Over time, ecosystems can alter a great deal. The climate of the Earth has gradually changed many times even within the time when records have been kept. Before that we know that parts of the world experienced Ice Ages, which had huge effects on the environments of living things. Human beings also alter ecosystems, often without realizing the possible results of their actions. Once large areas of North America and Europe were covered with deciduous woodland. Over hundreds of years, trees have been cut down for building, to supply fuel and to clear land for farming, so that remaining areas of woodland are comparatively small.
Whether just starting out or full of life, ecosystems are constantly changing. The process in which they are changing is called succession. Succession comes in two forms: primary and secondary. Primary succession is “the series of community changes which occur on an entirely new habitat which has never been colonized before.” These changes occur in places like area of cooled down lava, sandy areas and chiseled out rock faces.
Secondary succession is “the series of community changes which take place on a previously colonized, but disturbed or damaged habitat.” These places involve areas damaged by fires, floods, or areas where the trees have been cut down. These disturbances have not taken away all forms of life and nutrients from the area. If succession is done in a proper way, the ecosystem can become a climax community in which the ecosystem stabilizes. The process in becoming a climax community can take either a short or long time which differs from area to area. There can also be times which it is set back a few stages, like when trees are cut down. This sets the area back some, but it can still grow back and still become a climax community. The climax is stabilized by a small community of prominent species. The web of biotic interaction that a climax community creates is so intimate that an introduction of a new species could disrupt the stabilization. If a new species were to be introduced, it could cause one species to become too dominant. However, this ecosystem would be more diverse. This loss of stabilization could easily be called a disturbance.
A disturbance is a mixture of large, infrequent and small frequent events and they can occur from the result of numerous, interconnected factors. Disturbances are categorized by type, severity, intensity, frequency, and timing. The word disturbance makes it seem like it has a negative effect on ecosystems, but the opposite is true. For example, most natural disturbances help renew ecosystems and diversify the landscapes. As stated earlier, they often lead to ecological succession. However, anthropogenic disturbances, ones related to humans, often have negative effects. For example, if humans introduce invasive species into the environment, they can hunt and prey on native species and disrupt the ecosystem’s stability.
Within each type of succession is a stage. These stages include pioneer, establishing, sustaining, and producing. Each of these are found in the types of succession, but are not necessarily in only one. The pioneer stage is usually in primary succession. This stage brings new life to area where there is none. It is and creature or plant that starts to grow or live there. It is the start of the ecosystem. This next stage is very similar to the pioneer stage. The establishing stage is when animals or plants find things that sustain their lives and allows them to live in the area. The sustaining stage is usually in the climax succession. It is when the area can sustain life and allows life to continue in the area. The animals also do not have to leave in order to find food. The other stage is the producing stage. This is usually during the secondary succession. It happens when the population of animals is growing but many drift to other places in search for food. These places can sustain life but at a limited population. These types of succession, the stages and the disturbances that cause them all create and change and ecosystem though the years.
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