What are the three invasion ways of biological invasion?

The process of biological invasion in nature is quite slow. But with the help of human beings, an invasion that may take thousands of years can be completed in one day. The research on the invasion mode of alien species shows that the invasion is mainly achieved through conscious introduction, unconscious introduction and natural invasion.

natural invasion

natural invasion refers to the expansion of natural distribution areas without human influence at all. It is the main way of natural invasion to spread weed seeds through the natural introduction of wind and water and the migration of birds and other animals. For example, Mikania micrantha may be introduced into Guangdong from Southeast Asia by airflow, and rice field weevil beetles may also be transported to China by airflow.

unconscious introduction

Many alien invasive organisms were introduced unintentionally with human activities. Usually, people or products are introduced to a new environment as "stowaways" or "hitchhikers" by planes, ships, trains, cars and other means of transportation. With the continuous increase of international trade, the continuous expansion of foreign exchanges and the rapid warming of international tourism, alien invasive organisms have been introduced into China more and more through these channels. 1. Enter with human vehicles. Many alien species enter and spread with traffic routes, and the vegetation around roads and railways is usually destroyed and degraded, which makes these places the earliest or frequent places for alien species. For example, ragweed mostly occurs on both sides of railways and highways, and was originally introduced from North Korea by train; Rattus norvegicus and Rattus flavipectus in Xinjiang were also introduced from the mainland by railway. 2. Ship carrying. When an ocean-going freighter leaves the shore empty, it needs to be filled with ballast water, and when it is loaded in different places, it needs to be discharged, and a large number of creatures move to different places with ballast water, which leads to seawater pollution and biological invasion. There are about 16 species of harmful red tide organisms in China's coastal waters, most of which are introduced through ballast water. 3. Marine garbage. More and more wastes are discharged into the ocean by human beings, and the floating marine life adsorbed on the waste wastes flows around the world and invades these countries and regions, thus posing a threat to the invasive species. For example, marine garbage has doubled the number of organisms that spread to subtropical areas, and even more than doubled in high latitudes. 4. With the import of agricultural products and goods, many alien invasive species are brought in with the introduction of other species. For example, a large number of weed seeds are imported with grain, poisonous wheat is introduced into China with wheat introduction, and some forestry pests come with wooden packaging materials. 5. Bring it with tourists. With the opening of the international tourism market, transnational tourism is increasing. Living organisms carried by tourists in different places, such as fruits, vegetables or pets, may carry dangerous alien invasive species. China's customs has repeatedly seized Mediterranean fruit flies from the fruits carried by entry personnel. In addition, some species may be brought into China by the adhesion of tourists' luggage.

Soap grass humans introduce new species or varieties for a certain purpose, so that a species can be purposefully transferred to areas beyond its natural distribution range and diffusion potential. China is a country deeply invaded by alien species, and one of the most fundamental reasons is that China is a country that introduces the most foreign species. China has a long history of introduction, and it has a long history of introducing excellent varieties from other places or abroad. Early introduction was often achieved through ethnic migration and trade between regions. With the economic development and reform and opening up, there are a large number of introduction projects of foreign species in almost all units related to breeding, breeding and planting. Due to the over-belief that "foreign monks can recite the scriptures", there are some blindness, disorder and shortsightedness in the introduction in China, which leads to a large number of biological invasion incidents. Among the known alien harmful plants in China, more than 5% species are the result of artificial introduction.

Intentional introduction has various purposes, which can be divided into the following aspects: 1. Introduction as pasture, feed or human food. Such as Alternanthera philoxeroides (also known as Alternanthera philoxeroides), purple alfalfa and Eichhornia crassipes introduced as pasture and feed; Apricot, amaranth and sunflower introduced as vegetables; Guava and egg fruit introduced as fruits; As food animals, the big bottle snail, the brown cloud agate snail, etc. 2. Introduced as an ornamental creature. Curiosity psychology makes people constantly introduce animals and plants from outside the local area as ornamental plants or pets. When these creatures escape or are abandoned in the wild, they may become dangerous alien invasive species, such as Solidago canadensis, mimosa, Oxalis rubra and piranha. 3. Introduced as a medicinal plant. Most of traditional Chinese medicine in China is native to China, and some of them are exotic species, some of which have become invasive species, such as soapwort, talinum, Phytolacca acinosa, Datura flower and so on. 4. Introduction as a plant to improve the environment. For example, in order to repair the damaged environment, human beings treat some characteristics of alien species unilaterally and introduce some dangerous alien species. Such as Spartina alterniflora and Mikania micrantha.