Ecological restoration is the systematic process of restoring an ecosystem or habitat back to its original state after it has undergone any kind of disturbance. It is an intentional activity introduced in an ecosystem to accelerate the recovery of the overall ecosystem in terms of health, sustainability and integrity. A large variety of ecological processes can be done to restore an ecosystem like afforestation, daylight streams,reintroduction of native species, removal of non native species, habitat and range improvement of targeted species, removal of weeds and revegetation of arid areas. There are a lot of factors that underpin the requirement of ecological restoration, and why it is the need of the hour in so many ecologically critical environments. Some of these are listed below.
Disturbance is a change in the ecosystem that can potentially cause short term or long term harm to it. It can occur at many scales and at different levels of severity. Some are natural parts of every ecosystem. They can potentially bring about major changes like species composition, soil properties and even changes in nutrient cycling. Natural disturbances include volcanic eruptions, tree falls, floods, forest fires, severe weather damage etc. Anthropogenic disturbances are much more common and more devastating in impact. They may include clearing land for agriculture, building a dam etc. The restoration process aims at speeding up the recovery process after a disturbance has taken place in a ecosystem.
Plants and animals that were present before the disturbance occurred, and are local to the ecosystem are highly likely to be well adapted to it. Therefore, one way of bringing back order and normalcy to the ecosystem is to use plant and animal materials collected from local sources and relocate them there in larger numbers. The greater the number of plants and animals included, the greater the biodiversity, and greater the chance of bouncing back after a disturbance. The native plants and animals are also quite adept at fighting off foreign invaders if they have larger numbers, and if they are spread across a larger ecological landscape.
Ecological succession is the methodical process of accelerating the bouncing back of an ecosystem after it has gone through a disturbance event. There are two types of successions possible: active succession and passive succession. Passive succession simply refers to the natural succession of the ecosystem by removing the source of the disturbance. Example of a passive restoration is the recovery of the deciduous forests in the eastern United States after the abandonment of agriculture. Active restoration involves accelerating the rate of recovery of the ecosystem by changing the trajectory of succession. Mine tailings would take decades longer to recover from if not for active restoration.