Trees and Forest Fires
Removal of the forests is the second most powerful source of CO2. It is responsible for 25% of all carbon emissions through burning and logging 35 million acres of trees each year - an area equivalent to the size of Italy.
In the 1990s the higher levels of CO2 was stimulating trees to grow. Computer models of climate change assumed that forests could absorb 3 billion tons of carbon annually, even without new planting.
This happy scenario is now known to be false. When plants come under stress the sugars they make during photosynthesis releases CO2 back into the air. This begins as temperatures rise so the forests are no longer a "sink".
In some areas trees are now becoming a source of atmospheric carbon dioxide.
When temperature rises above 1°C this will become a serous tipping point.
There will then be less and less benefit in planting trees.
This end the entire Kyoto campaign for offsetting carbon use against new planting. If we let temperatures go above one degree the benefit of planting trees decreases. We can no longer continue to emit carbon on the happy assumption that planting will make it OK.
During the recent heat waves European corn yields dropped 36%, oaks and pines grew more slowly. The hotter we get the less food we produce and the less carbon we sequest.
Ecosystems can withstand a rise of only 0.05°C per decade. We heating the planet by more than three times that. Trees cannot shift habitat and move like Ents into new ground.
Extra heat stresses most temperate forests, and changes the pattern of insects. For example, the spruce bark and mountain pine beetles in North America that were once kept in check by the cold, are now destroying vast areas of forest. This discharges more CO2.
In Siberia spring is arriving almost a month earlier, and this triggers plagues of moths that can eat the needles of an entire region. The trees die and then succumb to forest fires that in turn destroy soil vegetation and accelerate the melting of permafrost. The forests of Siberia are losing 10 million acres per year, while the Amazon tropical forests are on the edge of massive annihilation.
would A recent study of the three major tropical forests (map, left) found that deforestation in the Amazon would reduce rainfall significantly from Mexico to Texas during spring and summer when water is crucial for agriculture. Similarly, deforesting the Congo would reduce rain in the US Midwest, while in SE it affects China and the Balkans.
One of the first indicators of climate change has been that since the 1980s spring flowers have been opening earlier. There is a strong connection between earlier spring and the frequency of large forest fires.
During the 1997-98 El Nino 20M hectares burnt. This one event released 2.6 billion tons of carbon - the highest annual increase since measurements began. They were so massive that the output of CO2 from combustion reached 40% of the world total. This is happening again in 2006.
Indonesian fires have shown us that catastrophic events in small areas can release vast amounts that have been locked away for millennia.
There has been a four-fold jump in the average number of wildfires beginning, a process that began in the mid-1980s. The total area being burned is six and a half times greater, and the length of the bush fire season has been extended by 75 percent. In South-East Asia, in Russia and in the Amazon the extent of bush fires has increased.To the top