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Global decline of big trees in old-growth forests worrying, argue scientists

The decline of large trees is putting biodiversity and forest health at risk globally, warn researchers writing in the journal Science.

In a commentary published Friday, December 7, David Lindenmayer, William Laurance, and Jerry Franklin argue that large trees typically found in old-growth forests play a critical ecological role, offering niche habitats for wildlife, storing large amounts of carbon, and providing abundant fruit, foliage, and flowers. But they note that a spate of studies suggest that big old trees are in decline in many ecosystems around the world: California has lost 95 percent of its redwoods, Swedish forests have experienced more than a 90 percent decline in large tree density, and fragmented Brazilian rainforests typically see a 50 percent die-off of big trees within 30 years of isolation.

Big Dipterocarp in the rainforest of Sumatra, Indonesia. Photo by Rhett A. Butler

Big trees are particularly targeted by loggers, but they are also exceptionally vulnerable to ecosystem change, including drought, increased incidence of wildfires, edge effects, and disease. These conditions can lead to elevated rates of mortality and reduced recruitment, with trickle-down effects for wildlife and plant communities, according to the authors.

Lindenmayer and colleagues say that the consequences of big tree decline are still poorly understood, necessitating more research.

“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 write. “Targeted research is needed to better understand their key threats and devise strategies to counter them. Without such initiatives, these iconic organisms and the many species dependent on them could be lost or greatly diminished.”

CITATION: David B. Lindenmayer, William F. Laurance, Jerry F. Franklin. Global Decline in Large Old Trees. Science 7 December 2012: Vol. 338 no. 6112 pp. 1305-1306 DOI: 10.1126/science.1231070

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