Louisiana crayfish, USA
Whenever talking about "invasive species", there are always people on social networking sites who feel dismissive: those creatures that are regarded as flood beasts in other countries - such as the original crayfish, in our country, have become "spicy crayfish" accompanied by heavy seasonings, dominating the supper for many years; for example, the American bullfrog has become a regular customer in various cuisines such as hot pot in China... As if to put it this way, no matter which way the species invaded, in China, which is good at eating and drinking, can always be "eaten" to resolve.
Although the taste and creativity of Chinese food should not be underestimated, looking at invasive species in this way does have a little less seriousness. In fact, according to the 2019 Bulletin on the State of China's Ecology and Environment issued by the Ministry of Ecology and Environment in August 2020, more than 660 invasive alien species have been found throughout China. Among them, 71 species have caused or have potential threats to natural ecosystems and are included in the List of Invasive Alien Species in China. These "outsiders" hidden in the natural world often pose a serious threat to the local ecology and bring direct economic losses.
Invasive species, both in our country and around the world, have always been a headache.
From "Scavenger" to "Devil"
Remember the carp at home? In our impression, carp is a fat and auspicious name, and it is a delicious and allegorical ingredient for the New Year's Festival. But in the United States, carp is a nightmare existence.
The two major fingerlings of the flood, the silver carp and the silver silver carp, collectively known as the "Asian carp", breed wildly across the ocean, gradually engulfing the living space of local fish, and reducing the number of Spoon Sturgeon and Lake Sturgeon in Mississippi to being listed as endangered species – you know, they have an evolutionary history of hundreds of millions of years and have survived countless natural disasters.
Asian carp also invaded the Mississippi River, which affected all tributaries along North America's busiest commercial transport, the Golden Waterway. Whenever a transport ship passes by, the roar of the engine will frighten these carp, jump out of the water densely, and stage the lethal American version of the "carp jumping dragon gate": dense, large Asian carp fall on the ship like hailstones, often tragic incidents of smashing or even killing the crew. As a result, many passing boats will install barbed wire on board to prevent carp from "jumping".
As a very "famous" invasive species in the United States, how did the Asian carp make waves on the other side of the ocean?
The lethal American version of "Carp Leaping Dragon Gate"
Although the name "invader" is indeed a bit unjust for these species that have crossed the ocean to a strange natural environment and cannot defend themselves. Invasive species rarely choose to "leave their homeland" on their own initiative. Almost all invasive species that are internationally infamous and cause great devastation in non-native areas are introduced by human activities.
The Asian carp is one of the most striking examples. Before the flood and annoyance began, it actually had another name — scavenger.
The earliest Asian carp was placed on the high hope of a clean environment. In the 1960s, large numbers of aquatic plants and algae accidentally erupted in freshwater waters in the United States, affecting local ecology and the safety of passing vessels. The only way to control these floods of algae, and not to use chemical methods to avoid polluting water sources, is to fight them biologically. The "Asian carp" became the best choice at the time – they were highly viable and fed on both plankton and aquatic plants.
The United States took the initiative to introduce Asian carp and first released them in the southern state of Arkansas – the effect was immediate, asian carp "eat" the ring, and the annoying algae and aquatic plants almost disappeared. Since then, the United States has released Asian carp in the waters of different states, and they have also conscientiously exercised their duties as scavengers, until about 30 years after being introduced, the scavengers who were locked up for "work" accidentally got the opportunity to escape.
Failed introduction game
A heavy rain changed the radius of activity of the Asian carp. In this way, human activities are indeed difficult to blame for the "initiators" of invasive species, but the spread and proliferation of invasive species may also depend on the fuel of nature.
In 1993, there was a massive flood in Arkansas. The surging water became the best key, unshackling the scavengers and leaving them free to follow the flood out of the pond or captive river and drift everywhere. Invasive species have few natural enemies, and their superior reproductive ability has made Asian carp an overnight disaster in the United States.
If the original intention of the United States to introduce Asian carp was derived from practicality, but "the times are also lucky" and the yin and yang errors formed a disaster, then the African snail that flooded China can only be said to be a completely failed introduction game.
The African giant snail is not the weak and harmless native snail we think, but a "bully" that can grow to 20 centimeters, endanger nearly 500 crops, and can also nibble and digest cement.
