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Alien species management

Alien species are introduced by human activities intentionally or unintentionally, and plants in nature slowly invade other ecosystems or spread out through natural (such as animals, wind, water, etc.) media to form species invasions, and in natural or semi-natural ecosystems or Establishing its own dominant population in the habitat changes or threatens the original local biodiversity. There are more than 100 invasive species recognized in the world that have caused harm. The invasion of alien species has severely affected biodiversity, genetic diversity, ecosystem diversity, and ecological service functions. For example, the snails in the south, Spartina spartina in the east coast, Mikania in the south China, Eupatorium adenophorum in the southwest, and Solanum sinensis in Inner Mongolia and the northeast. These invasive alien species are widely distributed in farmland, grassland, lakes, rivers, etc. Almost all ecosystems such as wetlands and forests threaten our country's ecological security, biological security, economic security, food security and human health.

The wetland ecosystem is also facing the invasion and destruction of alien species. Due to the fragility and complexity of the wetland ecosystem, the harm caused by invasive alien organisms will be amplified through energy flow, food chain, material circulation and other links, thereby affecting the entire wetland ecosystem. Once the wetland ecosystem is invaded by foreign species, the structure and function changes will be difficult to repair. For a stable wetland ecosystem, the process of alien biological invasion is short-lived, but the work to repair the damaged wetland ecosystem and biodiversity is long-term. The harm caused by invasive species is obvious, its potential danger harmful nature unpredictable.


Spartina alterniflora invasion

Preventive measures

Manual control

Rely on manpower to catch foreign pests or pull up exotic plants. Artificial control is suitable for those invasive species that have just been introduced and settled but have not yet spread on a large scale. China is rich in human resources, and manual control can quickly remove harmful organisms in a short time, but it can do nothing about plant seeds and some harmful animals that have sunk into water and soil; high-fertility harmful plants are easy to grow and spread again, and it takes years Prevention and control: After artificial control of harmful animals and plants, if animal and plant residues (body, such as eggs) are not properly treated, they may become new sources of transmission, which objectively accelerates the spread of alien organisms.

Mechanical removal

Use specially designed and manufactured machinery and equipment to prevent and control harmful plants. Mechanical control of harmful plants is safe for the environment, and can quickly kill exotic plants within a certain range in a short period of time. The use of mechanical salvage boats to control water hyacinth and other aquatic weeds has achieved certain results in Lake Victoria and other places in Africa. Kunming, Yunnan, China also designed and manufactured a mechanical salvage boat to remove water hyacinth in Dianchi Lake, and Fujian Agricultural University also helped design and manufacture a "mower" to control rice grass in Ningde, Fujian, but they were ultimately unsuccessful due to technical reasons. In addition to technical problems, after mechanical control, if harmful plant stubs are not properly treated, these stubs may become a new source of transmission depending on asexual reproduction. It is also possible to control foreign pests through various methods of physics, such as using fire to control harmful plants, black light lamps to trap harmful insects, and so on.

Alternative control

Substitution control is mainly aimed at alien plants, which is an ecological control method. Its core is to replace invasive alien plants with native plants with economic or ecological value according to the own law of plant community succession. Its advantages are:

Once the replacement control plants are planted, they can control invasive plants for a long time, without the need to control them year after year;

Substitute plants can maintain water and soil, improve soil, conserve water, and improve environmental quality;

Alternative plants have direct economic value, can recover planting costs in the short term and benefit in the long term;

Substituting plants can turn barren land into economic land and improve land utilization.

The disadvantage of alternative control lies in the higher environmental requirements. Many habitats are not suitable for artificial planting of plants, such as steep mountains and waters. At the same time, artificial planting of local plants involves many ecological factors to restore the natural ecological environment. A certain degree of difficulty. To study the use of alternative plants to control exotic harmful plants, we should fully study the biological and ecological characteristics of native soil plants, such as their competitiveness with invasive plants, and other effects, etc., master the technical points of reproduction and cultivation of these plants, and explore the characteristics of native plants Economic characteristics, market potential, etc. in order to obtain economic and ecological benefits at the same time. Shenyang Agricultural University and the Liaoning Provincial Highway Administration jointly established a 200h㎡ ragweed alternative control demonstration area on both sides of the two expressways, Shenyang-Dalian and Shentao, in 1989 and 1990. The selected alternative plants include Amorpha pseudoacacia The biomass of Ambrosia trifida was reduced from 30kg per square meter to 0.2kg per square meter after the completion of the demonstration area, and the biomass of these alternative plants are still in feed, green manure, Food, medicine, basket-weaving materials, energy and chemical raw materials have brought huge economic benefits.

