Summer is here and the season to eat crayfish is here again!
This can be called the "carry handle" of the supper industry, do you know that it is an imported product?
Crayfish, scientific name "Protocrawfish", native to the southern United States and northern Mexico, introduced to Japan by the United States in 1918, and then introduced to China by Japan in 1929, and has become an important economic breed in China in recent years.
Crayfish and tilapia are both relatively successful introductions in China. A small number of exotic aquatic animals and plants have become important fishery economic species in China, but more exotic aquatic animals and plants are harmful to the ecological environment and economic development. Due to the lack of a full assessment of its risks in the process of introduction, coupled with the escape of aquaculture, the discarding of aquariums and the random release of aquatic species, the current situation of biological invasion has been formed, and china's aquatic ecosystems have also suffered great pressure.
With regard to the definition of alien species, the definition given by the IUCN Species Survival Committee (SSC) in 2000 is defined as "alien species as species, subspecies or taxa that appear outside the natural range and potential for dispersion in the past or present", which is simply defined as "species introduced from a region or country from abroad that have not been historically distributed." ”
The introduction of wheat, corn, potatoes and other major crops has greatly enriched people's dietary nutrition structure while meeting the growing food needs of human beings, effectively increasing the output of land, and achieving rapid population growth in many periods.
There are two sides to everything, and while introducing alien species to promote agricultural progress, the invasion of alien species has become one of the serious problems facing the world. Among them, exotic aquatic animals and plants are a major taxon. Of the world's 100 most threatening invasive alien species, 25 are aquatic plants and animals.
The World Union for Conservation of Nature (IUCN) lists 100 of the world's most threatening invasive alien species
China's vast territory, complex geographical and climatic conditions, and a wide variety of water ecosystem types, including oceans, rivers, lakes, reservoirs, wetlands, etc., not only nurture rich aquatic biological resources, but also provide excellent natural resources and environmental conditions for the introduction, survival and reproduction of exotic aquatic animals and plants.
Since the 1980s, after the focus of fishery development has shifted from fishing to aquaculture, China has actively introduced exotic aquatic animals and plants, which have played an important role in improving the structure of aquatic products in China and enriching people's diet and leisure culture, such as Turbot (Multi-treasure Fish), Protocrayfish (Crayfish), Tilapia, Spotted Forktail Catfish, etc. While exotic aquatic animals and plants have brought new economic growth points to aquatic products, some species have also brought hidden dangers to ecosystem security, such as Fushou snails have become an important pest in worldwide agricultural production, which will not only have a serious impact on food production, but also seriously damage local aquatic biodiversity.
Crayfish, an exotic species that bring great economic benefits
Fushou snail, an invasive alien species under national key supervision
Alien species invasion is the second cause of biodiversity loss after ecological and environmental persecution, which poses a threat to the global environment and biodiversity conservation.
After the introduction of an alien species, it may be excluded from the system because it cannot adapt to the new environment; it may also be that because there is no organism in the new environment to compete with or restrict it, the introduced species may become a real invader, upsetting the balance, changing or destroying the local ecological environment.
Three prerequisites for the formation of alien species invasions
(1) It must be an alien species. How to judge mainly depends on whether there are records of the distribution of this species in history.
(2) This species can survive and reproduce under the ecological environment entered, forming a population with alternating generations.
(3) It is harmful to the local ecosystem, can change or damage the ecosystem, threaten the biodiversity of the ecosystem, and even cause socio-economic losses and threaten human health. Those who do not meet this condition can only be called alien species, not invasive alien species.
The Global Assessment of Biodiversity and Ecosystem Services released by the United Nations in May 2019 notes that the number of invasive alien species in each country has increased by about 70% since 1970, and that alien invasions have become one of the five major factors that have had a serious impact on global ecosystems over the past 50 years, and are often less concerned, valued and controlled than other factors such as habitat destruction, overfishing, climate change and environmental pollution.
Fushou snail eggs multiply on rice Source: @ Put the wine to laugh
In addition, what is more serious is that the invasion of alien species can cause serious damage to the ecological environment, and can have an impact on individuals, genetics, populations, communities, ecosystems and other levels, resulting in endangered species and extinction.
Due to the lack of adequate early warning and prevention of foreign biological invasions in society, coupled with the unscientific and irregular social release behavior, the spread of some exotic aquatic animals and plants to natural waters may have adverse effects on China's aquatic biodiversity and water ecological environment. At present, some harmful alien species have been included in the scope of national key supervision or are clearly listed as "invasive alien species" (such as hollow lotus grass, hyacinth, huhua rice grass, Fushou snail, Nystemporum carp, bullfrog, etc.).
In recent years, the alien species invading China are showing such undesirable trends as an increase in the number of imports, an acceleration in the frequency of introduction, an expansion of the scope of spread, an aggravation of harm, and an aggravation of economic losses.
Spotted eel
Comparison of hollow lotus grass and its approximate species
Regarding the relationship between man and nature, Engels once said: "Let us not be too intoxicated by our victory over nature." For every such victory, nature has retaliated against us. Each victory, in the first step, does achieve the result we expected, but in the second and third steps it has a completely different and unexpected effect, often canceling the first result again. ”
Man is always a part of nature, and with the establishment of a community of common destiny, human beings must learn to live in harmony with nature.
Classification and implementation of policies, rational use of the beneficial side of alien species, effective control of their harmful side, the national biosecurity needs you and me to jointly protect!