What is alien invasion?

Some "biological immigrants" crossing mountains and seas may be a kind of bacteria, a kind of plant or an animal. When they came to a foreign country, they gained a broad living space because they lost the balance of their natural enemies, grew rapidly and occupied lakes and land, while the "indigenous creatures" withered or even became extinct. This is a biological invasion. "They're coming, they're grabbing the owner's attention."

Biological invasion may be strange to people, but when it comes to foot-and-mouth disease, mad cow disease and even AIDS, people are not unfamiliar. In fact, these are all kinds of biological invasions. Some animals and plants often mentioned in the past are also invasive creatures in some places, such as morning glory, water hyacinth, Mediterranean liriomyza sativae, lantana and whitebait.

Biological invasion can be divided into intentional and unintentional. With the introduction of species, on the one hand, these immigrants may benefit mankind, on the other hand, they may have a certain impact on the local ecological environment and even economic development.

There are no rabbits in Australia. 140 years ago 1859, an Englishman Thomas Austin introduced 24 rabbits and released 13 rabbits for hunting. In this country without natural enemies, they have produced more than 600 million offspring so far. These rabbits often eat tens of thousands of square kilometers of plants, causing other kinds of wild animals to face hunger crisis, and many wild plants may become extinct.

On May 7th, 20001year, IUCN warned in a report that the invasion of domestic brown ants, brown tree snakes and other species to other ecosystems caused huge environmental and economic losses. Invasive species may threaten the survival of local animals and plants, resulting in crop reduction and degradation of seawater and freshwater ecosystems. The report lists 100 of the most invasive alien organisms, including aquatic and terrestrial organisms, invertebrates, amphibians, fish, birds, reptiles and mammals. These invaders include domestic cats, North American gray squirrels, Nile perch, hyacinthus orientalis and brown ants. The most harmful alien species in the world include grey mouse, myna, Asian tiger mosquito, yellow Himalayan raspberry and upright fairy fruit. They are called intruders because their activities are extremely active. On Christmas Island in the Indian Ocean, domestic brown ants killed 3 million crabs in 18 months. Nile perch was introduced to Lake Victoria in East Africa in 1954 to reduce the number of local fish. However, Nile perch preys on fish and competes with local fish for food, resulting in the extinction of more than 200 local fish.

Apart from mad cow disease and foot-and-mouth disease, the disasters brought to human beings are very painful, because harmful organisms are endangering human health and the safety of agricultural organisms all the time. In the second half of the fifth century, the plague invaded the Middle East from Africa and then reached Europe, killing about 654.38 billion people. 1933 China classical swine fever epidemic, resulting in the death of 9.2 million pigs; 197 avian influenza occurred in Hong Kong, and 6,543,800+4,000 chickens had to be destroyed. Only the losses of chicken farmers and chicken vendors were compensated, totaling HK$ 654.38+0.4 billion.

As the World Conservation Union pointed out in the book "Preventing biodiversity loss caused by biological invasion" adopted in Switzerland in February 2000, "For thousands of years, oceans, mountains, rivers and deserts have provided isolated natural barriers for the evolution of rare species and ecosystems. In recent centuries, due to global changes, these barriers have become ineffective, and alien invasive species have crossed the ocean to reach new habitats and habitats and become alien invasive species. "

The strengthening of free trade, economic globalization and the substantial growth of trade and tourism provide more opportunities for the accidental or intentional spread of species than before. Airplanes, ocean-going ships, and a traveler trekking between continents may "land" in a strange environment with species. "Every ship, every plane and every truck is a potential carrier," said an expert.

Just like the legendary snakehead, the vast majority of exotic aquatic invasive species will only show a potential threat to the ecosystem if they live comfortably. Usually it's too late to send them home. However, the new computer model for the Great Lakes can predict what kind of fish may invade and whether this invasion will cause widespread harm to the region.

Most policies and scientific research on invasive species focus on commercialized plants and animals. In the past, few people tried to predict which species might cause problems, only considering whether they had certain characteristics (such as faster growth). Most research work has not attempted to quantify the risk of potential invasive species according to various life history characteristics and invasion routes.

CynthiaKolar, a fishery biologist with the U.S. Geological Survey in Lacrose, Wisconsin, and DavidLodge of Notre Dame University in Indiana put forward some models to assess the risk of introducing many kinds of fish into the Great Lakes region in the journal Science published on165438+1October 8. Their models include life history features collected from literature, such as reproductive success rate and past invasions by other members of the genus. Different from previous work, Kolar and Lodge's method decomposes the invasion process into various stages: introduction, settlement and diffusion. This is very important because, for example, a feature, such as rapid growth, may help species settle down, but it will not help them spread. When Kolar and Lodge applied their model to the previous species invasion, they found that the accuracy of predicting the success of the invasion reached 94%.

However, it is easy to predict the past. Kolar and Lodge then investigated 66 species that might invade the Great Lakes. They confirmed that 16 species will spread rapidly if introduced. The author reports that among the 16 species, 5 may have become annoying settled species.