Facts on Forests and Forestry

5. How do forests influence the environment, the climate and humanity?

5.1. Do forests have an effect on climate?
5.2. How do forests affect the process of climate change?
5.3. Do forests provide any other environmental services?
5.4. How important are forests to humanity?

5.1. Do forests have an effect on climate?

The importance of forests on global climate is relatively moderate compared to changes in the polar ice caps, in the temperature of oceans and in the transmission of sunlight and heat from the surface of the earth. Since two thirds of the surface of the globe is covered by oceans and polar ice caps, these have the most significant impact on climate. More...

5.1.1. Forests do have an effect on rainfall. Although on a global scale the main source of water vapor is the surface of the oceans, evaporation from land surfaces, including forests, can be important regionally. In the Mississipi Valley, ‘recycled’ land water was found to account for one third of the average precipitation, whereas in the Amazon forest it accounted for one half. More...

5.1.2. The foliage of the canopy intercepts falling rain and thereby regulates cycles of water flow (into rivers, soils, underground reserves, etc.). Variables such as the foliage density or the soil composition make it difficult to state whether forests increase or decrease water flow. It is clear however that forests help reduce the severity of tropical rainstorms and rapid snowmelt, thus mitigating floods and ensuring a more steady water flow. Forest cover does this by producing litter that protects the soil and allows more water to seep into the ground. If this protection is decreased because of logging or fires, it can lead to increased overland flow, which is quicker to reach and flood rivers. Hydrological processes however are complicated and involve many factors. More...

5.2. How do forests affect the process of climate change?

Forests can be compared to buffers that cushion ongoing climate change. However, when forests are cleared they become significant sources of greenhouse gases. More...

5.2.1. Carbon sequestration is the process by which carbon is stored as plant tissue as a result of photosynthesis. By reducing levels of carbon dioxide from the atmosphere, forests mitigate climate change more than any other ecosystem. Sequestration abilities vary with the type and development stage of a forest. More...

When forests are degraded or cleared, the stored carbon is released back into the atmosphere. Hence the destruction of tropical forests is responsible for some 20% of the total carbon dioxide yearly emissions caused by humans.

5.2.2. Forests store about 40% of all carbon in the terrestrial biosphere. More carbon is stored in forest soils than in forest vegetation. The Northern Hemisphere forests increasingly store carbon while tropical deforestation leads to 1.6 billion tons of carbon released yearly into the atmosphere. Globally forests are currently net sources of carbon. More...

5.2.3. To prevent excessive carbon releases from forests into the atmosphere, the loss of existing forests should be slowed and reforestation should be enhanced. Non-living carbon reservoirs (like agricultural soils) and artificial reservoirs (like timber products) should also be increased. Energy related carbon emissions should also be reduced. More...

5.3. Do forests provide any other environmental services?

Forests are useful in many ways, from the protection of soil to the supplying of water for hydroelectricity. More...

5.3.1. Forest canopies shelter the soil surface while roots anchor soil and rocks. This helps prevent erosion, avalanches, and rockfall in mountainous areas. More...

5.3.2. Mountain forests are also an important source of water for irrigation and power generation. By releasing water slowly, they reduce downstream flooding. Forests produce timber and other products, and fuel for local populations. Mountain forests have exceptional biodiversity due to the inaccessibility between valleys, but many species are unfortunately also endangered. More...

5.4. How important are forests to humanity?

Goods and services provided by forests include timber and wood fibre, food, shelter and energy. More...

5.4.1. Plants from the forest can be used as medicines

Plants and animal parts from forests have medicinal purposes in both ‘conventional’ medicine and ‘indigenous knowledge’. More...

5.4.2. Forests have spiritual values

Some of world’s religions have initiated conservation actions for forests: namely the Buddhist, Shinto, Maronite, Swedish church and Zoroastrians. More...

5.4.3. Environmental economics quantifies the value of forest services

Environmental economics has tried to derive estimated values for some of the non-timber products and services of forests. The absence of such estimates is pinpointed by some as one reason why market-oriented economies tend to promote harvesting for timber rather than conservation or more sustainable uses. Critics claim forests should not be ‘commoditized’. Others argue that many factors cannot be accounted for in economic terms. More...