World's Big Trees Are Dying

http://www.sciencedaily.com/releases/2012/12/121206162519.htm

ScienceDaily (Dec. 6, 2012) — The largest living organisms on the planet, the big, old trees that harbour and sustain countless birds and other wildlife, are dying.

A report by three of the world's leading ecologists in today's issue of the journal Science warns of an alarming increase in deathrates among trees 100-300 years old in many of the world's forests, woodlands, savannahs, 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 Centre 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," he and colleagues Professor Bill Laurance of James Cook University, Australia, and Professor Jerry Franklin of Washington University, USA, say in their Science report.

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Prof. 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 savannahs, 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.

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"Large old trees play critical ecological roles. They provide nesting or sheltering cavities for up to 30% of all birds and animals in some ecosystems. They store huge amounts of carbon. They recycle soil nutrients, create rich patches for other life to thrive in, and influence the flow of water within landscapes and the local climate.

"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.

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