Ecosystems | Global Issues Tours

Learn more about Ecosystems
How to Help
Additional Resources

What are ecosystems, anyway?
Who is most affected?
Where are the consequences felt?
Why does harm to ecosystems continue?
Why are ecosystems important?
Citations

What are ecosystems, anyway?

An ecosystem is a dynamic complex of plant, animal and micro-organism communities and their non-living environment interacting as a functional unit.¹ Examples include a rainforest, a prairie, and coral reef. Ecosystems serve a variety of important functions in nature, from absorbing pollution to supplying food to conserving genetic resources.²

There are three primary types of ecosystems: marine, terrestrial, and freshwater.

An example of a marine ecosystem being studied by a scientist.

A terrestrial ecosystem in South Africa.

A freshwater ecosystem in France.

To learn more about ecosystems watch The Nature of Ecosystems, below.

Who is most affected?

We all make lifestyle choices that affect ecosystems, from our diet to our clothing to our housing. For example, as countries grow wealthier they demand a diversified diet that includes meat and dairy, which take more land to support than a traditional diet of grains. China’s consumption of meat has doubled in the last 20 years and is projected to double again by 2030.³ Because of our consumption patterns, we need more and more land, which is an expendable commodity.

The people living in three regions of the world will be most impacted by degradation of ecosystems: Africa, Latin America, and the Caribbean. In South Africa, for example, 9.5% of total terrestrial ecosystems have been destroyed or in danger of being destroyed.⁴ In Latin America, the Amazon rainforest is being deforested at a rate that will lead to 55% of the rainforest gone by 2030.⁵ In the Caribbean, coral reefs have declined from 50% cover in 1977 to 10-15% cover in 2001.⁶

Where are the consequences felt?

Here are interactive maps of marine, terrestrial, and freshwater ecosystems.

Fertilizer’s effects
For each kind of ecosystem, there are particular challenges that pose a risk. The use of fertilizers to boost crop yields has affected all three types of ecosystems. Fertilizers add excessive amounts of nutrients to the land, which then become present in water runoff into freshwater and marine ecosystems. Once introduced into the aquatic ecosystems, nutrients such as nitrogen and phosphorus cause the rapid growth of algae. When the algae decompose, the oxygen level in the water decreases, leading to the death of fish and other organisms.⁷

Overfishing’s effects
In marine ecosystems, overfishing due to improved technology has left the ocean ecosystems without the time to replenish the supply of fish. Half of the world’s wild marine fish stocks in the North Atlantic and in West Africa are fully exploited and therefore cannot provide any more fish than currently available.⁸

Coral reefs, home to over a million fish and other animals and plant species⁹, are another part of marine ecosystems that are being threatened. Corals are tiny animals that have a hard calcium carbonate skeleton, which is a home to zooxanthellae. The plant-like algae live inside the coral polyps and perform photosynthesis, producing food which is shared with the coral. In exchange the coral provides the algae with protection and access to light, which is necessary for photosynthesis. The zooxanthellae also lend their color to their coral.¹⁰ Increased sea temperatures, associated with climate change, have caused zooxanthellae to die off.¹¹ As a result, the white of the coral skeletons show through, a process called “coral bleaching”. The corals are still alive after bleaching but begin to starve. Most corals struggle to survive without their zooxanthellae.

A bleached coral in a reef in the Maldives, islands off the coast of India.

A triggerfish in a healthy reef in the Maldives.

Degraded land
In terrestrial ecosystems, deforestation and degradation have affected 8.5% of the world’s forest, half of which are in South America.¹² A major reason that forests and grasslands are being degraded is to create and maintain cropland. Agriculture has displaced one-third of temperate and tropical forests and one-quarter of natural grasslands.¹³

Deforestation in the Amazon rainforest. Intact forest is deep green, while cleared areas are tan (bare ground) or light green (crops, pasture, or occasionally, second-growth forest).

Damage to freshwater ecosystems
In freshwater ecosystems, the introduction of invasive species, high levels of pollution, and man-made changes like dams and irrigation have caused damage. From 1961 to 1999, the area of land under irrigation nearly doubled; the use of nitrogenous and phosphate fertilizers increased by 638% and 203% and the production of pesticides increased by 854%.¹⁴ Irrigation, fertilizers, and pesticides are ways to maximize agricultural production, which help to feed the world’s population and create biofuels. One consequence of using chemical fertilizers and pesticides is the mutation of freshwater species, like frogs. Examples of frog mutations are on this BBC website.

Why does harm to ecosystems continue?

As the world population has grown to almost 6.8 billion people in early 2010¹⁵, there is growing pressure on ecosystems to provide food, fuel, and medicines. Man-made features like dams have become more common as the need for drinking water increases. Forests and grasslands have been cultivated for use in agriculture, which disrupts the natural cycles that occur in those environments.

Why are ecosystems important?

Ecosystems provide services to the environment through four cycles—the water cycle, the carbon cycle, the nitrogen cycle, and the phosphorus cycle.¹⁶

Natural disasters happen more frequently and with greater severity as ecosystems are disrupted or destroyed. Ecosystems provide a buffer from the effects of climate change and from extreme weather events, with an estimated value of over $4 billion per year¹⁷: