The view of biological invaders

Legend has it that ecosystems are formed through long-term evolution. After hundreds of years of competition, exclusion, adaptation and mutual benefit, the species in the system have formed 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.

catalogue

Definition standard

Cause problems

take its toll

Introduction project

What can we do?

invasive species

words explanation

Characteristic invasion mechanism and diffusion mechanism in alien species invasion

1, characteristics of biological invaders

2. Characteristics of invasive ecosystems

3. Areas vulnerable to invasion by alien species

The artificial relationship between human activities and biological invaders

1, intentionally introduced

2. Unintentional introduction

Impact hazard (1) on ecology

(B) the impact on society and culture

(C) the impact on the economy

Original article with the same name

Related data definition standard

Cause problems

take its toll

Introduction project

What can we do?

invasive species

words explanation

Characteristic invasion mechanism and diffusion mechanism in alien species invasion

1, characteristics of biological invaders

2. Characteristics of invasive ecosystems

3. Areas vulnerable to invasion by alien species

Artificial relationship

Human activities and biological intruders 1, intentionally introducing 2, but unintentionally introducing impact hazards.

(1) Impact on ecology (2) Impact on society and culture (3) Impact on economy.

The definition standard of this paragraph is to edit the relevant materials of the original text

Biological invaders: alien invasive species define invasive species as 1) introduced into non-native areas through intentional or unintentional human activities; 2) forming self-regeneration ability in local natural or artificial ecosystem; 3) Causing obvious damage or influence to the local ecosystem or geographical structure.

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What problems will invasive species cause? Directly reduce the number of species, indirectly reduce the number of species that depend on local species, change the ability of local ecosystems and landscapes to control and resist fires and pests, reduce the ability of soil conservation and nutrition improvement, reduce the ability of water conservation and water quality improvement, and reduce the ability of biodiversity protection.

Loss caused by editing this paragraph

What losses have the invasive species caused us? 1. Biodiversity and loss of its functions, including: 2. Benefits of the ecosystem. Biological resources. Social Benefits 5.40% of the world economy and about 80% of the needs of the poor people come from biodiversity. 6. Loss of uniqueness of local species and ecological landscape. Ecotourism income. Local native biological products. Social welfare 10. The more globalization is common, the higher the local value 1 1. The income of surrounding agriculture and forestry decreased 12. Pest control cost 13. The cost of weed control is 14. Decline of soil fertility 15. The ability to regulate and control water resources has declined. Sustainable agriculture and forestry depend on the surrounding or good ecosystem as a barrier against pests and fires.

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The most dangerous large-scale project of introducing alien species intentionally or unintentionally is being carried out in China. In the process of returning farmland to forests on a large scale, a large number of exotic species including eucalyptus, exotic pine and exotic larch are planted, and economic trees are planted at inappropriate altitudes and regions. Large-scale soil erosion control and pasture cultivation mainly rely on the introduction of grass seeds from abroad (especially the United States), while the cultivation, research and utilization of local grass seeds in China are few. Protected area greening uses alien species to restore vegetation, and urban greening uses a large number of alien invasive species for ornamental plants. A great deal of evidence shows that freshwater and mariculture have seriously damaged the biodiversity and ecosystem of water areas, such as golden dragon with five claws and passion fruit.

What can we do to edit this paragraph?

The intentional introduction and spread of alien species should be controlled from the following aspects: what species? Where was it introduced? How much is introduced? What is the application field? It is forbidden to introduce exotic species very close to the reserve, and it is forbidden to introduce them intentionally, unless it is proved that it will not cause harm to the ecosystem and the environment, and the local species do not have the same function. It is forbidden to use alien species in all vegetation restoration projects. Alternanthera philoxeroides and Eichhornia crassipes. Promote the sustainable utilization of local species, strengthen the research on provenance cultivation of local species, mobilize the public to collect and cultivate local species seeds, establish an early warning system for invasive species, establish an information system for exotic species in China, establish a global information system based on information and experience, establish and update a list of the most dangerous invasive species, and establish a convention to limit the spread of these species.

