scientists believe is causing global temperatures to rise as a result
of human activity.

Plants absorb carbon dioxide in photosynthesis, and scientists have
predicted that as humans produce more of the gas, forests would grow
to soak some of it up, a phenomenon called the "carbon sink," which
could help ease global warming.

But Phillips said the additional carbon appears to benefit
resource-hungry vines more than slower-growing trees, throwing off
the balance in jungle forests. "What we think we were finding is the
ecosystem responding, not just in growth but in a change in its
composition. If you change an environmental driver like carbon
dioxide concentration, some plants will do better than others," he

As the vines weigh down trees and kill them, they can reduce the
ability of the forest to soak up more carbon, making the problem of
global warming even worse.

Other plant and animal species are also likely to have been affected
by the increase in vines relative to trees. Different insects may
pollinate vines rather than trees, different birds may eat the
insects, and so on. "The ecosystem's connected. You change one part,
and other parts are likely to change too," Phillips said. "It's a
kind of example of how we can't predict how the world is going to
respond to the changes we're causing."

Copyright 2002, Reuters
All Rights Reserved

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