Temps de lecture :2 minutes
While forests, which store large quantities of carbon dioxide, are an important ally in the fight against climate change, they have already begun to be affected by it. Some of the effects are positive: with shorter winters, trees grow for longer periods, and with more CO2 in the air they grow faster, because the gas increases photosynthesis. Since the early 20th century, forest productivity has grown by around 40% in Europe.
Climate change is also modifying global forest distribution. The distribution of plant species depends to a large extent on temperature and rainfall, and forest species are tending to move towards higher latitudes and altitudes.
But these movements can have negative consequences. First, because some species are unable to adapt and will disappear. Second, because trees aren’t the only organisms that are migrating; pests are too. The larvae of the pine processionary moth and the mountain pine beetle – which destroys millions of hectares every year in western Canada – both benefit from global warming.
Extreme climate phenomena, such as drought, storms and flooding, are on the increase and also cause damage to the forest cover. Higher temperatures and plant decay cause vegetation to be drier and more flammable, leading to more frequent and intense wildfires in zones that are already vulnerable to fire.
Ultimately, the combined effects of global warming will make forests more fragile. An illustration of this phenomenon is the ‘drunken forest’. In Siberia, rising temperatures have resulted in the thawing of permafrost (soil that is usually frozen year round). As the soil softens, the trees wind up tilting over, growing in unusual directions. Because they are less solidly anchored in the ground, they are prone to collapse at the least disturbance, like a house of cards.