Environmental Issues and Human Impact

The Earth is so large, how could one species have an impact upon it!?

As of 2014, humans have grown exponentially past the 7 billion mark. We humans share planet resources with other living things. We all depend upon these shared ecological resources for our survival.   It is important to understand our ecological impact so that we may manage the effect we have on the planet we rely on.

Renewable and Nonrenewable Resources

Ecological resources can be divided into two groups:

  1. Renewable resources – can be recycled or replaced naturally; Examples: plants, animals, crops, soil, water (if carefully managed) and wind, solar, geothermal power
  2. Nonrenewable resources – cannot be recycled or replaced as fast as we are using it; Examples: fossil fuels, nuclear power, metals such as gold, silver, copper

Look at the picture below that shows how much of each renewable resource is available to us, compared to the current global consumption. Do we use a large amount of the renewable resources available to us?


Total solar (left), wind, hydropower and geothermal energy resources compared to global energy consumption (lower right). There is far more renewable energy available than is being used.

Ecologists have used an economic idea first put forth by Garrett Hardin in 1968 called The Tragedy of the Commons to explain how resources can be misused. With this idea, individuals look out independently for their own interests, but forget about the interests of the whole group. This can result in the reduction of a valuable resource.

An example Hardin referred to in his paper involved a group of cattle herders sharing grazing rights on a common parcel of land. It was in each herder’s self interest to put all of his cows on the common land even though the quality of the land was depleted for all of the farmers through overgrazing. The farmer got an individual benefit while the group shared the burden of the consequences. If each farmer makes this same choice, the common land will be depleted or destroyed to the detriment of all. A more modern example of this problem is overfishing in the world’s oceans.

The Greenhouse Effect

The Earth is naturally warmed by a phenomenon called the Greenhouse Effect. In this process, solar energy hits the Earth and half of it is trapped in our lower atmosphere by greenhouse gases. Carbon dioxide, methane, ozone and water vapor are all greenhouse gases. We need the greenhouse effect to warm the Earth, especially at night.

When fossil fuels are burned to generate electricity or to run vehicles, more carbon dioxide is added to the atmosphere and may increase the greenhouse effect, resulting in global warming. Global Warming is the idea that a temperature rise caused by combination of different greenhouse gases such as methane and carbon dioxide will continue until ice packs melt and temperatures rise, causing a cascade of other ecological disturbances.


Pollution is the introduction of harmful substances into the environment. Pollution can take many forms:

  • air pollution
  • littering
  • soil contamination
  • water pollution

Pollutants can be biodegradable (wastes broken down naturally by bacteria or other decomposers) or non-biodegradable (takes 100’s to 1000’s of years to break down).

Pollution doesn’t just make the environment unpleasant to look at; it harms organisms and their relationships in the ecosystem. Humans are not immune to the effects, as shown in the diagram below. Be sure you have awareness of how each type of pollutant affects our health.


Eutrophication is the result of specific type of pollution. It occurs when fertilizer (or other chemical) runoff enters bodies of water and causes a population boom in the algae. This algal bloom, as it is called, results in an unhealthy body of water because the excess algae consume a large amount of oxygen during photosynthesis. Organisms living the body of water are left without enough oxygen to breathe. Eutrophication can also happen naturally in older standing bodies of water.


Acid Rain

Acid rain is a by-product of pollution. It occurs when water mixes with carbon dioxide to form carbonic acid, or when water mixes with nitrous oxide compounds to make nitric acid. When this mixture is deposited on the Earth in the form of precipitation (snow, sleet, rain) or particles, it may damage plants, impact fish populations and/or contaminate water.

View the short Acid Rain Interactive from EcoKids in the sidebar to see how acid rain affects a lake as the acidity increases.  Be ready: This resource opens with the sound of loud thunder! 

Biological Magnification

Biomagnification, is the increase in concentration (bioaccumulation) of a chemical in living tissues of organisms as trophic levels increase. The chemical is present in greater quantities at higher levels of the food chain, and is slow to be metabolized or degraded by the body. It is originally ingested by air, food or water.

