LOCAL AND NATIONAL CONSEQUENCES

LOSS OF LOCAL CLIMATE REGULATION

The local level is where deforestation has had and will have the most immediate effect. With forest loss, the local community loses the system that performed valuable but unnoticed services like ensuring the regular flow of clean water and protecting the community from flood and drought. The forest acts as a sort of sponge, soaking up the tremendous amounts of rainfall brought by tropical downpours, and releasing water at regular intervals. This regulating feature of tropical rainforests prevents destructive flood and drought cycles. However, when forest cover is lost, runoff rapidly flows into streams, elevating river levels and subjecting downstream villages, cities, and agricultural fields to sudden and severe flooding especially during the rainy season. During the dry season, such areas downstream of deforestation are prone to months-long droughts which interrupt river navigation, wreak havoc on crops, and disrupt industrial operations.

Hurricane Mitch

Situated on steep slops, montane and watershed forests are especially important in ensuring water flow and inhibiting erosion, yet during the 1980's, montane formations suffered the highest deforestation rate of tropical forests.

Additionally, the forest adds to local humidity through transpiration (the process by which plants release water through their leaves), and thus adds to local rainfall. For example, 50-80% of the moisture in the central and western Amazon remains in the ecosystem water cycle. In the water cycle, moisture is transpired and evaporated into the atmosphere forming rain clouds before being precipitated as rain back onto the forest. When the forests are cut down, less moisture is evapotranspired into the atmosphere resulting in the formation of fewer rain clouds. Subsequently there is a decline in rainfall, subjecting the area to drought. If rains stop falling, within a few years the area can become arid with the strong tropical sun baking down on the scrub-land. Today Madagascar is largely a red, treeless desert from generations of severe deforestation. River flows decline and smaller amounts of quality water reaches cities and agricultural lands. The declining rainfall in interior West African countries has in part been attributed to excessive clearing of the coastal rainforests. Similarly, new research in Australia suggest that if it were not for human influences - specifically widespread agricultural fires - the dry outback might be a wetter more hospitable place than it is today. The effect of vegetation change from forests that favor rainfall to grassland and bush can impact precipitation patterns. Colombia, once second in the world with freshwater reserves, has fallen to 24th due to its extensive deforestation over the past 30 years. Excessive deforestation around the Malaysian capital of Kuala Lampur, combined with the dry conditions created by el Niño, triggered strict water rationing in 1998 and for the first time the city had to import water.

There is serious concern that widespread deforestation could lead to a significant decline in rainfall and could trigger a positive-feedback process of increasing dessication for neighboring forest cover, reducing its moisture stocks and its vegetation, furthering the dessication effect for the region. Eventually the effect could extend outside the region, affecting important agricultural zones and other watersheds. At the 1998 global climate treaty conference in Buenos Aires, Britain, citing a disturbing study at the Institute of Ecology in Edinburgh, suggested the Amazon rainforest could be lost in 50 years due to shifts in rainfall patterns induced by global warming and land conversion.

The newly dessicated forest becomes prone to devastating fires. Such fires materialized in 1997 and 1998 in conjunction with the dry conditions created by el Niño. Millions of acres burned as fires swept through Indonesia, Brazil, Colombia, Central America, Florida, and other countries. The Woods Hole Research Center warned that more than 400,00 square kilometers of Brazilian Amazonia were highly vulnerable to fire in 1998 (Woods Hole Research Center 1998).