World’s largest and oldest trees are threatened

Posted by Flora Malein

Large, old trees are in rapid decline and need to be protected says a new study in the journal Science.

Large tree species play an important role in the healthy-functioning of ecosystems all over the globe and losing them puts many other plant and animal at risk suggests the study.

Professor David Lindenmayer from the Australian National University, Canberra, looked at ecosystems from many parts of the world which are home to large and old tree species. He found that these species are particularly vulnerable to human activities such as logging and land clearance leading to their decline in ecosystems at all latitutdes. For example, over 95% of California’s majestic coastal redwoods, which are among the tallest trees in the world, have been lost to logging and forest clearing.

"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 imperilled," says Professor Lindenmayer.

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

Large, old tree species provide many unique and specialist functions in ecosystems that simply cannot be fulfilled by younger and smaller individuals. The Mountain Ash tree (Eucalyptus regnans) in mainland Australia has a unique role in forests as home to more than 40 species of animals. Lindenmayer suggests that it is mainly human activities that are responsible for the loss of these species:

"In agricultural landscapes, for example, chronic livestock over-grazing, excessive nutrients from fertilizers, and deliberate removal for firewood and land clearing combine to severely reduce large old trees," he says.

"If we are to ensure the perpetual supply of large old trees, policies and management practices must be put in place that intentionally grow such trees and reduce their mortality rates."