Giant Trees Are Dying, Experts Say
The largest living organisms on the planet, the big, old trees that harbor and sustain countless birds and other wildlife, are dying.
AsianScientist (Dec. 10, 2012) – The largest living organisms on the planet, the big, old trees that harbor and sustain countless birds and other wildlife, are dying.
A report by three ecologists in this week’s issue of the journal Science warns of an alarming increase in death rates among century-old trees in many of the world’s forests, woodlands, savannas, farming areas, and even in cities.
“It’s a worldwide problem and appears to be happening in most types of forest,” says lead author Professor David Lindenmayer of the ARC Center of Excellence for Environmental Decisions (CEED) and Australian National University.
“Large old trees are critical in many natural and human-dominated environments. Studies of ecosystems around the world suggest populations of these trees are declining rapidly,” the authors write in their report.
“Research is urgently needed to identify the causes of rapid losses of large old trees and strategies for improved management. Without… policy changes, large old trees will diminish or disappear in many ecosystems, leading to losses of their associated biota and ecosystem functions.”
Lindenmayer says they were first tipped off to the loss of big old trees while examining Swedish forestry records going back to the 1860s.
Then a 30-year study of Mountain Ash (Eucalyptus regnans) forest in Australia confirmed not only that big old trees were dying en masse in forest fires, but also perishing at ten times the normal rate in non-fire years – apparently due to drought, high temperatures, logging, and other causes.
Looking round the world, the scientists found similar trends at all latitudes, in California’s Yosemite National Park, on the African savannas, in the rainforests of Brazil, the temperate forests of Europe and the boreal forests of the far north.
Losses of large trees were also pronounced in agricultural landscapes and even cities, where people make efforts to preserve them.
“It is a very, very disturbing trend. We are talking about the loss of the biggest living organisms on the planet, of the largest flowering plants on the planet, of organisms that play a key role in regulating and enriching our world,” says Professor Bill Laurance of James Cook University.
Large old trees play critical ecological roles, says Laurance. They provide nesting or sheltering cavities for up to 30 percent of all birds and animals in some ecosystems, store huge amounts of carbon, and recycle soil nutrients, he explains.
“Big trees supply abundant food for numerous animals in the form of fruits, flowers, foliage, and nectar. Their hollows offer nests and shelter for birds and animals like Australia’s endangered Leadbeater’s Possum (Gymnobelideus leadbeateri) – and their loss could mean extinction for such creatures,” he says.
The alarming decline in old trees in so many types of forest appears to be driven by a combination of forces, including land clearing, agricultural practices, man-made changes in fire regimes, logging and timber gathering, insect attack, and rapid climatic changes.
The researchers liken the global loss of big trees to the tragedy that has already befallen the world’s largest mammals, such as elephants, rhinos, tigers, and whales, cautioning that almost nowhere do conservation programs have the time-frames lasting centuries, which are needed to assure the survival of old trees.
“Just as large-bodied animals such as elephants, tigers, and cetaceans have declined drastically in many parts of the world, a growing body of evidence suggests that large old trees could be equally imperiled,” they warn.
They call for an urgent world-wide investigation to assess the extent of big tree loss, and to identify areas where big trees have a better chance of survival.
The article can be found at: Lindenmayer DB et al. (2012) Global Decline in Large Old Trees.
Source: ARC CEED.
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