An ecosystem refers to a system in which all animals, plants, microorganisms, and inorganic environments in a certain area are maintained through interactions. All ecosystems are mainly divided into biological and non-biological members. The former can be classified into producers, consumers, and decomposers. The latter refers to the environment itself. The basis of the biological members that make up an ecosystem is the individual. In nature, there are groups of organisms that are morphologically and reproductively distinguished from other individuals, which are called species. Mutual reproduction is possible between individuals of the same species. As individuals of each species have the same food, habitat, and environmental requirements, they form a herd in a specific area, which is called a population. A population is a dynamic group whose size, age structure, and gene pool change according to environmental variations, and has different properties from the individual level. There is no clear boundary between populations. Usually, several types of populations coexist in one region; this unit is called a community. Communities and non-biological members are called an ecosystem.

If you look inside an ecosystem, you will always see organisms that grow using photosynthesis - in some cases, chemical synthesis - and provide food to other organisms. There are also decomposers that recycle the basic elements of life. Ecosystems can perfectly circulate essential nutrients such as carbon, nitrogen, oxygen, phosphorus, and sulfur. In an ecosystem, nutrients are recycled by starting from a life and returning to a new life going through organic waste and pollutants. During this process, energy flows in in the form of sunlight, wind, and water and then flows out in the form of heat.

The stability of ecosystems is also related to species diversity. Species diversity is measured by the number of species and the population of each species; it is high in a mature community, i.e., a climax community, and it is generally considered that the higher the species diversity, the more stable the community. For example, very complex ecosystems, such as rainforests, remain permanently unchanged without human disturbance. However, in simple ecosystems with only a few species, such as a tundra, the size of a population tends to significantly change according to environmental variations. In artificially simplified arable land, the ecosystem may be destroyed, if biological or non-biological factors change significantly. This shows that the complexity of an ecosystem is directly related to its stability.

Take the food web of simple and complex ecosystems as an example. The food web of a mature ecosystem involves a lot of interactions between organisms; even if one species is removed, it will not affect the equilibrium of the ecosystem. In contrast, in a simple ecosystem, the number of constituent species is small. Therefore, if any of the species is removed, the effects can spread throughout the ecosystem.

On the other hand, some argue that the relationship between ecosystem stability and species diversity is unclear. They insist that the high stability of rainforest ecosystems is not because of high species diversity but the absence of climate change, and the low stability of tundra is due to severe climate change. It is not clear which argument is correct, but what we can be sure of is that simplifying the constituent species of an ecosystem can be fatal for maintaining its structure and function. With the increasing population and the development of industries, the natural ecosystem has become simpler, leading to the low stability of the ecosystem. The more species an ecosystem has, the greater its biodiversity. When the number of species decreases, we say that ecosystems are poor. Ecological poverty occurs when a meadow full of dozens of grasses and flowers, hundreds of insects, birds, and small mammals, and innumerable microbes turns into a city or suburb. In such areas filled with roads and buildings, rats, pigeons, sparrows, a few kinds of trees, and cockroaches - species that have figured out how to live with humans – are mostly populated.

Source: Eco-generation Korean Website