Chemicals known to bioaccumulate include mercury, DDT, and PCBs. DDT is a chemical pesticide banned in the 1970s that demonstrated biomagnification; widespread use of DDT in agriculture and other fields contributed to the selection of DDT resistant mosquito populations.

Watch the short video clip below (from LOKE Films and AMAP 2002 Assessment) for a look at how the biomagnification of Mercury and PCBs have affected Arctic wildlife. Title: go to end of inline object

Pesticide Overuse

pesticide is a chemical that is applied to kill a targeted pest. Often pesticides can have dangerous effects on other organisms in the ecosystem. The pesticides can bioaccumulate in tissues, causing health issues, they may kill other organisms that were not a target, contaminate water through runoff, and with repeated use, cause pesticide resistance. Pesticide resistance means that the pesticide is no longer effective on the population of pests.

Integrated Pest Management (IPM) is an alternative approach to reducing pests that considers all possible pest control techniques to minimize environmental impact and its effect upon human health. It initially considers the use of safer, more natural pest deterrents before the use of chemical pesticides.

Ozone Depletion

The ozone layer is a collection of ozone molecules high in stratosphere. Ozone’s chemical formula is O3 and is made when ultraviolet light breaks apart oxygen gas (O2) into particles that reform as O3.

The ozone layer protects Earth from UV radiation, which contributes to sunburn and skin cancer. Watch the short video clip below (from Teacher’s Domain/Think TV) to gain a better understanding of Ozone and how it protects us from the sun’s damaging UV rays.

Breakdown of ozone is caused by manmade chemicals typically used as propellants (aerosol sprays) or coolants (air conditioners) called CFC’s (chlorofluorocarbons). In 1987 the Montreal Protocol was an international agreement to reduce the production of ozone depleting chemicals; so far this agreement has resulted in the gradual increase in ozone, though it is taking time to recover.


How many animals have gone extinct on our own continent? The answer is both unsettling and surprising. Visit the website in the sidebar for a listing of North American extinct animals, paying special attention to recent extinctions.


The Bald Eagle was removed from the Endangered/Threatened Species list in 2007.

How do we label organisms that are on their way to extinction?

  • Threatened – when population declines rapidly
  • Endangered – when numbers are so low that extinction is possible in near future
  • Extinction – disappearance of species

Causes of endangerment include:

  • habitat destruction
  • overuse of species for human benefit
  • disease or predation
  • other human factors

Why should humans be concerned about endangered species or species extinction when it is a normal process that has occurred over time? This is a valid question, but extinctions today are occurring at a rate that exceeds the rate of newly developed species when compared to other historical periods. Losing one or two species may have few environmental effects (some of the time), but if we lose enough links in our ecological chain, we may start to see a cascade of effects that threaten our own way of life. Once a species is lost, so is its contribution as food, diversity, or medicine.

The Endangered Species Act (ESA) was enacted in 1973 to protect critically impacted species from extinction and to remove threats to their survival. It is overseen by NOAA (National Oceanic and Atmospheric Association) and FWS (Fish and Wildlife Services). Since September 2012, over 25 species have been recovered due to efforts from the ESA.

Invasive or Introduced Species

kudzuAn invasive, or introduced species is a plant or animal species that is transferred to a new environment outside of its natural habitat. Because these are non-native they are often called “alien species.” They are generally a concern because they can cause considerable environmental, ecological and/or economic damage.

How do they get to their new location? Some hitch a ride on human transportation, some are accidentally transferred by humans, and others are brought intentionally to serve a purpose, such as decreasing the numbers of another population. Once in their new location, these alien species tend to outcompete native species for resources because they have some common traits that make them superior competitors, such as

  1. fast growth and reproduction
  2. tolerance of a wide range of conditions

Kudzu is an example of an invasive vine native to Asia and the pacific islands that has taken over many areas throughout the eastern U.S. It rapidly spreads over native vegetation, shading it out and killing it.