1) is introduced into non-native areas through intentional or unintentional human activities;

2) Self-regeneration ability has been formed in the local natural or artificial ecosystem;

3) Causing obvious damage or influence to the local ecosystem or geographical structure;

Why do alien species cause invasion?

The ecosystem is formed through long-term evolution, and the species in the system have been competing, repelling, adapting and helping each other for hundreds and thousands of years before they form a close relationship of interdependence and mutual restriction. After the introduction of alien species, they may be excluded from the system because they cannot adapt to the new environment, and they must be helped to survive; It is also possible that this introduced species may become real invaders, upset the balance, change or destroy the local ecological environment, because there are no competing or restricted creatures in the new environment.

Harm of alien biological invasion

(A) the impact on the ecology

Why do exotic creatures not cause harm in the country of origin, but may have adverse effects after entering new areas? Due to the limitation of habitat, natural enemies, competition among species and human interference, a certain organism has actually formed a harmonious ecosystem with the external environment, so the species is very "moderate" in the ecosystem; When people consciously introduce (or unintentionally bring) this species into the new environment of ecosystem B, only this species is introduced or brought in, but it is not (nor possible) introduced at the same time in the habitats of origin, natural enemies, competition and interference. Therefore, this species may "do whatever it wants" in the more suitable environment of ecosystem B, develop explosively, and be anti-customer-oriented, which will have a negative impact on ecosystem B, that is, in the more suitable environment of ecosystem B. When a species is introduced into a new habitat, if it becomes wild out of human control, it is easy to spread wildly under suitable climate, soil, water and transmission conditions, forming a large-scale single-superior community, destroying local animals and plants, endangering the survival of local endangered animals and plants, and causing the loss of biodiversity.

The mechanism and ecological impact of alien invasive species on the ecosystem are as follows:

1. The competition and occupation of local species niches make local species lose their living space.

2. Competing for food with local species or directly killing local species will affect the survival of local species.

3. Secrete and release chemicals to inhibit the growth of other species. Some exotic organisms such as ragweed can release allelochemicals such as phenolic acids, polyacetylenes, sesquiterpene lipids and sterols, which have obvious inhibitory and repulsive effects on millet such as Gramineae and Compositae. Mikania micrantha can also secrete allelochemicals to affect the growth of other plants.

4. By forming a large-scale single-superior community, species diversity is reduced, and other species that rely on local species diversity have no suitable habitat. The coverage rate of water hyacinth in rivers, lakes and ponds can often reach 100%, which leads to the death of aquatic animals due to the decrease of dissolved oxygen in water. The dominance of ragweed was 0.85 ~ 1.0 and the community diversity was 0 ~ 0.62. Due to Mikania micrantha crowding out local plants, macaques on Neilingding Island in Guangdong lack suitable food and can only be artificially fed at present. The spread of Eupatorium odoratum in Xishuangbanna Nature Reserve has endangered local plants such as Polygonum perfoliatum and herbivorous insects that depend on Polygonum perfoliatum for survival. Ranunculus ternatus in Gulangyu, Xiamen, climbs green trees, forming a large single-superior community on the crown, affecting the photosynthesis of trees and causing death.

5. Excessive utilization of local soil moisture is not conducive to soil and water conservation. Eucalyptus grandis was introduced from Australia and planted in many forest farms in Hainan Island and Leizhou Peninsula. Some places absorb a lot of water, which is very unfavorable to soil and water conservation and causes soil dryness. Continuous planting on a piece of land will make the soil fertility lower and lower, and even form a barren land. Therefore, the introduction of Eucalyptus grandis should be tailored to local conditions and controlled purposefully according to needs.

6. Destroy the naturalness and integrity of the landscape. Four species of American cactus introduced in the late Ming Dynasty formed dominant communities in the coastal areas of South China and southwest dry-hot valleys. The original natural vegetation landscape there is hard to see. Some invasive species, especially lianas, such as Ranunculus ternatus in Xiamen, can completely destroy the well-developed and rich forest landscape.

7. Affect genetic diversity. With the fragmentation of habitat, the remaining secondary vegetation is often divided, surrounded and infiltrated by invasive species, which further fragmentates the protozoan population and causes inbreeding and genetic drift of some vegetation. It is worth noting that, unlike the destruction of the environment by human beings, the destruction of the environment and the threat to the ecosystem by alien invasive species are long-term and lasting. When human beings stop polluting an environment, the environment will start soon and gradually recover; However, when an alien species stops being introduced into an ecosystem, the individuals of the introduced species will not disappear automatically, but most of them will use them to reproduce and spread in the new environment without the control of their original natural enemies, and it is often very difficult to control or remove them. However, local endemic species that have been extinct due to the exclusion and competition of alien species cannot be recovered. Therefore, the threat of alien species to biodiversity should be paid enough attention.

