(1) Habitat loss and fragmentation. The global ecosystem has been seriously damaged, resulting in many creatures losing their habitats. The tropical rain forest in 50% species habitat is reduced by half compared with the original area, and the forests in most countries are fragmented and surrounded by degraded land, which damages the ability of forests to maintain the survival of wildlife populations and important ecological processes. China's natural forests have been cut to pieces.
(2) Predatory overuse. The growth of population and the endless demand for biological resources have seriously damaged biological resources. A large number of forests, fish and wildlife resources have been overexploited and hunted indiscriminately, and the survival of species is threatened, and some are on the verge of extinction. For example, the population of antelope, wild deer, precious fur animals and various fish in China has greatly decreased. In 1960s, the economic fish resources in China sea area declined. Due to overfishing, the marine catch has been greatly reduced, such as high-quality fish such as large yellow croaker, which is hardly the fishing season at present. Many wild medicinal plants and precious edible fungi, due to long-term manual picking and excavation, their distribution area and population number have been greatly reduced. Many countries protect animals as people's food, and looking for rare commodities (such as ivory) as pets and rare collections also makes some populations endangered and others extinct.
(3) Environmental pollution. Urban and rural industrial and agricultural sewage discharge, air pollution, heavy metals and refractory chemicals enrichment, resulting in water, air and soil pollution. The discharge of pollutants has overwhelmed the endurance and atmospheric diffusion capacity of ecosystems. Ozone depletion, acid rain and air pollution have all done great harm to today's biodiversity. Pollutants move along the food chain of the ecosystem, resulting in the reduction or disappearance of some sensitive species. In China, the farmland obviously polluted by industrial waste reaches 1 10,000 hectares, accounting for about 10% of the total farmland area, and the area polluted by pesticides also reaches 1 10,000 hectares. Many lakes and rivers in China are polluted by industrial wastewater, which makes some aquatic organisms extinct.
(4) simplification of agricultural and forestry varieties. In order to get a higher harvest in agriculture, a single high-yield variety is often planted, which occupies an important position in the world economy. With the decrease of crop species, the corresponding nitrogen-fixing bacteria, mycorrhiza, predators, pollinators and seed-borne organisms, as well as some coevolutionary species in traditional agricultural systems have disappeared. For example, in Indonesia, 65,438+0,500 local rice varieties have disappeared in the past 65,438+05 years. Agricultural varieties are highly consistent and lack the ability to resist disasters such as pests and diseases. In forestry, for the needs of human beings, woodland with rich species is often destroyed, and a single tree species, such as coffee, oil palm and rubber, is planted, which makes all kinds of creatures lose their original habitats.
(5) Introducing exotic species. The introduction of exotic species will lead to species extinction, because some exotic species often destroy the local traditional food chain and food web, resulting in ecological imbalance. In some areas, due to human settlement, the introduction of exotic species, especially animals, often leads to the extinction of all or part of land and plants. Since 1600, 22 species of amphibians and reptiles have become extinct worldwide due to the introduction of exotic species. In New Zealand, since 1000, due to the introduction of exotic species, 9 species of frogs and lizards have been extinct or nearly extinct, and 23 species and subspecies of local birds are on the verge of extinction. The introduction of fish species into some lakes with extremely high endemic species in the Great Rift Valley in Africa has endangered the local protozoan species. Exotic animals such as midges and snakes may soon lead to the extinction of local native animals; The introduction of herbivores such as sheep and reindeer will also destroy native plants. Exotic species also make native plants extinct. In the Philippines, due to the introduction of pigs, goats and rabbits, 1790 ~ 1840 years, 13 native plants became extinct, including two endemic species. 1992 ~ 1993 bivalve sand shells were found in Dongshan, Fujian, China and Maluan Bay, Xiamen. This species is native to America and was first discovered in Hong Kong waters in1980s. At present, it occupies almost 100% of the surfaces of the above two piles, rafts and all aquaculture facilities, crowding out a large number of barnacles and oysters in the past. Because of the competition for food, it makes agriculture. Another example is Spartina alterniflora and Spartina alterniflora introduced from Britain and the United States in the 1980s, which were planted in coastal beaches of China and received certain ecological benefits. However, due to their rapid reproduction, they compete with aquaculture for space and change the original biological community on the beach. Moreover, the introduction of alien species will also lead to the destruction of the original habitat and cause changes in the ecosystem, so it is necessary to consider the possible consequences of the introduction of alien species and be cautious.
(6) Global climate change. In the next few decades, a huge side effect of air pollution-global warming-will do great harm to life on earth. The increase of greenhouse gases (mainly CO2 and CH4) in the atmosphere caused by human beings may lead to the increase of atmospheric temperature 1 ~ 3℃ in the next century, make the tolerance limit of terrestrial species move to the polar regions 125 km, or increase the vertical height of mountains 150 m ... Many species may not keep up with the expected climate change now, and some species may disappear.