Other Ecosystem Services

Serious and urgent as the greenhouse gas (GHG) emission reduction task is, it is by no means the full story on the value of tropical rainforests. Rainforests provide a range of other large-scale ecosystem services, as well as many more localized goods and services, such as regulating rainfall, preventing flooding and soil erosion, preserving biodiversity, limiting prevalence of disease and providing livelihoods for local people.

Rainforests and rainfall

Rainforests are huge freshwater regulators. Rain that falls on them is itself a function of the diversity of life in these forests. The combined activity of animal and plant life releases huge quantities of volatile organic compounds, which create the fine condensation nuclei around which water droplets form. Moisture is held in these humid, cool ecosystems and evaporates slowly to make clouds.

It has been estimated that a rainforest tree can transpire eight to ten times more water vapour into the atmosphere than an equivalent area of the ocean evaporates [1]. Collectively the Amazon rainforest releases 20 billion tonnes of moisture into the atmosphere each day. If put into a kettle and boiled, this would require energy equivalent to the largest hydro dam in the world working on full power for 135 years.

Some models suggest that the removal of rainforests could result in reductions in rainfall globally, including in the American Mid-West and parts of Central Asia [2]. At a regional scale the water vapour from the Amazon feeds agriculture in Southern Brazil and may be carried as far south as the agricultural heartland of the La Plata Basin in Argentina. The extent to which food and energy security (for hydro power) in the region is underpinned by these ecosystem services should not be underestimated.

Flooding and soil erosion

Tropical rainforests act like a giant sponge, soaking up rainfall brought by tropical storms, while anchoring soils and releasing water slowly through evaporation. This ensures the regular flow of clean water in a region and moderates destructive flood and drought cycles, which are more common on degraded land [4].

Soil erosion is a well known consequence of deforestation. Studies in the Ivory Coast found that forested slopes lost 0.03 tonnes of soil per year per hectare, whereas bare slopes lost 138 tonnes per hectare [5]. This is because the matrix of forest tree roots holds the soil together, which reduces the risk of land slides, and helps it to absorb water, which enables a slow release into streams and rivers, maintaining the water flow and reducing the frequency of flooding [6].

The effects of soil erosion are far reaching. Rivers carry the eroded soils downstream, and the resulting siltation adversely affects hydroelectric reservoirs and irrigation infrastructure, raises river beds (increasing the severity of floods), and creates shoals and sandbars making river navigation more troublesome. The increased sediment in rivers smothers fish eggs, causing lower hatch rates, and as sediment reaches the ocean, the water becomes cloudy, causing regional declines in coral reefs, and affecting coastal fisheries.

Biodiversity

It is believed that tropical rainforests are home to over half of the world's species of plants and animals; they appear to be the most diverse expressions of life ever to have evolved. The enormous variation of life and its delicate interactions within rainforest ecosystems are only just beginning to be understood - scientists have so far been able to study a mere 1 percent of the species in rainforests.

The economic value of this biodiversity is inestimable. A considerable share of the developed world's diet originated in the tropical rainforest. Foods and crops derived from the rainforest include staples such as potatoes, rice and yams; fruits; nuts; spices; and of course, coffee and chocolate. Agricultural scientists are now cross-breeding wild strains of rainforest crops with domestic strains in order to improve yields, resistance to parasites and other physical characteristics [7].

As is well-known, rainforests have been the source of compounds vital to the discovery and potency of many modern medicines. The US National Cancer Institute believes that more than 1,430 varieties of tropical plants have properties that could potentially treat cancers, and that more than 70% of plants identified as having anti-cancer properties are found in the rainforest [8].

However, tropical deforestation is causing the mass extinction of species: it is estimated that 50,000 plant, animal and insect species are lost each year, which equates to 137 species every single day [9].Most of the species that exist in rainforests are still inadequately researched. Therefore, their potential value to humanity, and to the maintenance of environmental sustainability, is unknown. Evolution will not make good their extinction within a million years, but the loss of this unique genetic database could be felt within a generation.

Disease

Damaged forests can result in increased disease frequency: for example, the biting incidence of malaria-bearing mosquitoes can rise in degraded forests. The 2005 drought in the Amazon caused catastrophic dysfunction of local transport affecting health services to millions of people. Disruptions to high-quality drinking water supplies, natural medicines and other forest goods resulting from forest clearing can also threaten the health of local residents.

Non-timber forest products

There are a great many products harvested from rainforests which provide food and livelihood necessities to local populations, often at low or zero prices. Some of these products enter more formal markets, and some, such as rattan, guarana, brazil nuts, latex from bush rubber gathering and so forth, have developed large and sometimes international markets.

Source
1 Global Canopy Programme, ‘Forests first in the fight against climate change' (2007)
2 D. Werth & R. Avisar, ‘The local and global effects of African deforestation', Geophysical Research Letters (2005), vol. 32, no. L1270
3 http://rainforests.mongabay.com/0902.htm
4 http://www.mongabay.com
5 http://rainforests.mongabay.com/0903.htm (accessed May 2008)
6 http://www.globalcanopy.org/main.php?m=3&sm=11&ssm=63
7 http://rainforests.mongabay.com/1007.htm (accessed May 2008)
8 Haidet, A. (2003) The Medicinal Value of the Rainforest (http://jrscience.wcp.muohio.edu)
9 http://www.rain-tree.com/facts.htm (accessed May 2008)