Ecological succession may also occur when the circumstances of an environment change abruptly and dramatically. Forest fires, windstorms, and human activities such as agriculture all have a significant impact on the ecosystem. As a result of these changes, the original species living in the area are replaced by new ones.
Abrupt changes in environmental conditions can cause extinction debt. Extinction debt is the delay before the ecosystem recovers after a major disturbance. The more widespread or intense the disturbance, the longer it takes to recover fully. For example, following a forest fire, the tree seed bank is depleted, so recovery depends on new seeds germinating and growing quickly enough to out-compete the older trees. If the fire was very severe, such as if it burned through all the dead wood under the live trees, then this process would take much longer than if the fire had only burned through some of the dead wood.
After an asteroid impacts Earth and creates a lake called the Chicxulub crater, ecological succession occurs rapidly. Within 10,000 years, forests have reestablished themselves across most of what was once dry land. The only areas where no trees grow today are around the margins of the lake where there is not enough sunlight for trees to thrive.
Plants and animals will return to the region in a process known as ecological succession. The steady change in the structure and makeup of an ecological community through time is referred to as succession. This can occur in areas where an established ecosystem has been devastated by a disturbance. For example, the area may have been burned over when fire was allowed to go unchecked. Natural regeneration will bring new species to dominate the scene, replacing those that were lost. As another example, an area used for pasture might be cleared of all its vegetation and then allowed to go back to forest.
Succession is also important in ecosystems where there is no clear-cut end point to a disturbance. For instance, if a tree falls in a forest and destroys another tree's roots, it can lead to more trees falling over in future because they cannot support their weight. If a landslide covers some grassland with soil from its base down, then new plants will grow up from the covered rock which will eventually replace the turf. Succession is also relevant to human-made landscapes such as gardens and parks. Here, we try to keep trees and other plants around for as long as possible by taking care of them. But even in a garden or park that receives regular maintenance, old plants will be removed from time to time as they become too big or ugly for visitors to enjoy.
Old plants will be replaced by new ones as soon as they are gone.
Succession Although these changes can occur fast in some circumstances, in most cases, species gradually replace others, resulting in long-term changes in ecosystems. These long-term, progressive alterations in changed ecosystems are referred to as ecological successions. Ecosystems fluctuate over time until a stable system emerges. As one component becomes extinct, another group of organisms replaces it.
For example, the dinosaurs became extinct about 66 million years ago, and modern birds have been evolving since then. However, it can take hundreds of years for all the members of a single species to go extinct, because new species often evolve that are able to live in the same place and feed on the same kinds of foods. This is why geologists can tell how many different species were living in an area at any given time by looking at the layers of rock that contain their fossils. Over time, they say, will reveal the story of life in the area.
Some species may even become so dominant that they affect the evolution of other species nearby. For example, if there are no other fish around when a young shark comes into the ocean, it may grow up to be a top predator that prevents other fish species from evolving larger bodies or developing teeth, because it would be eaten anyway. In this way, the young shark's death may have helped create conditions that allowed more advanced fish to survive and reproduce.
An example of succession in action is found in tropical rainforests.