The objectives of ecological restoration in the disaster area are to restore the soil and vegetation in the damaged area, ensure that the restored soil has a certain degree of fertility and vegetation cover; increase the number of plant and animal species, restore the regional biodiversity and ecological communities, and improve the self-sustainability and production capacity of the ecosystem; minimize and deal with ecological pollution, increase the visual aesthetics, and reduce the risk of the ecological environment; and restore or even increase the stability of the ecosystem and maintain the continuous succession and development of the ecosystem. In the disaster area, the ecological environment damage is much more complex.
(1) The area of loss of forest land and forest stock is huge, and the forest biological chain is out of balance, so there is an urgent need to rebuild the forest cover system and restore the ecological function of forests.
(2) Prevent secondary geologic disasters. The areas of frequent geological activities in the southwest of China are mainly concentrated near the fracture zones. These areas have special topography, complex geological structure, unstable geological structure, steep slopes, deep ditches and many canyons. Earthquakes are prone to aggravate geological disasters such as landslides and mudslides. Various geologic disasters damage cultivated land, with extremely deep damage and large areas of damage. Geological action changes the original appearance of the mountains and rivers, which is a normal growth activity of the earth, we can not completely prevent the occurrence of natural disasters, but we can try to minimize the extent of its destruction, to minimize the loss.
(3) Eliminate the hidden danger of water environment safety. Southwest China is in the first and second terraces in China's topographic plate, the terrain is higher, is the birthplace of many rivers. The region is controlled by the subtropical high pressure, and by the Indian Ocean and the North Pacific Ocean air currents, warm and humid air flow through the plains in the southeast directly inland, is hindered by the tall Longmen Mountains, mountainous terrain on the air flow to play a role in uplifting the air flow to promote the vertical movement of the air, and the low altitude temperatures, the ground temperature is high, the condensation of water vapor in the air to form rain. The sparse geology of the region, coupled with the high mountainous and hilly terrain and dense waterways, makes it easier for flash floods to erupt during heavy rains. After flash floods, sediment and accumulated materials on both sides of the river enter the water body with the rain, causing siltation of the river, a decrease in the self-purification capacity of the water body, and a deterioration of the water quality. The disinfectants, sterilizers and pesticides used in large quantities in post-disaster epidemic prevention work, as well as the large quantities of medical waste, domestic garbage and domestic sewage that could not be disposed of in time at the resettlement sites of the victims, objectively will also pollute the water bodies. At the same time, the town sewage, garbage treatment and other facilities are seriously damaged, greatly reducing the ability to treat pollution; chemical plant damage, resulting in chemical leakage, all to the water environment, causing serious safety hazards.
(4) Restoring the ecological balance of nature reserves. Areas where natural disasters occur are often rich in geological landscapes and even contain some nature reserves. For example, Aba Prefecture in Sichuan Province is an important ecological barrier in the upper reaches of the Yangtze and Yellow Rivers, and is the core area of ecological protection in China, with a number of national and provincial nature reserves such as Jiuzhaigou, Huanglong, Wolong, and Siguniangshan. After the Wenchuan earthquake, the roads leading to these nature reserves were broken and blocked, and the ecological environment and various facilities in the nature reserves were damaged to varying degrees, with the Wolong and Four Girls Mountains nature reserves almost devastated. Therefore, in the work of restoring the ecological balance of the nature reserves, more consideration should be given to the unfavorable factors, so as to provide a safe and stable place for the animals and plants to live in the future.
(5) Rebuilding regional ecological functions. Natural disasters have caused the decline of regional ecological function, and a large number of dominant and endemic species that have been naturally selected in the region over the years have died out, and the biodiversity of the region has weakened. The goal of ecological restoration should give more consideration to water conservation, soil and water conservation, reasonable placement of plant and animal species, guaranteeing the supply of agricultural and forestry products, and improving the regional habitat.
When ecological restoration of the disaster-damaged land is carried out, it should be considered from three levels:
(1) Population level. Ecological restoration must put the disaster-damaged area in a semi-natural state capable of self-repair, which also applies to the restoration of animal communities. The requirements for plant and animal community restoration are very similar in that the end product of their restoration must be a population or community that is self-sustaining.
(2) Species level. The ideas of evolution and genetics have always influenced modern ecological restoration. Those marginal disciplines related to ecology that emphasize function and process have been well complemented by the development of the basic science of ecology. The modern model of ecological restoration focuses more on the restoration of species' habitats and communities than on the restoration of the functioning of the destroyed ecosystems, and this restoration involves genetic and evolutionary processes, which result in the extinction of species and the formation of new species through continuous natural selection and survival of the fittest. Therefore, in the ecological restoration of disaster-damaged land, it is necessary to consider not only the species suitable for survival, but also the problems faced in the future of evolution over time and the introduction of genetic diversity of species.
(3) Landscape level. At present, people's goals for ecological restoration of disaster-damaged land are more focused on engineering measures and management, with the aim of restoring the ecological environment of the damaged area as soon as possible. But the region where the natural landscape structure has been changed after the disaster, the ecology of recovery should be studied from the landscape level. The awareness of the importance of ecological restoration at the landscape and regional levels is increasing, but ecological restoration at the landscape level is still at an early stage and needs time to be studied.