- What is erosion? How does it start? What problems does it cause? Get the full story from Wikipedia
- Images of erosion following deforestation in Madagascar [wildmadagascar.org]
Forest conversion, agriculture and soil erosion
More on erosion
More calamities after the forests are gone
Damage to areas that are cleared of forests and replaced with plantations continues long after the trees are gone.
Erosion is one of the symptoms that commonly appear following conversion of forests to agricultural land – carrying away fertile soil, pesticides and the sources of livelihood for humans and wildlife.What is erosion?
When forests are cleared, the exposed topsoil often begins to erode, increasing sedimentation into watercourses (e.g. rivers). Things get worse if there are no forests left along the banks of rivers and other watercourses to keep soil carried by rain.1 Coffee, cassava, cotton, corn, palm oil, rice, sorghum, soybean, tea, tobacco, wheat are some of the crops whose cultivation cause soil erosion.2In soy production, lack of soil cover and exposure to the wind causes erosion and infertile soils. This is how every year, Brazil loses 55 million tons of topsoil.a
Impacts of erosion
Increased soil erosion, along with the growing use of agrochemicals, are causing serious damage to rivers that are used by forest communities, as well as plants and animals these communities depend on.- Impact on wildlife: Rainwater runoff carries pesticides, which are then found in the soil, water, sediment, and fish in areas adjacent to banana plantations. For example, Indians living in Xingu Indigenous Park in Brazil report declines in fish numbers. This trend is attributed to changes in the courses of waterways resulting from farming-related erosion and the silt deposition this causes.3
- Impact on ecosystems: As a result from erosion, pesticides are carried away by the rain to the coast. In Central America, plantation soil run-off ends up in the sea, where it affects the Meso American Reef.
- Flooding: In banana plantations, flooding occurs partly because of deforestation (soil is no longer there to absorb the water) and partly because of poorly constructed plantation drainage systems.
From savanna to desert: a ‘how-to’ guide
In the Brazilian cerrado, the combined effects of deforestation and increased soil temperatures have made it difficult for rainwater to sink into the soil.
When plantation areas of up to 10,000 hectares are exposed following deforestation, the soil becomes extremely vulnerable to wind and water erosion. As a result, desertification has become a serious threat to these areas, which experience long dry season.
In the Santarem region, intensive rainfall causes erosion, especially near streams and rivers. The sediment is transported downstream, where it makes the rivers and coves turbid.4
© World Resources Institute 2000
Forest areas converted globally (until 2000). Click to expand.
What is the scale of the erosion problem?
It is estimated that since 1960, one-third of the world’s arable land has been lost through erosion and other degradations. The problem persists, with a reported loss rate of about 10 million hectares per year.In reality, the situation may be much more worrying. Over the last 5 decades, increases in agricultural productivity have made it possible to produce more crops on the same amount of land.
But the problem is that because agricultural land is often degraded and almost useless, producers keep on moving to more productive land. Globally, the land used and abandoned in the last 50 years may be equal to the amount of land used today.5
1 Centre for Science in the Public Interest. 2005. Cruel Oil: How palm oil harms health, rainforests and wildlife. Report. 48 pp.
2 Carey C., Oettli D. 2006. Determining links between agricultural crop expansion and deforestation. A report prepared for the WWF Forest Conversion Initiative. 71 pp.
3 Van Gelder J.W., Dros J.M. 2006. From rainforest to chicken breast: Effects of soybean cultivation for animal feed on people and nature in the Amazon region - a chain of custody study. Report. 47 pp.
4 Greenpeace. 2006. Eating Up the Amazon. Report. 64 pp.
5 Carey C., Oettli D. 2006. Determining links between agricultural crop expansion and deforestation. A report prepared for the WWF Forest Conversion Initiative. 71 pp.
a WWF. 2006. Facts about soy production and the Basel Criteria. Factsheet. 7 pp.
