Seventh grade biology chapter 7

1. Due to people's deforestation, the forest coverage area is getting smaller and smaller, and the forest has lost its adjustment ability. Therefore, in recent years, there have been droughts or floods, serious soil erosion, land desertification, mudslides in some areas and landslides on both sides of the Yangtze River and the Yellow River. Especially in recent years, sandstorms have appeared in some cities, which have brought great harm to people's lives and work.

At present, some places have been deforestation before and after land extension, which has brought forestry production and ecological benefits.

Have a great influence. According to the statistics of Nanyang Intermediate People's Court in Henan Province, before and after the land extension, it was because of deforestation.

The number of criminal cases formed has greatly increased. Since April last year alone, 37 cases have been accepted and 37 cases have been concluded, including 5 years.

14 cases of fixed-term imprisonment, 23 cases of criminal detention, probation and fines.

The main reasons for deforestation have emerged.

Because of the following points:

First, the land changed hands. The first round of land contract expires due to the death of the original contractor or the death of villagers or land managers.

The ownership relationship has changed, the land has changed hands, and the price of trees has not been agreed, leading to deforestation.

The second is policy mistakes. The first round of land contract expires, and the extension policies formulated by some places are inconsistent with the "big" of the central government.

The policy of "maintaining stability and fine-tuning" is inconsistent, which harms the interests of farmers and leads to deforestation.

The third is interest-driven. Wood processing plants in some areas have raised the purchase price, which makes some farmers only pay attention to the present.

Interests, only talking about economic rights, not talking about the obligation to protect the environment, cutting down trees or forests on the original land.

The Central Committee has repeatedly reminded that in the second round of land contracting, it is necessary to prevent deforestation. There are still some places

Or regardless of the overall situation, leading to deforestation.

There are three basic conditions for the formation of sandstorm weather: first, there must be sand sources; second,

There must be strong cold air, that is, strong wind, and the third is the interaction between cold and warm air. The sand comes from the desert.

Degraded forests and grasslands or dry loose land without vegetation cover and sediments from urban and rural construction sites.

Cyclones and low pressure produce vertical upward movement, blowing up dust and forming sandstorms.

weather

Large-scale reclamation, excessive logging and grazing have caused soil desertification and expanded the sand source of sandstorms.

Main failure modes of sandstorm

(1) Strong wind: Strong wind accompanied by fine dust damages buildings and public facilities, causing death.

⑵ Sand burial: Farmland, channels, cottages, railways, grasslands, etc. are buried by a large number of quicksand in the form of quicksand, especially posing a serious threat to transportation.

⑶ Soil wind erosion: The dust source and affected area of each sandstorm will be harmed by wind erosion in different degrees, and the depth of wind erosion can reach 1 ~ 10 cm. It is estimated that the annual loss of soil fine matter caused by sandstorms in China is as high as 106 ~ 107 tons, most of which are below 10 micron, which seriously damages the land productivity of farmland and grassland in the source area.

⑷ Air pollution: In the source area and influence area of sandstorm, the inhalable particulate matter (TSP) in the atmosphere increases, and air pollution intensifies. Taking 1993 "5.5" sandstorm as an example, the outdoor air TSP concentration in Jinchang, Gansu Province reached 10 16 mg/m3, and the indoor air TSP concentration was 80 mg/m3, exceeding the standard by 40 times. From March to April, 2000, Beijing was affected by sandstorms, and the number of days when the air pollution index reached Grade 4 or above was 10, which also affected many cities in eastern China. From March 24th to 30th, the daily pollution index of Nanjing, Hangzhou and other cities 18 exceeded Grade IV.

3. Common birds are shotguns, mousetraps can also catch birds, dig bird nests, and raise birds in a large number of cages (such as thrushes). ) and smuggling wild birds; Large-scale deforestation and mountain burning lead to the reduction and fragmentation of bird habitat, the lack of food resources, and the interference of human activities on its reproduction, which will lead to the decline of bird population, partial extinction of species, population degradation and other problems; Environmental pollution also seriously threatens the survival of birds. The pollution of water, air and soil will lead to the decrease of bird food resources, decreased immunity, unfavorable mutation and deformity, decreased fecundity and individual death.

As an important link in the biological chain, birds are an important part of various biological communities. They control the number of insects, small mammals, reptiles and other species, provide rich species resources for biodiversity, and have high aesthetic and bioethical values and scientific research value. If the number of birds decreases, it will lead to the imbalance of ecosystem structure, the degradation of communities, the increase of insects and other organisms, and the plants that rely on birds to spread and reproduce will face the danger of local extinction.

Most people have no understanding of the value of birds and their value in the ecosystem, and have not formed a certain sense of protection. Some people kill wild birds for enjoyment, some people kill and sell wild birds for profiteering (this is very serious damage to precious species such as raptors), some people consume bird resources for curiosity, and excessive bird watching behavior will also seriously affect the lives of some birds. Some people, governments and enterprises do not consider the damage to the ecological environment when pursuing economic interests, but only seek immediate interests.

4. The eutrophication of Taihu Lake, rural non-point source pollution is an important reason. In July, 2003, one of the 863 major scientific and technological projects of the Ministry of Science and Technology, "Complete set of technologies for non-point source pollution control in river network areas", was implemented in Dapu Town, Dingshu Town, Yixing City, Wuxi. The total investment of this project is more than 50 million yuan, and the scope of pollution control is 20 square kilometers. Including rural domestic sewage treatment, farmland nitrogen and phosphorus control, water purification and water restoration in river network area, pollution control and ecological restoration in estuary area. It is the first rural non-point source pollution control demonstration site in Taihu Lake Basin. Through three years of unremitting efforts, the project has achieved phased results.