Biggest trees face dire future

Big trees face a dire future due to the habitat fragmentation, selective harvesting by loggers, exotic invaders, and the effects of climate change.

Selective logging can be damaging in and of itself to forest ecology, but even more worrying for the authors is that logging in any form substantially increases the risk of complete forest clearing.

Clearing of previously logged forest is particularly acute in Indonesia, where palm oil producers and pulp and paper companies have converted vast swathes of land for plantations. The authors note that Indonesia's recent decision to exclude some 35 million hectares of logged-over secondary forest from their moratorium on new concessions for plantations was in part driven by accessibility granted by logging roads.

Logging is expected to figure prominently in a climate change mitigation measure known as reducing emissions from deforestation and degradation (REDD), which is currently under discussion in international climate talks. The concept originally aimed to fund relatively conventional forest conservation, but has since been expanded to REDD+ to include activities that degrade forests and therefore produce carbon dioxide. REDD+ may involve logging in two ways: providing funds to prevent it outright in a project area or acting as a form of subsidy to shift conventional logging practices toward less damaging ones.

Opportunities to directly tackle tropical forest logging, including bans on raw-log exports that have been adopted by many countries, reducing annual allowable cuts and extending rotation times, eliminating barriers to community ownership of forests through land tenure reform, cutting subsidies that favor industrial forestry, and establishing protected areas where logging is prohibited.

Reviewing research from forest around the world provides evidence of decline among the world’s “biggest and most magnificent” trees and details the range of the threats they face. Its demise will have substantial impacts on the biodiversity and forest ecology, while worsening climate change.

Giant trees offer critical habitat and forge for wildlife, while transpiring massive amount of water through their leaves, contributing to local rain fall. Old trees also lock up massive amounts of carbon.

The ability of big trees to sequester carbon and render other ecosystem service is threatened by human activities. Loggers particularly target some of the world’s largest trees. The oldest trees are the most valuable and therefore the first to be cut in the virgin forest areas.

Big trees are also sensitive to fragmentation, which exposes them to stronger winds and drier conditions. Its susceptibility seems counter-intuitive given big trees' life histories, which invariably include periods of drought and other stress.

Climate change is having less direct impacts on forests, including creating conditions for exotic pathogens to thrive.

"The decline of big trees foretells a different world where ancient behemoths are replaced by short-lived pioneers and generalists that can grow anywhere, where forests store less carbon and sustain fewer dependent animals, where giant cathedral-like crowns become a thing of the past." 

-  Paulo Anjelo J. Santos

Reference: http://www.cityjournal.in/Newspaper/20120211/Environment/Environment_2.html