Deforestation
Deforestation refers to the purposeful clearing of forested land or decrease in forest areas that are lost for other uses such as agricultural croplands, urbanization, or mining activities. Greatly accelerated by human activities since 1960, deforestation has been negatively affecting natural ecosystems, biodiversity, and the climate. The UN’s Food and Agriculture Organization estimates the annual rate of deforestation to be around 1.3 million km2 per decade.
Deforestation represents one of the largest issues in global land use. Estimates of deforestation traditionally are based on the area of forest cleared for human use, including removal of the trees for wood products and for croplands and grazing lands. In the practice of clear-cutting, all the trees are removed from the land, which completely destroys the forest. In some cases, however, even partial logging and accidental fires thin out the trees enough to change the forest structure dramatically.
Today, the greatest amount of deforestation is occurring in tropical rainforests, aided by extensive road construction into regions that were once almost inaccessible. Building or upgrading roads into forests makes them more accessible for exploitation. Slash-and-burn agriculture is a big contributor to deforestation in the tropics. With this agricultural method, farmers burn large swaths of forest, allowing the ash to fertilize the land for crops. The land is only fertile for a few years, however, after which the farmers move on to repeat the process elsewhere. Tropical forests are also cleared to make way for logging, cattle ranching, and oil palm and rubber tree plantations.
Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated deforestation occurs in tropical rainforests. About 31% of Earth's land surface is covered by forests at present. This is one-third less than the forest cover before the expansion of agriculture, a half of that loss occurring in the last century. Between 15 million to 18 million hectares of forest, an area the size of Bangladesh, are destroyed every year. On average 2,400 trees are cut down each minute.
Deforested lands are being replanted in some areas. Some of this replanting is done to replenish logging areas for future exploitation, and some replanting is done as a form of ecological restoration, with the reforested areas made into protected land. Additionally, significant areas are planted as monotypic plantations for lumber or paper production. These are often plantations of eucalyptus or fast-growing pines—and almost always of species that are not native to the places where they are planted. There are approximately 1.3 million square km (500,000 square miles) of such plantations on Earth.
Many replanting efforts are led and funded by the United Nations and nongovernmental organizations. However, some national governments have also undertaken ambitious replanting projects. For example, starting in 2017, the government of New Zealand sought to plant more than 100 million trees per year within its borders, but perhaps the most ambitious replanting project took place in India on a single day in 2017, when citizens planted some 66 million trees.