Natural environment degradation refers to the destruction and loss of native species and natural processes such that only certain components of the original biodiversity and ecological functions persist, often with significantly altered natural communities. The main impact of these changes is to simplify the Earth and simplification itself leads to the danger of collapse. By the mid-21st century, humans will have transformed almost every part of the planet, apart from uninhabitable stretches such as deserts, mountains, tundra and polar regions.
Humans alter the natural environment in three major ways: (1) transforming the land and the sea, through land clearing, forestry, grazing, urbanization, mining, trawling, dredging, and so on (activities often called "development"); (2) adding or removing species and genetically distinct populations via habitat alteration or loss, hunting, fishing, and introductions and invasions of species; and (c) altering the major biogeochemical cycles, of carbon, nitrogen, water, and synthetic chemicals.
Most degradation of natural resources results from the cumulative activities of farmers, households and industries, all trying to improve their socio-economic well-being. These activities can be counter-productive for several reasons. People may not completely understand the long-term consequences of their activities on the natural resource base. Ill-defined or badly enforced property rights may result in environmental losses, as in the case of communal grazing lands, tree crops or water resources. Poverty can undermine the efficiency of market processes in accounting for long-term environmental concerns.
Economic activity depends heavily on the natural resource base in most developing countries. In effort to claw their way out of debt and poverty, the countries have been forced to exploit their natural resources. Desertification, deforestation, soil and water degradation have reached enormous proportions. These environmental changes have a direct and detrimental effects on their development efforts and may limit their growing populations in attaining substantially higher living standards.
A detailed study by UNEP-WCMC in 2002 showed that unsustainable resource consumption on a global scale has been happening since the 1980s. While in 1961, only 70 per cent of the Earth's regenerative capacity was being used, parity was reached by the mid-1970s; by 1999, 25 per cent more was being used than could be regenerated, meaning that the Earth now needs 15 months to replenish what humans take out of the biosphere every year. The net effect is that natural resources are wearing out because they cannot be replaced by biological processes. That applies to such essentials as arable land, grazing areas, timber, fish, "infrastructure" (water, air etc.) and fossil and nuclear fuels.
Some of the key points reported by the World Resources Institute in 2000 are outlined: (1) Half of the world's wetlands were lost in the previous century; (2) Logging and conversion have shrunk the world's forests by as much as half; (3) Some 9 percent of the world's tree species are at risk of extinction; (4) Tropical deforestation probably exceeds 130,000 square kilometers per year; (5) Fishing fleets are 40 percent larger than the ocean can sustain; (6) Nearly 70 percent of the world's major marine fish stocks are overfished or are being fished at their biological limit; (7) Soil degradation has affected two-thirds of the world's agricultural lands in the last 50 years; (8) Some 30 percent of the world's original forests have been converted to agriculture; (10) Dams, diversions or canals fragment almost 60 percent of the world's largest rivers; (11) Twenty percent of the world's freshwater species are extinct, threatened or endangered and at least 10,000 freshwater fish species are threatened globally. The report states that that while our knowledge of ecosystems has increased dramatically, it has not kept pace with human ability to alter them.
Humans moved into South America more than 10,000 years ago. By 4,000 years ago, farmers had completely stripped the trees from mountain sides and planted tubers, like potatoes, and cereals, like quinoa, from which people made bread. Then, 2,000 years ago, the climate cooled and the crops failed, bringing widespread soil erosion, triggering an exodus from the Andes. In about 1,200 AD the climate improved, people returned and the resulting agrarian societies were unified into the Inca civilization, stretching from present-day Colombia to Bolivia. Around 1500, the climate cooled again and the crops began failing, the food stocks were depleted and the Incas were in trouble even without the Spaniards.
Studies of ancient nests made by rock hyraxes, a species of rodent, have shown that the ancient Jordanian city of Petra starved because people cut down its surrounding oak and pistacchio forests, creating an eroded, shrub-lined desert. Farming became impossible.
[Former socialist countries] In western Poland under communist rule, entire areas were rendered unfit for breathing. Czechoslovakia has created moonscapes where ancient forests stood. The Hungarian authorities have been building a hydroelectric power system that diverts the river Danube so drastically that drinking water for the Budapest area is endangered. Romania's Ceausescu built a canal between the Danube and the Black Sea and the Danube delta was being bulldozed for further construction. In former Soviet Union the Aral Sea has shrunk by two-fifths since 1960, leaving behind a salty, man-made desert.