Lisa has taught at all levels from kindergarten to college and has a master's degree in human relations.
Balance in an Ecosystem
Imagine you purchase an aquarium and fill it with some sand, a few aquatic plants, and some small rocks. Add water and a couple of fish to the aquarium and voila! Your miniature ecosystem is complete.
An ecosystem consists of the living and non-living things that interact with one another in a particular location. In the example above, the fish and plants both live in the water, plants provide oxygen for the fish and rocks provide them with shelter, and the fish nibble at the plants and prevent overgrowth. All of the elements of the ecosystem you have created are in harmony. When this type of stability exists in an ecosystem, we call it a balanced ecosystem.
Unfortunately, ecosystems do not always remain in balance. Environmental changes can alter the stability of an ecosystem, creating unbalanced ecosystems. This may be helpful to an ecosystem in some instances, but it also can be destructive. Think of how the ecosystem in your aquarium benefits when you clean the water. Now imagine how your aquarium's ecosystem might suffer if all of the plants were to die.
Natural disturbances are one way an ecosystem can become unbalanced. As the name implies, natural disturbances have natural causes, such as weather, geological forces, or biological changes. Fires and floods are examples of natural disturbances that force change upon an ecosystem. Natural disturbances are also caused by diseases, severe storms, insects, volcanic activity, earthquakes, droughts, and long-term freezing.
Let's say you go on vacation for a week and leave your aquarium. While you are gone, a blizzard hits and your house loses power and heat for the week. Temperatures drop to near freezing inside your home for a number of days. Your aquarium is small, so the effect of the cold is similar to long-term freezing in a larger ecosystem. The water temperature falls below the temperature the fish needed to survive, and when you return home, all of the fish in the aquarium have died.
Natural disturbances can do a lot of damage to an ecosystem, even killing plants or animals, as in the aquarium example. But natural disturbances are nothing new, and the effects are usually temporary and the ecosystem will eventually recover. It may be the same after it recovers, or it may include new plants and animals that balance out the ecosystem as it adjusts to the new environmental conditions. It may be hard to imagine ecosystems recovering after some natural events. For example, if you've ever stood among charred trees and blackened ground after a forest fire, you know that fires and other natural disturbances can do a tremendous amount of damage.
However, in some cases, natural disturbances can be beneficial to an ecosystem. There are even some ecosystems that have adapted to become dependent on natural disturbances to maintain their balance. For example, longleaf pine forests depend on occasional fires to control undergrowth in the forest. Without a forest fire clearing the way for new seedlings to grow, the tiny new trees are unable to compete with the thick brush and die.
Not all changes to an ecosystem are caused by natural forces. Ecosystems are also affected by human disturbances, which are caused by people. Chemical pollution and urbanization are examples of human disturbances that force change upon an ecosystem. Other examples include deforestation, mining, and light or noise pollution.
Think of your aquarium again. When your five-year-old cousin came to visit, he really liked feeding the fish and watching them eat. Unfortunately, he kept dumping fish food in the aquarium over and over again. This caused the water to turn cloudy, and the fish had a hard time filtering the water through their gills to breathe. Luckily you were able to put clean water back into the aquarium as soon as your cousin left and the fish survived.
Just like your cousin's presence had an effect on your aquarium and put stress on the fish, human presence has had a significant effect on the world's ecosystems. As we use chemicals, remove trees, move water, and change the landscape to fit our needs, we affect ecosystems. We may introduce non-native species that disrupt an ecosystem or pollute the air and cause climate change. Most human impact is negative because it places undue pressure on ecosystems to adapt.
An ecosystem is made up of the living and non-living elements of a habitat that interact with one another. In a balanced ecosystem, all of the elements exist in a stable and harmonious state. This stability can be disrupted by natural disturbances and human disturbances. When a natural or human disturbance happens, it results in an unbalanced ecosystem.
A natural disturbance is simply a disturbance with a natural cause, such as a fire or flood. It could also be a natural disaster, such as an earthquake, volcanic eruption, or severe storm. It could even be caused by climate changes, insect swarms, or disease. Natural disturbances can be destructive, but the effects are usually temporary and can also bring beneficial changes to an ecosystem. A human disturbance is caused by people. Different types of pollution, urbanization, deforestation, and mining are all examples of human disturbances. Human disturbances can have a significant impact on an ecosystem. The effects of human disturbances are generally considered negative because undue pressure is placed on an ecosystem to adapt.
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