African snail
The African giant snail originally lived in the far east of Africa, where it had a humid and hot environment suitable for its survival, and there were enough broad natural laws to dictate its habitat and reproduction— until human activity upset that balance.
In the process of the invasion of China by the African giant snail, we can see two patterns of invasion of a distant species under the influence of human activities: unintentional introduction and intentional introduction. Snails like to be dark and damp by nature, and have strong adhesion on the surface of objects, and with the trend of globalization, those ships and containers that cross the ocean, those trains and cars that are dusty and dusty, all give snails the opportunity to climb and invade.
But the scale of unintentional introduction is limited after all. The real impact is still human intention - the African giant snail has been intentionally introduced by some Chinese traders because of its beautiful appearance and delicious meat in the breeding state, and it has been raised into food or pets on a small scale. However, these folk breeding, extremely lack of isolation breeding technology and control capabilities, African snails soon left the breeding environment and began to breed in China.
The flooding of African snails does not even require a flood.
In the garbage heap of the city, on the crops of the countryside, vegetables, flowers, leaves, and even garbage paper and cement, it can be swallowed down, absorbing the elements in it to replenish energy. In addition, the African giant snail is hermaphrodite, with a strong reproductive opportunity and speed, a long lifespan, and likes to live in a dark place, day and night... All these bring difficulties to arrest and prevent. As a result, this alien species, which was once pinned on the "food" and "pet" expectations, completely broke away from people's control and became a complete "pest".
Eat, is it OK?
Since the purpose of the introduction is to eat, wouldn't it be okay to catch it and eat it? In fact, in the face of the flood of carp in the United States, people often ask the question of "why not eat it".
They have a common, simple answer – not tasty.
Because of the difference in cooking forms, for Americans, freshwater fish such as Asian carp are too troublesome to handle: those scraping, de-gilling, de-guts and other actions, it is difficult to adapt to the treatment of Western food, but also let the fishy smell of carp nowhere to hide; in addition, unlike marine fish, carp has more spines, and it is still too troublesome for Americans with knives and forks as the main tableware.
For Chinese, the African giant snail is not just a bad taste. The African snail, which lives in rotten soil and wet grass for its livelihood in garbage and cement, is almost a petri dish for bacteria. Pathogens such as nematodes and trematodes often use them as hosts. Don't say eat them, that is, the food and objects they crawl, the mucus left behind will leave a large number of pathogens, and touching them with bare hands can infect them with diseases - if you want to "eat" the way to prevent African large snails, you may pay the price of life.
American White Moth
In fact, most invasive species not only can't be solved by "eating", but even have no connection with "eating" at all – they are mostly insects, plants and microorganisms.
Please God is easy to send God hard. Of course, eating can not solve the problem, and the hasty use of poisons and other chemical agents will often "kill ten thousand enemies and damage three thousand", causing irreversible trauma to the ecological environment.
If you think differently, it may be a good choice to control the food chain in nature - let the natural enemies of invasive species eat it, and use biological control to "attack poison with poison". In the case of the control of African giant snails, it is always an important and green method to actively protect toads, frogs, ants and birds as much as possible, and to use their habitat to clamp down on the number of African large snails in the dark.
The silent biological control of moisturizers is indeed effective. Once upon a time, China was plagued by the American white moth — like the African giant snail, which crossed the ocean with the containers and timber of the global trade, was extremely fertile and resistant to chemicals. In Shaanxi, Chinese scientists have found a parasitic natural enemy of the American white moth and named it the white moth Zhou's little wasp.
This small bee is very small, specifically looking for the pupa parasitism of the American white moth, using a sharp egg layer to pierce the pupal shell of the American white moth, laying eggs inside its body, hatching into larvae, eating the tissues and organs in the parasitic American white moth pupa, the pupa continues to look for other American white moth pupa to parasitize, and the cycle has been repeated, and excellent results have been achieved. However, biological control is not a panacea, the introduction of false natural enemies will also bring uncontrollable harm, and the source of everything, human activities, cannot be completely stopped.
Combating species invasions is a long and trivial process. Effective prevention and control requires a multi-pronged approach, and intentional or unintentional introduction is only in the daytime. Eating will not solve the problem, but less enthusiasm for eating foreign species, more ecological awareness, may be as far as possible to reduce the serious consequences of species invasion, within the reach of human beings.
Author | Tao Kai
Edit | He Renyuan
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