Some people say that a country should not introduce any species, otherwise it will cause disaster. Is this view correct? Please tell me your reasons.

You won’t be surprised when you find a beetle or two you’ve never seen before in your lawn or in your yard. But in the eyes of biologists and ecologists, this may not be an ordinary thing. Experts call these "immigrants" who originally lived in foreign countries and entered new ecological environments through unnatural means "biological invaders" - they will not only destroy the original ecosystem of a certain area, but may also It has caused immeasurable economic losses to human society.

In the early days of human civilization, land and navigation technology were not yet developed, and the ecological balance in nature was not greatly damaged. Under natural conditions, a dandelion seed may float in the wind for several kilometers before falling to the ground. If the conditions are suitable, it will take root, sprout, and grow there; fish and shrimp in mountain streams may swim with the current. Settling down in the big rivers... All of this is done slowly without human intervention, and the time and space spans are very limited, so it will not cause serious imbalances in the ecosystem.

If a species is not restricted by many factors such as competition for food from the same species and damage from natural enemies in a new living environment, it is likely to reproduce uncontrollably. In 1988, several scallops (a mollusk similar to river clams) originally living in the European continent were brought to the North American continent by a cargo. At that time, these "stowaways" mixed in the cargo at the bottom of the warehouse did not attract the attention of the locals, and they were casually discarded in the waters near the Great Lakes. However, what is unexpected is that this place has become a "paradise" for clams. Without the constraints of natural enemies, the number of clams increased dramatically, and almost all the drainage pipes in the Great Lakes were "occupied" by them. So far, billions of dollars have been spent cleaning and replacing pipes. Longhorn beetles from Asia and red ants from South America are two other "invaders" that trouble Americans. The former destroys trees in Chicago and New York, while the latter bites people and animals and spreads diseases.

While "biological invaders" cause immeasurable economic losses to humans, they also pose a great threat to other species and species diversity in the invaded areas. During World War II, the brown tree snake settled in Guam on a military cargo ship. This tree-dwelling reptile specializes in preying on birds, raiding bird nests and devouring bird eggs. Since World War II, 9 of the 11 species of birds native to Guam have been driven to extinction by brown tree snakes. The numbers of the only two remaining species of birds are also decreasing day by day, and they are in danger of becoming extinct at any time. Some biologists saw brown tree snakes six times while flying from Guam to Hawaii Island. They warned that there are no natural enemies on Hawaiian Island that can inhibit the reproduction of brown tree snakes. Once brown tree snakes establish their home in Hawaii, the island's birds will be doomed. Many biologists and ecologists blame the increase of "biological invaders" on the increasingly prosperous international trade. In fact, many "biological invaders" take a "free ride" on transnational trade to achieve the purpose of "smuggling". Take the current global trade in fresh fruits and vegetables as an example. Many insects and insect eggs are attached to these goods, including extremely harmful pests such as Mediterranean fruit flies. Although the animal and plant quarantine centers of various countries take strict precautions against these pests, due to the huge volume of import and export goods, it is difficult to ensure that no "insects" slip through the net. In addition, transnational pet trade also provides convenience for "biological invaders". In recent years, reports of the introduction of colorful ornamental fish that have brought cholera to certain areas have frequently appeared in the press. Some pets from other places, such as snakes, lizards, bobcats, etc., often escape due to the owner's negligence or abandonment, causing harm to one party.

Some biologists point out that once a certain "biological invader" establishes a foothold in a new environment and reproduces on a large scale, its population will be difficult to control. Even today, when science and technology are highly developed, people will still be helpless in the face of animals and plants with extremely strong adaptability and reproductive capabilities.

Some scholars in biology and ecology argue that humans should not interfere too much in the migration process of biological species, because imbalance is temporary and a species must follow the law of natural selection in a new environment. . Not all "biological invaders" can survive. Those who can survive are the strong ones. Even the strong ones in the ecosystem are also restricted by various factors in the system and cannot do whatever they want. Therefore, the balance of nature will eventually be realized. However, more scholars hold opposing views. They believe that the process of natural regulation is very long. If "biological invaders" are allowed to develop freely, many native species will not escape extinction, and the species diversity of nature will be seriously damaged. In addition, the economic losses caused by "biological invaders" to human society are staggering. In the United States alone, the annual economic losses caused by "biological invaders" reach more than 200 billion U.S. dollars. Faced with such astronomical figures, how can people remain indifferent?

At present, many countries in the world have begun to realize the seriousness of this problem and have taken corresponding measures. For example, the U.S. House of Representatives passed a bill in 1996 requiring relevant agencies to strengthen monitoring of vehicles that may carry alien species. To this end, the U.S. government is preparing an interdepartmental monitoring plan.