Extreme weather events and intensified fires already affecting forests
One consequence of climate change that affects forests is an increase in extreme weather events, which can cause significant tree loss. The value of trees damaged by 2004's Hurricane Ivan is estimated in the hundreds of millions of dollars in just the 12 hardest-hit U.S. counties alone (counties are mid-sized administrative regions, smaller than states).
Aside from such direct impacts, floods and storms can also alter water flows on which trees depend, hurting forest health.
A changed climate also opens the way for non-native, harmful species to invade disturbed ecosystems. Changes in temperature and rainfall can favour outbreaks of insect infestations, both in northern boreal forests and in temperate and tropical timber plantations, with devastating consequences.
Forest fires aggravated by warmer temperatures
Such anticipated changes in the ranges of tree species, in forest composition and in the size and occurrence of insect populations will also affect the dynamics of forest fires.
Although forest fires are mostly caused by humans, their growing frequency may be due to warmer temperatures and shifting winds resulting from climate change.
Certainly, regional droughts seem to have a clear link with the frequency and intensity of fires. In Portugal in 2003, nearly 400 000 hectares of forest were burnt during a scorching summer heat wave, the largest forest area burnt during a single year in Portugal’s entire history.
Helping forests cope
"Forest managers should assess the vulnerability of their forests and examine whether tree species already react sensitively towards extreme weather patterns,” according to Dieter Schoene, an FAO forest and climate change expert.
"Forest managers need to start looking at measures that can help forests cope with, and adapt to, climate change," he says, "or forests will not survive in the long term."
In developing countries, forest vulnerability assessments can be undertaken under the National Adaptation Programme of Action initiated by the United Nations Framework Convention on Climate Change.
This programme involves helping poor countries identify priority actions that need to be taken in order to adapt to the adverse effects of climate change.
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