Earth has a wide variety of ecosystems that maintain its function and make it wondrous. While most of us are familiar with the term “ecosystem”, a lot of people may be unsure about what that term actually means. And that’s understandable — several different definitions are often used for the same term. However, the best all-encompassing definition for an ecosystem is all of the living organisms (plants, animals, and bacteria) and the nonliving components (air, water, soil, weather) that interact with each other as a system. The size of an ecosystem can range from a small tide pool to a giant desert. All the members of the system are interconnected, so the loss or change of one factor can have large effects rippling through the entire ecosystem.
External and internal factors
Energy enters an ecosystem from the sun, which plants utilize, as well as carbon dioxide, which is used for photosynthesis. Animals eat the plants, moving the energy and matter through the ecosystem. When organic matter dies, decomposers break it down, releasing carbon dioxide back into the atmosphere.
Other larger external factors determine an ecosystem’s climate, time, topography, and material at the earth’s surface — these factors are not influenced by the ecosystem itself; they simply exist. Rainfall and temperature determine the amount of water and energy available to a system. Climate determines what sort of biome an ecosystem is in — these factors make one region a desert, another one fertile land, and another one a lake.
Internal factors change how different species interact with each other. For example, if one species contracts a disease and dies off, it affects the whole system. These factors both control and are controlled by ecosystem interactions. In this way, there are different from external factors.
Ecosystems are often a part of a larger biome, which should not be confused with an ecosystem: biomes are large areas of land based broadly on climate type and the species present. They are not based on the interactions between living and nonliving parts of a system.
An ecosystem is defined as such because the species that interact form a network that depends on the environment. So a forest, such as the Amazon rainforest, can host many different ecosystems: a soil ecosystem, an understory ecosystem, a canopy, and a forest floor ecosystem. All the members of each system interact with one another and form a closed system.
Ecosystems are dynamic: they can change based on external or internal factors. The variation in climate can cause situations such as droughts, where all but the most resistant plants die. The animals and microorganisms that depend on these plants would also be affected. New species sometimes also arrive. For example, a new bird that eats a certain insect can come to an area. That insect will now be less abundant and affect the plants that it used to feed upon as well as the other animals that eat this plant. The animals and plants that live in an ecosystem are perfectly suited to these particular living conditions. Changes in external factors, like temperature, can change the plants grow and, therefore, the animals that eat the plants might adapt, move, or die in response.
The normal functioning of an ecosystem provides humans with an abundance of services that we depend upon or that can significantly improve our quality of life. For example, pollination is necessary for about 75% of our crops, trees provide us with timber, and the oceans provide us with fish. The list of ecosystem-provided services is very, very long and includes several more nuanced entries that we tend to take for granted, like clean air, a stable climate, and safe drinking water.
Human action is currently disrupting a large number of ecosystems. For example, by removing most of the fish from the ocean, the whole food chain and system are disrupted and can no longer function properly. The result is running out of certain types of seafood that we enjoy. Introducing invasive species also influences ecosystems because these invasive species outcompete several of the native species that are necessary for the system to work properly.
On a larger scale, humans are even capable of influencing external factors. By causing the earth to warm via increased carbon dioxide emissions, it influences which plants and animals can live where. It is true that new species often enter ecosystems and that climate can naturally fluctuate but the current changes are so frequent and sudden that the ecosystems cannot adapt to new equilibrium. We are also shooting ourselves in the foot because disrupting ecosystems could have disastrous effects on ourselves: no pollination and hence few crops, bad air quality, fewer fish, and contaminated water are just a few examples. Maintaining the balance of the ecosystem benefits us personally.
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