The vast areas of tropical forest in the Amazon and in Africa may be even more important to the health of the Earth than previously thought.

According to some controversial new research, these vast rainforest help to generate wind and pump water around the planet. The theory helps explain how Australia turned from deep forest into desert and also explains why continents with forests at their hearts receive the same amount of rainfall as the coastlines. The theory also suggests that even without global warming, North America has the potential to turn into one large desert.

The importance of trees and forest in the rain cycle has been known for a long time. Up to half the rain which falls on a tropical rainforest will evaporate or transpire from the trees keeping the air above the forest nice and moist. Ocean winds can then pick up and spread the moisture in the air and this in turn creates more rainfall.

However Victor Gorschkov and Anastassia Makarieca of the St Petersburg Nuclear Physics Institute in Russia claim that the forests themselves may actually create some of these winds. Their theory is that evaporation is stronger over the trees than it is over the oceans. This means that the pressure over the forests will also be lower and this pulls in the air from the higher pressure regions over oceans and seas. This pulling action creates a wind which helps to drive the moist air away from the oceans and coastlines into the forests, thus helping to create rainfall on the inner sections of continents.

The Russian pair looked at several regions with and without inland rainforests to back up their ideas and have seen results which show that with large inland rainforests, the rainfall is approximately equal in the forest to the coast however areas without the forests have significantly more rainfall at the coastline than inland.

These findings, if true, provide even more stark evidence that rainforests are crucial to the Earth’s climate. Most worryingly is the deforestation of North America. The US, until recently, has always contained large swathes of forest however with increasing deforestation happening, the pair claim that North America may soon find itself turning into a large desert.

The research has caused much debate in the scientific community with many writing the pair’s findings off, claiming that although deforestation has some small effect on rainfall, the effect is not as significant as the Russian pair claim. Others hail their findings as crucial to understanding the global impact of deforestation.

The one positive in the research is that the damage done to the rainfall patterns is entirely reversible – by replanting the forests, the rain cycle will be kick started once more and over time, the cycle will go back to how it was before.

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