Which of the following is the best example of a way human lifestyles affect environmental systems?

A. Burning fossil fuels increases the amount of greenhouse gases in the atmosphere.

B. Using radioactive materials causes ground pollution when chlorofluorocarbons (CFCs) seep into the ground.

C. Deforestation causes water pollution by decreasing water vapor in nearby lakes and rivers.

D. Using aerosol sprays increases the amount of ozone (O3) in the atmosphere.

The correct answer is A. Burning fossil fuels increases the number of greenhouse gases in the atmosphere.

Diagram showing levels of greenhouse gases over time
Diagram showing increasing levels of greenhouse gases over time

Humans have had an enormous impact on the environment and on wildlife. This impact has for the most part been negative. One of the best examples of how humans have negatively affected environmental systems is through the burning of fossil fuels.

This process causes the release of several greenhouse gases into the atmosphere. The earth receives a certain amount of solar radiation from the sun, some of which is reflected back into space.

A greenhouse gas is a type of gas that absorbs a great deal of this reflected solar radiation. In fact, water vapor, carbon dioxide, nitrous oxides, and methane are the main greenhouse gases of concern.

The problem with substances absorbing too much radiation is that the temperature of the earth is affected. This means that a greenhouse effect is created in which radiation which should be escaping the atmosphere remains trapped causing global warming.

Global warming may have severe consequences for humans living in low-lying areas and may cause extreme climate events. Plants and animals may also be negatively impacted by climate change.

Greenhouse gases

These are the gases that when released into the atmosphere, function to trap solar radiation which has the result of affecting the temperature of the earth. The most common greenhouse gases caused by human activity are carbon dioxide, nitrous oxides, and methane.

In fact, the emission of carbon dioxide and methane is due mostly to the burning of fossil fuels in industry. Carbon monoxide is also released during incomplete combustion reactions, and this gas indirectly affects global warming by reacting with other substances in the atmosphere.

Various gases, including nitrous oxides and carbon monoxide, are also produced from the engines of motor vehicles on the roads. However, newer vehicles are designed to be cleaner and release lower amounts of emissions into the atmosphere. In addition, some governments have now enacted laws to make industry control emission levels.

Many gases are produced as a result of combustion reactions, which typically occur in motor vehicles and many industrial processes. Such greenhouse gases have increased over the years from the end of World War II when more fossil fuels started to be used.

Global warming

The concern with the burning of fossil fuels and the release of the gases is that it affects the climate. In fact, climate models based on emission rates of a variety of gases have predicted that global temperature will have increased by 1.4 to 5.8oC from the year 1990 to 2100. These climate models are based on a variety of emission scenarios.

It is important to understand that temperature does not rise equally in all areas each year, so the global average temperature is what is important. Temperature measurements by NASA have shown that temperature, on average, has increased by 0.20oC every ten years.

There is still some debate on how much of an impact humans have actually had on global warming since scientists have recorded periods of cold and warm temperatures throughout geological time.

Consequences of global warming

There are ramifications to changes in global temperatures, including the effect on precipitation. Warmer temperatures can be expected to increase evaporation rates.

This could result in more rainfall and severe weather events such as hurricanes occurring in some parts of the world, while other parts of the world may actually become drier.

Increasingly warm ocean waters and melting ice caps could lead to a rise in ocean level. This has consequences for people living in low-lying areas since these may become flooded in the future.

Plants and animals

Climate influences the distribution of biomes and affects plant and animal life. Many life cycle events of such organisms are triggered by a change in climate. This means that changes in climate over time are expected to influence the timing of life cycles.

Photoperiod, which is changing day length does also influence the timing of life cycles, but temperature also plays a role. Rainfall and temperature impact vegetation growth and the availability of insects.

Furthermore, the abundance of plants and insects then has an effect on animals further up the food chain that depends on these organisms for food.

Experiments have already demonstrated increased plant activity in bogs with higher temperatures. Furthermore, this study of bog plants showed an earlier spring development of plants but a slower response to autumn.

The result that was found was that the delayed response actually caused more plants to suffer tissue damage, which suggested that the plants could not adapt quickly to changes in climate.

There is also evidence that sockeye salmon in the ocean are adversely impacted by ocean temperature changes. The distribution of this fish species is limited by temperature. As result, any change to this thermal boundary will influence the range of the salmon population.

Furthermore, biologists predict that if ocean temperatures rise too much that the salmon population numbers will drop substantially. This will then have ramifications throughout the food webs in the ocean.

Other human impacts

Humans do have many other negative effects on environments due to land-use practices such as deforestation, fragmentation of natural habitats and overhunting or harvesting of animals.

In fact, deforestation increases soil erosion and destroys crucial animal habitat. This habitat loss can lead to the extinction of plant and animal species.

Pollution is a big concern and is not limited to air pollution. Radioactive and other waste products can severely impact the environment when they accumulate in soils and waters.

In the 1980s, aerosol sprays containing CFCs actually started destroying the ozone hole.  Laws were enacted in 1987, which have now made the use of these chemicals in sprays, largely illegal. This has helped somewhat to reduce the rate of ozone destruction.


  1. ME Mann (2018). Greenhouse gas. Retrieved from Encyclopedia Britannica.
  2. TJ Wallington, et al. (2009). Greenhouse gases and global warming. Environmental and ecological chemistry.
  3. NK Kondratiev (2018). Combustion. Retrieved from Encyclopedia Britannica.
  4. JA Nathanson (2018). Air pollution. Retrieved from Encyclopedia Britannica.
  5. AD Richardson, K Hufkens, T Milliman, DM Aubrech (2018). Ecosystem warming extends vegetation activity but heightens vulnerability to cold temperatures. Nature.


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