-Le rôle des forêts dans le cycle climatique

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climat et foret role liaisons interactions

The Earth’s forests help to maintain our atmosphere. Firstly, because they recycle much of the oxygen that we breathe (the phytoplankton in the oceans does the same) as a result of photosynthesis. Secondly, because they absorb large quantities of water (several hundred liters per day in the case of a tropical tree), which they release into the atmosphere through a process known as transpiration, and in so doing contribute to the humidity in the air and to precipitation. And, finally, because they trap significant quantities of CO2, which is transformed into organic matter such as starch in plants and lignin in trees by means of photosynthesis.

What is the scale of this phenomenon? Forest ecosystems store more than half the carbon accumulated by terrestrial ecosystems; the figure for 2005 was 638 billion tons, according to the FAO, which is more than all the carbon in the atmosphere. But this stockpile is declining. This is logical since the surface area of our forests is dwindling as a result of deforestation—itself a potent source of CO2 emissions.

Each year, the world’s forests continue to stockpile more carbon than they release. The surplus is still in the region of 0.7 billion tons a year. But the role they play as a carbon sink is increasingly endangered. So, what are we to do? The logical solution is to leave this carbon store well alone and to suspend the destruction of primary forests across the globe. The international community is currently discussing the possibility of introducing a compensation mechanism for countries that avoid destroying their forests and maintain them in good condition. Such a system would be difficult to put in place, but the World Bank, with the support of the United Nations, has already set up a fund that prefigures a system for financing avoidance of deforestation. The aim is also to show the communities that live in or near forested areas that the use of renewable sources such as fruit, nuts, and essential oils can be financially more rewarding than cutting down trees or converting forests into fields and grazing lands.

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