How the pressure on tropical forests threatens rain

tropical forestA recent study conducted jointly by two leading universities in the United Kingdom, has revealed startling developments regarding the world’s tropics, and the even dire effects on the future of rainfall. The study has revealed that air passing over tropical areas, actually produces twice as much rain as air passing over areas with little to no vegetation. The positive effects that tropical forests have on rainfall, stretches for miles in some cases.

The scholars were able to extrapolate that deforestation would reduce the rain all over the Amazon in Brazil, by 20 percent. To reach this conclusion, they combined empirical data with future projections of forest loss. The study and its startling conclusions are published in Nature. One of the team-leaders in the study was shocked, to discover that this phenomenon is happening over the majority of the tropics. In particular, the researchers found that the Congo and Amazon forests were responsible for most of the rainfall over adjacent areas. The areas mentioned are heavily populated and the livelihood of many people depends on good rainfall.

The message is clear; the study shows unequivocally, that the continuing deforestation of the tropics would have tragic results for people miles away. Neighboring countries could be affected. This study brings to a rest, centuries old debate on whether vegetation has a bearing on rainfall or not. It has been known that plants lose moisture back into the air through evaporation. What was in dispute was the amount of moisture thus lost, and whether it could affect rainfall in any way. There were no conclusive answers, until now. There has been some evidence that forests contribute a great deal to atmospheric moisture, but the evidence was not conclusive, until now.

The exercise was a thorough affair, with equipment from NASA for monitoring rain and vegetation. NASA also provided a model to predict the flow of wind in the atmosphere, as well as the exploration on tropical rain forests. The teams observed the rain events of previous days, as well as the direction and distance the rain had covered. The scientists studied the rainfall in detail, measuring the amount of leaf water as well as moisture level in the atmosphere. By so doing, they were able to determine with accuracy, the amount of vegetation when the rain fell. The in-depth study brought the scientists to the conclusion that the air carried significantly more rain when it had passed more vegetation.

The co-team leader from the University of Leeds, Dr Stephen Arnold, explained further the methodology: They had to account for the exact interaction of air with vegetation over an area spanning thousands of miles. That was the only way they could understand the impact of the tropical forests on rain. The newly-released study has presented policy makers with a new mandate, namely, to determine how they are going to deal with deforestation and its devastating impact on rainfall. These effects are likely to fall on entire continents.

Dr Spracklen, the other team leader for the study, stated the need to embark upon initiatives aimed at saving the tropics. As an example, he pointed out that the government of Brazil had embarked, with some success, on a campaign to curb the high rate deforestation in their country. He pointed out that it is the only way of avoiding the threat to rainfall from deforestation. He pointed out that the Amazon in Brazil is responsible for most of the rainfall in that country, while the Congo basin is also responsible for most of the rain in Southern Africa. If the forests were to perish, drought would engulf these areas, known mostly for subsistence farming. The results would be devastating, the NERC-funded study concludes.

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