(B) the impact on society and culture

Alien invasive species reduce species diversity by changing the natural ecosystem, and also do serious harm to local society, culture and even people's health. China is a multi-ethnic country, and all ethnic groups, especially the Dai, Miao and Buyi, have their unique animal and plant resources and distinctive ecosystems around them, which play an important role in the formation of local unique national culture and lifestyle. However, due to the constant competition of exotic invasive plants such as Eupatorium adenophorum and Eupatorium adenophorum, biological invasion is silently weakening the foundation of national culture.

Exotic species will pose a direct threat to human health. Ragweed pollen is one of the main pathogens of human allergy, and the "hay fever" caused by it has brought great harm to human health in many countries around the world. Some exotic animals, such as Ampullaria gigas, are intermediate hosts of human and animal parasitic diseases, and muskrats can spread hare fever, which is easy to bring health problems to surrounding residents. Mad cow disease, foot-and-mouth disease and AIDS are great challenges to human survival.

(C) the impact on the economy

Alien invasive species will bring direct and indirect economic harm. It is conservatively estimated that exotic species bring hundreds of billions of dollars in economic losses to China economy every year.

1. Alien invasive plants and animals have become the main pests that directly endanger the economic development of agriculture and forestry.

Alien invasive animals and plants will bring direct economic harm to farmland, horticulture, lawn, forest, animal husbandry and aquaculture. The yield loss caused by Alternanthera philoxeroides in the whole growth period of rice, wheat, corn, sweet potato and lettuce reached 45%, 36%, 65, 438+09%, 63% and 47% respectively. Guangdong, Yunnan, Jiangsu, Zhejiang, Fujian, Shanghai and other provinces and cities have to salvage water hyacinth manually every year. Only Wenzhou City, Zhejiang Province and Putian City, Fujian Province spent 6.5438+0.00 million yuan and 5 million yuan respectively on artificial fishing of water hyacinth. There is no accurate statistics on the total cost in China, which exceeds at least 654.38+0 billion yuan. The agricultural irrigation and irrigation brought by water hyacinth was first discovered by Liriomyza sativae in Hainan in 1993. By 1998, it has occurred in 2 1 provinces and cities across the country, with an area exceeding1300,000 hectares. It parasitized 22 families 1 10 plants, especially vegetables and melons, and suffered seriously. Bursaphelenchus xylophilus, known as "Bursaphelenchus xylophilus", has spread to six provinces in Jiangsu and Zhejiang in just ten years, covering an area of about 66,000 hectares, posing a great threat to scenic spots such as Huangshan and Zhangjiajie.

In international trade activities, exotic species often cause trade frictions between countries and become an important excuse or means of trade sanctions. In recent years, the problem of Anoplophora glabripennis has caused tens of millions of economic losses to the foreign trade of wooden packaging products exported to the United States.

2. Exotic pests bring losses to tourism by affecting the ecosystem.

For example, in Kunming, Yunnan Province, an ideal tourist route on Daguan River was built in 1970s and 1980s, and tourists can visit Dianchi Lake and Xishan Mountain by boat from downtown Kunming. However, since the early 1990s, the water hyacinths in Daguan River and Dianchi Lake have grown wildly, covering the whole Daguan River and part of Dianchi Lake, forcing this tourist route to be cancelled, and the original supporting tourist facilities on both sides of Daguan River have to be scrapped or used for other purposes.

3. Exotic organisms cause indirect economic losses by changing a series of adverse effects such as water, soil and climate. Compared with direct economic losses, indirect losses are often difficult to calculate. But it doesn't mean that the indirect loss is small. For example, a large number of water hyacinth plants died and mixed with sediment deposited on the bottom of the water, which raised the riverbed and gradually turned many rivers, ponds and lakes into swamps, some of which were abandoned, which adversely affected the surrounding climate and natural landscape and aggravated the harm of drought and flood disasters; Moreover, water hyacinth plants absorb a lot of toxic substances such as heavy metals and sink into the water after death, which causes secondary pollution to the water quality and aggravates the pollution degree. Although these losses are difficult to calculate accurately, they cannot be ignored.

List of the first batch of alien invasive species

1 .Eupatorium adenophorum 2. Mikania micrantha

3. Alternanthera philoxeroides. ragweed

5. poisonous wheat 6. Spartina alterniflora

7. flying grass 8. Eichhornia crassipes

9. False sorghum 10. Sugarcane moth

1 1. Beetle.

13. Hyphantria cunea 14. African snail

15. Pomacea canaliculata 16. bullfrog