January 27, 2012

Worlds Largest Trees Face Decline

According to long-term studies in Amazonia, Africa and central America, the worlds largest trees are dying off due to the encroachment of man. The roads and villages that men build fragment forests while the trees are battling against severe droughts, pests and diseases.

The studies have shown that the trees have adapted well to centuries of storms, pests and short-term climactic extremes, reports the Guardian. But these large trees are counterintuitively more vulnerable than other trees to modern threats.

William Laurance, a research professor at James Cook University in Cairns, Australia says, “Fragmentation of the forests is now disproportionately affecting the big trees. Not only do many more trees die near forest edges, but a higher proportion of the trees dying were the big trees. Their tall stature and relatively thick, inflexible trunks, may make them especially prone to uprooting and breakage near forest edges where wind turbulence is increased.”

The biggest trees are the most important trees in the forest. They comprise about 2 percent of the trees in a forest, but due to their size they contain 25 percent of the total biomass and seed large areas.

Big trees around the world are dying off for various reasons. Laurance reports about a Southern Indian shrub that invades the understory of the forest and prevents the seedlings from dropping onto the forest floor. These trees are in danger of disappearing because there are no big trees sprouting up to replace them.

Not only are the biggest trees in forests dying off, but the biggest trees in communities are dying. According to The Guardian, Dutch elm disease killed off the stateliest trees in Britain in the 1960´s and 1970´s. And new pests and diseases are being introduced to trees from the local garden centers killing off oak, ash and other species.

In tropical areas the largest trees are dying off due to droughts brought on by climate change. Laurance mentions studies in Puerto Rico and Costa Rica where the big trees suffer more than other organisms.

Laurance says, “In rainforests droughts promote surface fires that burn through leaf litter on the forest floor. Larger trees were initially thought to survive these fires but in fact many die two the three years later.”

The danger from not having big trees in the forests, according to Laurance, is that as the trees die off the forest releases more carbon into the atmosphere. Thus increasing the rate of climate change prompting more warming and more forest shrinkage.

The biggest trees are usually the oldest trees and host many inhabitants of the forest. Amazonian trees are often 400-1,400 years old, giant redwoods exceed 2,000 years old and giant sequoias 3,000 years old.


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