An example of human destruction of the earth

1. Global climate change. In the past century, the global average surface temperature rose by 0.3 to 0.6 degrees Celsius, and the sea level rose by 10 to 25 cm. At present, the concentration of carbon dioxide in the earth's atmosphere has increased from 280 ppm( 1750) before the industrial revolution to nearly 360ppm.

2. Destruction and depletion of the ozone layer. Since the ozone hole appeared over Antarctica in 1985, the depletion of the ozone layer over the earth has been increasing. By 1994, the ozone layer over Antarctica had destroyed 24 million square kilometers. Now, the ozone layer over the United States, Canada, Western Europe, the former Soviet Union, China and Japan is thinning.

Because ODS is quite stable and can exist for 50- 100 years, most of the emitted ODS is still in the atmosphere. When they rise to the stratosphere, they will react with the ozone layer there and decompose ozone molecules. Therefore, even if the global emissions of ODS are completely stopped, it will be another 20 years before mankind can see the signs of ozone layer recovery.

3. Acid rain pollution. Now the word "acid rain" has been used to refer to the transfer of acidic substances from the atmosphere to the ground in the form of wet deposition (rain, snow) or dry deposition (acidic particles). Acid rain is mostly sulfuric acid and nitric acid, which mainly comes from the extensive use of fossil fuels by human beings, and a large amount of sulfur dioxide and nitrogen oxides are discharged into the atmosphere. Europe is a major acid rain area in the world, as are the United States and eastern Canada.

In northern Europe, due to the high natural acidity of soil, soil acidification is particularly serious, and acidification of some lakes leads to the extinction of fish. According to the national surface water survey data, acid rain causes 75% of lakes and about half of rivers to be acidified. The Canadian government estimates that 43% of Canada's land (mainly in the east) is highly sensitive to acid rain, and 65,438+04,000 lakes are acidic. Acidification of water body will change aquatic ecology, while acidification of soil will impoverish soil and lead to degradation of terrestrial ecosystem.

4. Land desertification is the most serious environmental and socio-economic problem in the world today. 199 1 year, UNEP assessed the global desertification situation as follows: the global desertification area has reached nearly 3.6 billion hectares, accounting for about 1/4 of the global land area, affecting 1/6 of the global population (about 900 million people) and 100 countries and regions. Moreover, the speed of desertification expansion is that 6 million hectares of land in the world become desert every year, of which 3.2 million hectares are pasture, 2.5 million hectares are dry land, 6.5438+0.25 million hectares are irrigated land, and another 2.65438+0 million hectares cannot grow food because of degradation.

5. Water crisis, many parts of the world are facing serious water crisis. According to international experience, per capita annual 1 1,000 cubic meters of reusable freshwater resources is a basic index, and countries below this index may suffer from long-term water shortage, which will hinder development and harm health. But at present, about 20 countries in the world have fallen below this index, mainly in West Asia and Africa, with a total population exceeding 1 100 million. On the other hand, domestic wastewater, industrial wastewater, agricultural wastewater, solid waste leakage, air pollutants and other water pollution. Has greatly reduced the available fresh water resources in the world.

6. Destruction of forest vegetation. Due to the difficulty of speculation, there is no accurate forest area value in the world. However, it is estimated that the forest area on the earth is about 3-6 billion hectares, accounting for 20%-40% of the land area, of which about half are tropical forests (including tropical rainforests and tropical monsoon forest) and the other half are mainly coniferous forests in the sub-cold zone. According to the measured dry weight of forest plants, tropical forests are twice as large as coniferous forests in frigid zones, so tropical forests account for a large part of the total biomass on land.

7. Biodiversity has declined sharply. Scientists estimate that there are about140,000 species on the earth, but the rate of biodiversity loss on the earth is faster than at any time in history. For example, the extinction rate of birds and mammals may be 100 times to 1000 times higher than that of undisturbed nature.

8. Destruction and pollution of marine resources. It is estimated that 950 million people all over the world regard fish as the main source of protein. However, in recent decades, the over-utilization of marine living resources and the increasingly serious pollution of the ocean by human beings may cause obvious degradation of marine productivity and marine environmental quality on a global scale. 1993, 77.7% of the 1.065438+ billion tons of fish caught in the world came from the ocean. At that time, FAO estimated that more than two-thirds of marine fish were overfished, especially 25% of the fish with data were extinct or endangered due to overfishing, and another 44% of the fish had reached the biological limit.

On the other hand, most of the wastes and pollutants produced by human activities eventually enter the ocean. Every year, billions of tons of sludge, sewage, industrial waste and chemical waste are directly discharged into the ocean, and nearly billions of tons of sludge, wastewater and waste are brought into coastal waters by rivers every year, causing changes in coastal habitats and destroying animal habitats and breeding grounds.