Introduction to Natural Ecosystems
Environmental degradation is a major issue of our time. A basic environmental building block is the ecosystem.
This article is intended to provide a resource for people who want to learn more about what ecosystems are and how they work. When I was working on a project on this same subject, I couldn't find any resources that offered a basic, thorough overview, so I decided to provide one myself!
Along the way, we'll look at:
- Natural vs. artificial ecosystems
- The different types of natural ecosystems
- How an ecosystem functions
- Human impacts
The Definition of "Ecosystem"
An ecosystem is a combination of two words: "ecological" and "system." Together, they describe the collection of biotic and abiotic (living and non-living) components and processes that comprise a defined subset of the biosphere. (The "biosphere" is the area of Earth that contains life, whether on the planet's surface or in the air.)
Natural vs. Artificial Ecosystems
- Natural ecosystems may be terrestrial (such as a desert, forest, or meadow) or aquatic (a pond, river, or lake). A natural ecosystem is a biological environment that is found in nature (e.g. a forest) rather than created or altered by man (a farm).
- Humans have modified some ecosystems for their own benefit. These are artificial ecosystems. They can be terrestrial (crop fields and gardens) or aquatic (aquariums, dams, and manmade ponds).
This article focuses on types of natural ecosystems, how they work, and what we can do to protect them.
Types of Natural Ecosystems
There are two main types of natural ecosystems, aquatic and terrestrial.
- In aquatic ecosystems, organisms interact with water. (The prefix "aqua" means water.)
- In terrestrial ecosystems, organisms interact with land. (The prefix "terra" means land.)
Aquatic ecosystems cover 71% of the earth's surface. There are three different varieties, defined by the kind of water in which the system's organisms interact.
- Freshwater: This type includes lakes, rivers, ponds, streams, and some wetlands, and makes up the smallest percent of the earth's aquatic ecosystems.
- Transitional communities: These are places where freshwater and saltwater come together, such as estuaries and some wetlands.
- Marine: More than 70% of the earth is covered by marine (also called saltwater) ecosystems. These include shorelines, coral reefs, and open ocean.
The four terrestrial ecosystems are classified by the type of land or terrestrial area in which organisms interact.
- Forest: These ecosystems feature dense tree populations, and include boreal and tropical rain forests.
- Desert: Deserts receive less than 25 cm of rainfall per year.
- Grassland: These ecosystems include tropical savannas, temperate prairies, and arctic tundra.
- Mountain: Mountain ecosystems include steep elevation changes between meadows, ravines, and peaks.
How Ecosystems Work
Energy and the Food Chain
Life is based on energy. On Earth, the sun is the primary source of energy. Plants turn sunlight into chemical energy through a process called photosynthesis.
Plants and trees are the energy producers. Herbivores (plant eaters) and carnivores (meat eaters) are energy consumers. They take in the chemical energy from sunlight through the food they eat. With that energy, they carry out all the processes of life.
The food chain illustrates this energy relationship.
When an insect eats a plant, the insect takes in some of the sun's energy. If a bird eats the insect, the energy is transferred again. When a mammal, like a wildcat, eats the bird, then the energy is transferred one more time. This is how energy flows through an ecosystem.
All organisms and ecosystems on Earth are linked to one another. They are said to be "interdependent."
The principles of ecological interdependency are:
- All species are dependent upon one another, either directly or indirectly.
- When one is removed, whether through extinction or for human use, other species are affected, however indirectly.
- The impact of one species' extinction can slowly cause the extinction of other species.
An example of these principles is the relationship between sea otters, kelp, and sea urchins. Each species depends on the others. Sea urchins eat kelp and sea otters eat sea urchins. Each of these species are harvested by humans, which can upset the balance among the three. When humans hunt sea otters, their populations decline. When the sea otters are killed or adapt by moving away, then sea urchins increase, potentially devouring entire stands of kelp. If humans harvest too many sea urchins, they can cause a decline in the sea otter populations that rely on those urchins. In response, the sea urchins can rebound in extreme numbers, denuding the kelp forest and discouraging sea otters from returning.
Without human efforts to conserve natural resources, as well as recycling and reusing those we have already harvested, some of those resources will be gone forever. If we do not take care of our planet's delicate balance of ecosystems, then that will be the end of us and our world.
Ecosystems require balance to thrive. When one element increases or decreases, the ecosystem must adapt to the change. For example, if a meadow or forest ecosystem receives less moisture than is normal, the fruit-bearing plants may not produce as much food for native animals. In turn, those animals will reproduce at a lower rate.
Humans have had a disproportionate impact on the earth's ecosystems. The fertilizers used in farming, for example, often run off into streams and lakes, causing more algae than usual to grow. The increased algae kills off plants and animals in the lake, throwing the lake's ecosystem out of balance.
Human behavior has introduced pollution into the earth's ecosystems through the air, water, and soil. Also, our use of natural resources, especially fossil fuels, is altering the environment in serious and alarming ways.