Lesson 2.04 Human Impact on Ecosystems

All organisms on Earth have a particular role that they play in the environment known as a niche. An organism's niche includes all aspects of its role in the environment, such as:

• what it eats,
• how it obtains its food,
• what it uses for shelter,
• how it obtains its natural resources,
• how often it reproduces, and
• how many offspring it has (i.e. the role that it plays in the ecosystem's food web).

While organisms can occupy the same niche, the actual physical place that an organism occupies is its habitat. Both an organisms's habitat and in turn its niche can be affected by the different relationships with an ecosystem.

As you have learned in previous units, there are natural fluctuations and changes to an organism's ecosystem. A population may increase or decrease based on the different relationships within an ecosystem, such as

• competition,
• predation,
• parasitism,
• disease,
• natural disasters, and
• human impact.

Most of the relationships in an ecosystem are natural and part of the way the Earth maintains a balance throughout the biosphere. This balance is often called homeostasis.

However, because of their superior intellect and problem solving skills, humans have developed technologies and solutions that have allowed them to manipulate the natural order of the environment for their benefit. As the world's human population grows, the effects that humans have on the planet/environment continue to increase and become more drastic. The natural checks and balances can become disrupted, which can cause harm to the environment.

A number of noticeable things happen in the environment as countries within the world continue to grow and develop.

• More energy is used to help maintain a higher standard of living.
• More land/habitat is destroyed to build places to live, grow crops, mine for precious metals and fossil fuels, and obtain building materials.
• More waste is created.
• More pollution is put into the air, water, and soil.

When the above happens, organisms within the environment are affected. They lose food sources, water sources, and habitat. This loss affects the population numbers because the amount of energy available is reduced and/or the amount of habitat is reduced. When habitats and niches are altered, numbers decrease and organisms can become

• threatened,
• endangered, or
• extinct.

Threatened species are those whose numbers are trending down and are at risk of becoming endangered.

Endangered species are those species whose numbers are so low that they face the possibility of extinction.

Extinct species no longer exist; they have been totally eradicated from the earth. Throughout history, there have been five mass extinctions. It is estimated that 99 percent of all life that has existed over Earth's history is extinct. Mass extinctions in the past have been caused by natural events, such as climate change, volcanic eruptions, and the earth being impacted by asteroids. Mass extinctions have allowed for new species to gain a foot hold and succeed on earth. It is predicted that the next mass extinction will be caused by an event or series of events caused by human impact.

The following human impacts on the environment have occurred because population numbers have grown and standards of living have increased.

CO₂ Emissions: One of the main sources to generate energy for human use is the burning of fossil fuels. When fossil fuels are burned, carbon dioxide is emitted into the atmosphere. This added carbon dixoide can cause changes to the environment, like global warming, and it can create environments in which organisms cannot live. See in the graphic below from Population Education how carbon dixoide emissions have increased since the early 20th century.

Dead Zones: People on average have increased their energy usage per person since the 1970s. The number of dead zoneslow oxygen areas in the oceans have increased over the last 50 plus years due to oxygen depletion because of human activities.

Read Smithsonian: Ocean Dead Zones Are Getting Worse Globally Due to Climate Change and NOAA: What is a dead zone? to learn more about dead zones.

Overhunting, overfishing, poaching, and consumption: The use of improper hunting and fishing practices impact that species. If the species is endangered, it can drive it to extinction. The percentage of live coral reefs in the Caribbean have decreased since the 1970s. The amount of land surface in the tropical rainforests have decreased in the last 50 years. Average meat and paper consumption per person have significantly increased in the last 50 plus years. Water and food shortages have increased. Study the graphics from Population Education that display how humans have impacted the different parts of the environment.

Invasive Species: Not only do humans negatively affect the Earth by using or destroying resources through consumption and pollution, but humans have also disrupted the environment through the introduction of non-native species or invasive species into ecosystems. Introducing invasive species changes the make-up of an ecosystem. The new species has to have resources, such as food, water, space, and shelter. Oftentimes, these non-native species do not have any natural predators so their populations grow unchecked. When this growth happens, the introduced species take up the niches and habitats of the native species.

An example of a non-native species in Alabama and much of the southeastern United States is kudzu. Kudzu was introduced into the United States during the 1800s. It was thought to be a potential good source of food for livestock. In the 1930s with the loss of soil due to erosion, it was often planted in areas susceptible to erosion to help prevent soil from washing away. Now as you drive along any rural road in Alabama, you can see the presence of kudzu. It has thrived and taken over. It chokes out natural plants

Read National Wildlife Federation: Invasive Species and University of Alabama: The Amazing Story of Kudzo to learn more about invasive species.

Because of the growing number of species that were becoming extinct or almost extinct, the United States government passed the Endangered Species Act of 1973 (ESA). This act protects threatened and endangered plants and animals and the habitats in which they live. According to the Environmental Protection Agency "The ESA requires federal agencies to ensure that any action they authorize, fund, or carry out, will not likely jeopardize the continued existence of any listed species, or destroy or adversely modify any crititcal habitat for those species."

There are over 1,200 species listed as either threatened or endangered in the United States according to the ESA. The National Oceanic and Atmospheric Administration (NOAA) manages the marine and anadromous fish speciesA species that is born in freshwater, spends most of its life in the sea, and returns to freshwater to spawn; an example is salmon.. The U.S. Fish & Wildlife Services (FWS) manages the terrestrial and freshwater species.

Go to FWS: Species Search to see threatened and endangered species in the United States. You can click on each state to see a list of species for that state. Also, go to FWS: Success Stories and click on different states to read highlighted stories about certain endangered species.

People are becoming more aware of the importance of protecting threatened and endangered plants, animals, and the habitats they occupy. The ESA and other local and federal laws have led the way. The National and State Park Services have been created to help protect species. Local and state governments and nonprofit organizations have helped establish areas known as wildlife sanctuaries in order to help protect species on the verge of being threatened or endangered.

During the environmental movement of the early 20th century, two views of protection emerged: preservation and conservation.

Preservationists set out to protect nature from human use. They seek to eliminate human impact all together. Their ideal protection plan is one in which does not involve any human consumption or use.

Conservationists seek for humans to properly use nature. They seek to regulate human use in order to best serve the environment.