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Erosion and Flooding

image of flooding
Photo by Lynn Betts, USDA Natural Resources Conservation Service

Deforestation contributes to erosion by exposing soils to wind and rain.

When the ground surface is stripped of vegetation, the upper soils are vulnerable to both wind and water erosion.  Soil is washed into rivers when it rains, and then out to sea.  This destroys the ability for the land to regenerate because it has lost its topsoil.  It also destroys marine environments.  In several parts of the world, entire sections of countries have been rendered unproductive because of soil loss.

One of the world’s most serious erosion problems is in China.  From the Yellow River, over 1.6 billion tons of sediment flows into the ocean each year. The sediment comes mainly from water erosion in the Loess Plateau in the northwest of the country.

image of erosion
Photo by USDA Natural Resources Conservation Service

Erosion from deforestation is a problem in many other countries.  In the United States there have been significantly increased incidents of flooding over the past fifty years. Forests have a natural ability to absorb water when it rains, and to release that water slowly into rivers.  Following deforestation in a rainfall catchment area, the water moves more quickly from the land to the rivers, causing erosion and stripping the topsoil.  Because the rivers fill more quickly they are much more prone to flashfloods.  Floods that break the banks of the rivers then exacerbate the problem by changing the path of the river and causing additional severe erosion where the water now flows.

erosion flooding image
Photo by Tim McCabe, USDA Natural Resources Conservation Service

When we observe floods on television and see dirty brown water surging through a city or out to sea, it is more likely than not that severe erosion has occurred and that the flood was the result of deforestation.
By reforesting bare land, Wild Again restores natural water catchments and decreases the risks of floods, mudslides, and other forms of erosion.

Desertification

Desertification means means land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including deforestation.
Reforestation also helps to prevent desertification and can reverse desertification trends.

image of erosion

It is a common misconception that droughts cause desertification. In most cases the causes are social and economic, resulting from human intervention in the form of deforestation and over-exploitation of the land.  Typically this has involved overgrazing and felling of trees and brushwood for fuel.  Increased population and livestock pressure on marginal lands has accelerated desertification.  Droughts are common in arid and semiarid lands. Well-managed lands can recover from drought when the rains return. Continued land abuse during droughts, however, increases land degradation.

On the Southern edge of the Sahara, an area the size of Somalia has become desert over the past 50 years.  The same fate threatens more than one third of Africa.  Virtually all of the inhabited areas of Africa are prone to soil and environmental degradation in one form or another. Most regions of the continent suffer from several forms of environmental degradation, leading to desertification and with its detrimental impact on food and agricultural productivity and production. The process is often not obvious because it is usually gradual and unnoticeable.

The United Nations believes that reforestation is an effective method for repairing degraded lands and reversing the trend of desertification.  In areas with more than 300 mm of rainfall per year for example, dry reforestation can be effective when the plantation site is wisely chosen and stream water collection techniques are applied. Below 300 mm per year, extra watering is required according to the particular features of the intervention area.


International sites

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image of flooding

Photo by Lynn Betts, USDA Natural Resources Conservation Service

click here to visit the Prince's Rainforests Project website