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Alien invasive species refer to those species, subspecies or sub-taxonomic units that have appeared in the past or now beyond their natural distribution and diffusion potential (that is, they cannot exist without direct or indirect introduction or human care), including all parts, gametes or propagules that may survive and reproduce. Alien invasive species is an ecosystem, which did not exist in it originally, but came in through human activities over insurmountable spatial obstacles. Under the natural conditions of human beings, the barrier of mountains and rivers and the differences of natural geographical factors such as climate, soil, temperature and humidity constitute obstacles to species migration, and it is quite difficult to enter a new ecosystem by relying on the natural diffusion ability of species. Although there are also cases where animals, plants or pathogens enter the new system due to changes in climate and geological structure, more and more species migrate intentionally or unintentionally due to human activities. The invasion of alien species is closely related to the establishment, stability and evolution mechanism of ecosystem. After the alien species are introduced into the new balanced ecosystem, they may be excluded from the system because they cannot adapt to the new environment, and they must rely on the help of human beings to survive; It is also possible that it just adapts to the local climate and soil conditions, and there is no creature to compete or limit it in the new harsh environment. At this time, this alien species will become real invaders, break the ecological balance, change or destroy the local ecological environment, and become an alien invasive species. Alien species become alien invasive species when they establish populations in natural or semi-natural ecosystems or habitats and change or threaten local biodiversity.

The characteristic mechanism of editing this paragraph

Invasion and diffusion mechanism in alien species invasion

When an alien species enters a new ecosystem, whether it finally invades depends on two factors: the characteristics of the alien species entering the new environment and whether the environment is easy to be invaded by this species.

1, characteristics of biological invaders

If the environmental conditions such as temperature, humidity, altitude, soil and nutrition are suitable, alien species will breed in the new ecosystem. Although many alien species can form natural populations, most of them remain at a low level and will not cause harm. Alien invasive species that cause biological disasters often have the following characteristics: (1) Strong ecological adaptability; (2) Strong reproductive ability; (3) Strong communication skills.

2. Characteristics of invasive ecosystems

Almost all ecosystems are more or less invaded by alien species, but some of them are more vulnerable to invasion. Like alien invasive species, these fragile ecosystems have some common characteristics. (1) has enough available resources; (2) Lack of natural control mechanism; (3) The frequency of artificial entry is high.

3. Areas vulnerable to invasion by alien species

According to the introduction route of alien invasive species and the characteristics of invasive species and ecosystem, we can predict the areas where alien species are easy to invade in China. (1) Near important ports and docks, on both sides of railways and highways. Exotic species introduced by international freight often land near ports and ports first, and then start to spread and establish small populations after encountering suitable environmental conditions; Ballast water discharged by ships and marine species attached to camps often settle in ports; Exotic species carried by trains and cars can easily settle and spread on both sides of railways and highways. (two) forests and grasslands that are considered to be seriously disturbed. Human activities can directly bring exotic species. Forests, grasslands and other ecosystems were originally stable, but it is seriously believed that deforestation and overgrazing will degrade the ecosystem, reduce its diversity and create favorable conditions for the invasion of alien species. (3) Islands, waters and pastures with low species diversity and simple habitats. Species diversity is low, natural inhibition is low, natural enemies are few, exotic species are easy to survive, and the population is easy to expand. (four) due to fire, flood, drought and other sudden natural disasters and damage to the ecological environment. In these ecological environments, the ecosystem is severely damaged in a short time, the species composition and community structure become simple, and invasive species can easily occupy a large number of niches and become dominant species. (5) Warm and humid areas with good climatic conditions. For example, due to its geographical and climatic conditions, southern China often provides good conditions for the outbreak of alien invasive species.

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Human activities and biological invaders

The most fundamental reason for biological invasion is that human activities have brought these species to places where they should not appear. So we call these species "harmful", which is actually unfair to these species. They just stay in the wrong place, and the cause of this mistake is often some irresponsible activities of human beings. The key to the problem of alien invasive species is man-made.

1, intentionally introduced

It refers to the intentional introduction of a species by human beings, which purposefully focuses a species outside its natural distribution range and diffusion potential (this introduction can be authorized or unauthorized). Such as water hyacinth. It was originally introduced to purify water sources. However, due to the suitable environment and rapid reproduction, it has caused harm to many water sources in China.

2. Unintentional introduction

Refers to the use of people or people's communication system as a medium to introduce a species unintentionally and spread it to places outside its natural distribution. Such as: red fire ants. At the beginning of the 20th century, due to negligence in inspection and epidemic prevention, it invaded the southern United States. This insignificant alien fire ant has caused very important agricultural and environmental health problems and economic losses in the United States.

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Harm of 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 Competition and occupying the niche of local species 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 animals and plants have become major pests that directly endanger the development of agriculture and forestry economy, and can bring direct economic harm to farmland, horticulture, lawn, forest, animal husbandry and aquatic products. 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, an ideal tourist route on Daguan River was built in the 1970s and 1980s, and tourists can start to visit Dianchi Lake and Xishan by boat from 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.

