A World Imperiled: Forces Behind Forest Loss
As the first seven parts of the rainforest section of the site have described, tropical rainforests are incredibly rich ecosystems that play a fundamental role in the basic functioning of the planet. Rainforests are home to probably 50 percent of the world's terrestrial species, making them an extensive library of biological and genetic resources. In addition, rainforests help maintain the climate by regulating atmospheric gases and stabilizing rainfall, protect against desertification, and provide numerous other ecological functions.
However, these precious systems are among the most threatened on the planet. Although the precise area is debated, each day at least 80,000 acres (32,300 ha) of forest disappear from Earth. At least another 80,000 acres (32,300 ha) of forest are degraded. Along with them, the planet loses untold numbers of species to extinction, the vast majority of which have never been documented by science. As these forests fall, more carbon is added to the atmosphere, climatic conditions are further altered, and more topsoil is lost to erosion.
Despite increased awareness of the importance of these forests, deforestation rates have not slowed. Analysis of figures from the Food and Agriculture Organization of the United Nations (FAO) shows that tropical deforestation rates increased 8.5 percent from 2000-2005 when compared with the 1990s, while loss of primary forests may have expanded by 25 percent over the same period. Nigeria and Vietnam's rate of primary forest loss has doubled since the 1990s, while Peru's rate has tripled.
Overall, FAO estimates that 10.4 million hectares of tropical forest were permanently destroyed each year in the period from 2000 to 2005, an increase since the 1990-2000 period, when around 10.16 million hectares of forest were lost. Among primary forests, annual deforestation rose to 6.26 million hectares from 5.41 million hectares in the same period. On a broader scale, FAO data shows that primary forests are being replaced by less biodiverse plantations and secondary forests. Due to a significant increase in plantation forests, forest cover has generally been expanding in North America, Europe, and China while diminishing in the tropics. Industrial logging, conversion for agriculture (commercial and subsistence), and forest fires—often purposely set by people—are responsible for the bulk of global deforestation today.
But enough about the extent and some of the effects of deforestation. What is responsible for this loss? This is the question this section addresses.
Current estimates of tropical forest loss (hectares)
Data source: Hansen et al 2015
Deforestation figures and charts
Deforestation and Degradation
Before expanding further on forest loss it is critical to first explain what is considered "forest" and what is meant by deforestation and forest degradation.
The Food and Agriculture Organization of the United Nations (FAO), the leading source for information on the status of the world's forests, defines forests as land with a tree canopy cover of more than 10 percent and an area of more than half a hectare. FAO says that "forest" includes natural forests and forest plantations but specifically excludes stands of trees established primarily for agricultural production (i.e. fruit tree and oil palm plantations) and trees planted in agroforestry systems.
Other organizations use different standards for defining forests. For example, the United Nations Environment Programme (UNEP) uses 40 percent cover as the threshold for "closed forests" and 10-40 percent cover for "open forests," while the Tropical Ecosystem Environment Observations by Satellite (TREES) project classifies areas with more than 70 percent canopy cover as "dense forests" and those with 40-70 percent cover as "fragmented forest."
Data according to the FAO. Note the differences from the chart above. FAO's data is based on self reporting from forestry departments, while Harris and colleagues used satellite imagery.
To reduce confusion, this site will generally follow FAO's convention, even though it has been criticized for its generous definition of what it considers forest.
FAO defines deforestation as "the conversion of forest to another land use or the long-term reduction of the tree canopy cover below the minimum 10 percent threshold." Depletion of forest to tree crown cover greater than 10 percent (say from 90 percent to 12 percent) is considered forest degradation. Logging most often falls under the category of forest degradation and thus is not included in FAO deforestation statistics. For this reason, forest degradation rates are considerably higher than deforestation rates.
Digging a little deeper, FAO says that "deforestation includes areas of forest converted to agriculture, pasture, water reservoirs and urban areas," but the term "specifically excludes areas where the trees have been removed as a result of harvesting or logging and where the forest is expected to regenerate naturally or with the aid of silvicultural measures."
Deforestation vs. Degradation
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Clear-cutting in Borneo. (Photo by R. Butler)
Continued / Next: Natural forces behind deforestation
- What is the difference between deforestation and forest degradation?
- What are some examples of activities that cause deforestation?
- What are some causes of forest degradation?