Through processes of respiration and through the decay of organic matter or burning of biomass, forests release carbon. A carbon ‘sink’ is formed in the forest when the uptake of carbon is higher than the release. The conversion of forested to nonforested areas in developing countries has had a significant impact on the accumulation of greenhouse gases in the tmosphere, as has forest degradation caused by over-exploitation of forests for timber ...

Demand for land for production of biomass for energy is putting increasing pressure on forests. Energy security concerns, high oil prices and climate mitigation policies aimed at replacing fossil fuels with renewable energy, have all led to a greater interest in biofuels. The transport sector is using increasing quantities of ethanol, mainly produced from sugar cane, corn and cassava, as a substitute for petrol (gasoline), and biodiese...

Decreases and increases in forest area, 1940-2005. Costa rica has recently recorded a change from having a net loss of forests to having a net gain in forest area.

In Central Africa, species under threat from poaching include elephants and rhinos. Rhinoceros horn is used in traditional Asian medicine, believed to reduce fevers and even prevent loss of life. Other parts of the rhino, including the skin and bones, are also used for their supposed medicinal qualities. Demand for rhino horn has increased substantially in recent years.

In 2005, 2.8 per cent of total global forest cover was made up of productive forest plantations, amounting to an area of approximately 110 million hectares (FAO 2006a). According to the FAO, there was an increase of approximately 40 per cent in the area of the world’s forests plantations with productive functions in the 15 years from 1990. Studies indicate that this growth – a marked trend in recent years – is set to continue (e.g., MA...

Changes in area covered by forest, 1990-2005.

Forests can regulate groundwater levels and increase drainage of soils where the water table is close to the surface. If there are salts in the upper soil layers, then removal of forests can result in raised groundwater levels and the movement of salts into the rooting zone of plants (FAO 2008c).

The Amazon is now part of a national and international economy which, through globalization, is responding to market demands, accelerating the rate at which agricultural crops and cattle ranching are replacing or impoverishing native forests.

The micro-climate associated with forest areas is often a critical factor in growing cash crops. In East Africa, tea is grown in areas adjacent to montane forests where conditions for tea production are optimal due to constant moisture levels, air temperatures between 10° and 30° C and soil temperatures between 16° and 25° C. The high moisture levels in these montane forests combined with the high heat capacity of water reduces the day...

Around the world, conflicts and wars are, directly and indirectly, taking a toll on forests and the communities that rely on them for their livelihood. Dense forests in remote areas provide safe haven for refugees fleeing from conflict, which can result in overexploitation of forest resources.

Indonesia and Malaysia are major producers of palm oil: in 2006 these two countries accounted for 85 per cent of total world production and 88 per cent of global exports (FAO 2008). Over the past decade, the area covered by oil palms in Indonesia has quadrupled, covering 4.1 million hectares in 2006 (FAO 2008). In Latin America, cattle ranches are expanding rapidly (FAO 2007a) and, according to one study, accounted for an estimated 70 pe...

Mangrove forests occur naturally in intertidal zones along sheltered shorelines and in deltas in tropical regions. They are vital breeding grounds for fish and shrimp and also provide a buffer against coastal hazards such as storms, cyclones, wind and salt spray by reducing wind and wave action (Braatz et al. 2007).

In Latin America, cattle ranches are expanding rapidly (FAO 2007a) and, according to one study, accounted for an estimated 70 per cent of deforestation in Brazil in 2007 (Malhi et al. 2008). In the Brazilian Amazon region, ranches cover an area of at least 8.4 million hectares in total.

Growing global demand for land for the production of agricultural commodities has resulted in sometimes irreversible changes to the world’s forest cover. The Amazon is now part of a national and international economy which, through globalization, is responding to market demands, accelerating the rate at which agricultural crops and cattle ranching are replacing or impoverishing native forests (Nepstad et al. 2006).

Around the world, conflicts and wars are taking a toll on forests and on the communities that rely on them for their livelihood. Dense forests can serve as hideouts for insurgent groups or can be as a vital source of revenue for warring parties to sustain conflict.

Forest cover varies depending on how it is defined. The crown cover threshold and the land use criterion are, in most cases, the most critical factors defining forests.

Over the past 40 years, about a fifth of Brazil’s Amazon rainforest has been deforested (Reuters 2008). Official statistics show that annual deforestation has been close to 20 000 square kilometres over the last 10 years, reaching a peak of 27 429 square kilometers in 2004, and then being reduced annually to 11 224 square kilometers in 2007 (INPE 2008).

The present environmental situation – heavily influenced by climate change – could lead to a massive destruction of forests and the extinction of countless species. For example, modelling focusing on the Amazon region has indicated that 43 per cent of 193 representative plant species could become nonviable by the year 2095 due to the fact that changes in climate will have fundamentally altered the composition of species habitats (Miles...

Forests can undergo changes in various ways. Forest areas can be reduced either by deforestation or by natural disasters, which can result in the forest being unable to naturally regenerate. Conversely, forest areas can be increased – through afforestation or by the natural expansion of forests.

Defining what constitutes a forest is not easy. Forest types differ widely, determined by factors including latitude, temperature, rainfall patterns, soil composition and human activity.