Many biologists and ecologists attribute the increase of "biological invaders" to the increasingly prosperous international trade. In fact, many biological invaders.

Biology and ecology have different attitudes towards biological invaders: some people think that the harm of biological invaders can be limited by "natural selection" to achieve a new ecological balance; Others believe that letting "biological invaders" develop freely will cause serious harm to local ecology and human life. Countries all over the world are taking corresponding measures against "biological invaders".

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 went 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 incalculable 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 float thousands of meters with the wind before landing. If all conditions are right, 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 in a new living environment is not restricted by many factors such as competition of similar foods and destruction of natural enemies, it is likely to reproduce 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 attribute the increase of "biological invaders" to the increasingly prosperous international trade. As a matter of fact, many "biological intruders" take "hitchhiking" in cross-border trade to achieve the purpose of "smuggling". 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 because of the owner's negligence or abandonment and escape, hurt one party.

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?