Biological control

Biological control refers to the introduction of food-specific natural enemies from the origin of foreign pests to control the population density of pests below the level of ecological and economic harm, similar to the self-regulation of the ecosystem. The basic principle of the biological control method is based on the ecological balance theory of pests and natural enemies. In the place where the pests are introduced, the natural enemy factor of the place of origin is introduced to re-establish the mutual adjustment and mutual restraint mechanism between the pests and natural enemies to restore and maintain. This ecological balance. Therefore, biological control can achieve the result of using biological diversity to protect biological diversity.

The general working procedures of biological control include: inspection and collection of natural enemies in the place of origin; safety evaluation of natural enemies; introduction and quarantine; research on biological ecological characteristics of natural enemies; release and effect evaluation of natural enemies. Because once natural enemies establish a population in a new habitat, they may rely on self-reproduction and self-proliferation to control pests for a long time. Therefore, biological control has the advantages of long-lasting control effect and relatively low control cost.

In addition, the introduction of natural enemies to prevent and control alien pests also has a certain ecological risk. If the natural enemies are not released through careful and scientific risk analysis, the introduced natural enemies are likely to become new alien invasive organisms, which will bring about the consequences of "introducing wolves into the house". . The international biological control of weeds has a history of more than 100 years. While the introduction of natural enemies to control weeds has made achievements, it is also facing new challenges such as the safety of natural enemies. The natural enemy insect Cactoblastis cactorum has successfully controlled Opuntia spp. in Australia, South Africa, Hawaii and other places , but in 1989, Florida discovered that the insect threatened a local flower plant cactus and became a serious pest.

In 1993, FAO promulgated the "International Convention on the Management of Introduction of Natural Enemies for Biological Control", which regulated the introduction of natural enemies. Before the release of natural enemies by biological control of harmful plants in the world, the safety of natural enemies is tested. The main methods are selective and non-selective. The types of plants tested for risk analysis include the following categories:

  • Taxonomically, the representative species of the same family or related family as the target plant;

  • Representative species of important local economic and ornamental crops;

  • Locally endangered species;

  • Species similar in morphology and phenology to the target species.

Comprehensive governance

Combining individual technologies such as biology, chemistry, machinery, manpower, and substitution to give full play to their respective advantages and make up for their own shortcomings to achieve the purpose of comprehensive control of invading organisms. This is a comprehensive treatment technology. Comprehensive governance is not a simple addition of various technologies, but their organic integration, mutual coordination and mutual promotion. Taking the use of biological and chemical control to comprehensively control invasive plants as an example, as it combines the advantages of chemical and biological control and at the same time makes up for their own shortcomings, it has the following characteristics:

Quick result in the early implementation, in some places the urgent need to get rid of harmful plants, the selective use of certain varieties and herbicide doses to suppress the rapid proliferation of harmful plant populations in the short term spread, thus speeding up the control speed;

Sustainability Because herbicides can only achieve short-term control effects and are difficult to last, after the herbicides are used, a certain number of natural enemy insects that specialize on harmful plants will be released and established populations to settle, long-term self-reproduction, and gradually reach and maintain plants -Population dynamic balance among natural enemies to achieve continuous control results;

Safety compared to a single application of chemical herbicides, varieties comprehensive management of chemical herbicides, concentration, dosage and number of applications have strict restrictions, selected herbicides on other biological safety, concentration, dose, frequency are It is much lower than the conventional dosage, so it has high safety and little impact on the environment;

The economic comprehensive treatment technology system is mainly based on biological control. After the natural enemies are released, the natural enemies can reproduce themselves and establish a population. After reaching a certain number, there is basically no need for artificial proliferation. Therefore, it has the advantages of one-time investment and long-term results, and the cost of prevention and control relatively low.