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original text

Author: Mei Tao You won't be surprised when you find one or two beetles you've never seen before on the roadside grass or in your yard. But in the eyes of biologists and ecologists, this may not be trivial. Experts call this kind of "immigrants" who originally lived in a foreign country and moved to a new ecological environment by unnatural means "biological invaders". They will not only destroy the original ecosystem in a certain area, but also cause immeasurable economic losses to human society. In the early days of human civilization, land and navigation technologies were underdeveloped, and the ecological balance of nature was not greatly damaged. Under natural conditions, a dandelion seed may drift with the wind for dozens of kilometers before landing. If the conditions are suitable, it will take root, sprout and grow there. Fish and shrimp in mountain streams may swim with the water and settle down in rivers ... These are all carried out slowly without human intervention, and the time and space span are very limited, so it will not cause serious imbalance of the ecosystem. If a species is not restricted by similar food competition, natural enemy harm and many other factors in the new living environment, it is likely to multiply uncontrollably. 1988, several mussels (mollusks similar to mussels) originally living in the European continent were brought to the North American continent by a cargo ship. At that time, these "stowaways" mixed in the goods at the bottom of the warehouse did not attract the attention of the local people, and they were randomly abandoned in the waters near the Great Lakes. Unexpectedly, however, it has become a "paradise" for bamboo. Without the restriction of natural enemies, the number of scallops has increased dramatically, and almost all the drainage pipes in the Great Lakes have been "occupied" by them. So far, people have spent billions of dollars to clean and replace pipelines. Long-horned beetles from Asia and red ants from South America are two other "invaders" that plague Americans. The former madly destroys trees in Chicago and new york, while the latter specializes in biting people and animals and spreading diseases. "Biological invaders" not only cause immeasurable economic losses to human beings, but also pose a great threat to other species and species diversity in the invaded areas. During World War II, palm tree snakes settled in Guam with a military cargo ship. This reptile living in trees specializes in preying on birds, attacking nests and devouring eggs. Since World War II, 9 species of native birds in Guam 1 1 have been wiped out by brown snakes, and the number of the remaining 2 species is decreasing day by day, which is in danger of extinction at any time. Some biologists have seen palm snakes six times on the plane from Guam to Hawaii. They warned that there are no natural enemies on the island of Hawaii that can inhibit the reproduction of palm snakes. Once the palm tree snake settled in Hawaii, the birds on the island would be extinct. Many biologists and ecologists blame the increasing number of "biological invaders" on the increasingly prosperous international trade. In fact, many "biological intruders" achieve the purpose of "smuggling" by hitchhiking in transnational trade. Take the current global fresh fruit and vegetable trade as an example. There are many insects and insect eggs attached to these goods, including extremely harmful pests, such as Mediterranean fruit flies. Although the animal and plant quarantine centers of customs in various countries strictly guard against these pests, it is difficult to ensure that there are no "bugs" that escape the net because of the huge volume of import and export goods. In addition, transnational pet trade also provides convenience for "biological invaders". In recent years, the news that the introduction of colorful ornamental fish has brought cholera to some areas is often seen in newspapers. Some foreign pets, such as snakes, lizards, bobcats, etc. Often escape from the fence due to the negligence or abandonment of the owner, and gather mountains to harm one side. Some biologists point out that once a certain "biological invader" gains a foothold in the new environment and multiplies on a large scale, its number will be difficult to control. Even in today's highly developed science and technology, people will still be helpless in the face of plants and animals with strong adaptability and reproductive ability. Some scholars in biology and ecology believe that human beings should not interfere too much in the migration process of biological species, because the imbalance is temporary and a species must follow the law of natural selection in the new environment. Not all "biological invaders" can survive, but the strong can survive. Even the strong in the ecosystem are restricted by various factors in the system and cannot do whatever they want. Therefore, the natural balance will eventually be achieved. However, more scholars are against it. They think that the process of natural adjustment is very long. If "biological invaders" are allowed to develop freely, many native species will be doomed to extinction and the species diversity in nature will be seriously damaged. In addition, the economic losses caused by "biological invaders" to human society are also amazing. In the United States alone, the economic losses caused by "biological invaders" are as high as more than 200 billion US dollars every year. How can people be indifferent to such astronomical figures? At present, many countries in the world have begun to realize the seriousness of this problem and taken corresponding measures. For example, the US House of Representatives passed a bill in 1996, requiring relevant agencies to strengthen the monitoring of vehicles that may carry alien species. To this end, the US government is planning an inter-departmental monitoring plan.