People have become a major component of the nutrient cycles both through agriculture and other activities. Typically, agricultural ecosystems export nutrients, both as crop and through drainage. These losses have to be made up by the import of fertilizers. Ecological succession Nutrient cycling and trophic levels involve processes occurring all of the time in ecosystems. There are also long term changes in vegetation that we know as succession.
Clearance also occurs in nature through floods, storms, earthquakes, and fires.
The early years will likely show a rapid change of vegetation until a more stable ecosystem develops. Early ecologists thought that this would be a climax community of plants and animals characteristic of the area. However, the process of succession may never stop and the mix of plants present at any time is unpredictable. It may be that with small scale disturbance original vegetation will recolonize an area. Succession is a real process, even if climax communities do not exist.