Rainforests: Lungs AND Heart of the Planet?
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New Scientists reports this month a possibly controversial finding that not only are rainforests giant carbon sinks of the planet (lungs), but they may also be responsible for moving (heart) many of the weather patterns we see all around the globe. This has impacts on the US, which may see more land turned to desert and see similar changes in Australia, which is already having a hard time with prolonged droughts.The new study suggests that rainforests (both in the Amazon and in tropical Africa) create winds that circulate water around the planet, thus explaining why far interiors of continents get just as much moisture and rainfall as coastal areas. Over half the rainfall in rainforests evaporates and recirculates, keeping the upper air moist. Findings now show that rainforests are also moving the air around them, thus also moving the water around.
How are Rainforests Creating Wind?
As water vapor around coastal forests condenses, it lowers area air pressure. This process is stronger over the forest than over the ocean, thus creating a wind which pushes the evaporated moisture inland. This process repeats itself as moisture is recycled, creating low pressure areas and thus winds moving the moisture further inland. How much moisture/water are we actually talking about? Well according to the article, "the Amazon rainforest...releases 20 trillion litres of moisture each day."
The two Russian scientists, (Anastassia Makarieva and Victor Gorshkov of the St Petersburg Nuclear Physics Institute) responsible for the theory are calling it the "Biotic Pump" and saying that while conventional meteorology states that winds are caused by changes in temperature of the atmosphere, their claim is that the changes in atmospheric moisture are just as large a driver. So large in fact that they are partly responsible for large changes like the trade winds, as well as local features like hurricanes.
Why Are Some Areas Turning to Desert?
The difference, the scientists say has to do with coastal forests. Areas that lack coastal forests to get the moisture circulating, have much drier interiors. Conversely, areas that have coastal forests get just as much moisture and rainfall inland. This is why the scientists say that the United States is headed towards desert, as coastal areas (temperate forest) are increasingly becoming deforested.
Many in the scientific community are not so sure. While they may agree that the principles behind the theory are accurate, they don't think that it would have as large an impact as the Russian scientists are claiming. Though more scientists are coming to their aid, stating that current theories don't explain much of what is seen in interior regions and even that this theory may "transform how we view forest loss, climate change, and hydrology."
Scientists already think that moisture from the Amazon is transported over to South Africa and the American Midwest. With this new theory, they have one more way to predict what a loss in rainforest would mean to global rainfall and water patterns. This may also explain how past civilizations, burning down forests, may have had a greater influence on the landscape and climate we see today.
The Future of the Rainforests
What does this mean for rainforests and how can we protect them? Scientists predict that if "the planet warms by 4 degrees, 85 percent of the forest could dry out and die," though they also say that minimal deforestation will be enough to turn the water pump off. So what do we do? Well, get our hands dirty and plant trees. Planted forests, once large enough, should be just as good as natural forests because either way the forests attract rain. Does this mean we can help restore moisture to other inland areas by planting and improving coastal forests? Makarieva and Gorshkov seem to think so. :New Scientist
More on Loss of Rainforests
Rainforests in Some Regions are Re-growing Rapidly: Should We Worry Anymore About Deforestation?
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Satellite Images Show Papua New Guinea's Rapid Deforestation
Is Deforestation the Solution to Climate Change?