Ecosystem is an acronym, that is, a word created by mixing two more words. Originally, it was an abbreviation for an ecological system, and is now the preferred term.
An ecosystem is simply an easy way to refer to all life forms (plant and animal) in a cohesive and relatively independent area, and their relationships to each other. In a perfect world, an ecosystem is in balance. That is, predatory species control the population of prey species without completely destroying them, and vegetation remains varied without one type predominating and expelling the others.
Ecosystems are rarely in balance, which is often alarming. For example, the runoff of pollution from a factory can affect the marine life of a lake, causing the fish population to fall. This destabilizes the entire surrounding ecosystem, and birds and animals that feed on fish die or migrate to areas with more food.
Trying to counteract the damage to an ecosystem requires a complete understanding of all the interrelationships between plants, animals, and the atmosphere of the system. Because such a perfect understanding is seldom possible, it often has unintended consequences.
For example, the U.S. government recommended in the 1930s that southern farmers plant kudzu as a ground cover to help prevent erosion. Now, kudzu is a harmful plant and thousands of hours a year are spent trying to prevent kudzu from taking over, damaging roads and buildings and drowning other plant species. A similar takeover of a non-native species is seen in the rabbit problem in Australia. Rabbits do not have a natural predator native to Australia. Thus, when introduced in the 19th century, they proliferated like, well, rabbits, to the point that their effects on the ecosystem, especially farmland, were devastating.
In nature, no ecosystem can be considered independent of neighboring ecosystems or even the global ecosystem, because ecosystems are open and plants and animals can move between them. All ecosystems are affected by planetary trends that affect the atmosphere, such as pollution and global warming.
An attempt to study an isolated ecosystem was Biosphere 2, an airtight enclosure that attempted to duplicate an ecosystem in equilibrium. Although the experiment was unsuccessful (they could not keep oxygen levels high enough for human health regardless), the experiment made it clear how well an ecosystem is balanced, it is fragile. and how dangerous it can be to severely damage the Earth’s ecosystem.