Global Climate Change and Evolution

Polar ice melts may contribute to the extinction or evolution of polar bears.
Polar Bear on an ice floe in Norway. Getty/M G Therin Weise

It seems like every time a new story is created by the media about science, there needs to be some sort of controversial subject or debate included. The Theory of Evolution is no stranger to controversy, especially the idea that humans evolved over time from other species. Many religious groups and others do not believe in evolution because of this conflict with their creation stories.

Another controversial science topic often talked about by the news media is global climate change, or global warming.

Most people do not dispute that the average temperature of the Earth is increasing every year. However, the controversy comes in when there is an assertion that human actions are causing the process to speed up.

The majority of scientists believe both evolution and global climate change to be true. So how does one affect the other?

Global Climate Change

Before connecting the two controversial scientific subjects, it is first important to understand what both are individually. Global climate change, once called global warming, is based on the annual increase of the average global temperature. In short, the average temperature of all places on Earth increases every year. This increase in temperature seems to be causing many potential environmental issues including the melting of the polar ice caps, more extreme natural disasters like hurricanes and tornadoes, and larger areas are becoming affected by droughts.

Scientists have linked the increase in temperature to an overall increase in the amount of greenhouse gases in the air. Greenhouse gases, like carbon dioxide, are necessary to keep some heat trapped in our atmosphere. Without some greenhouse gases, it would be too cold for life to survive on Earth. However, too many greenhouse gases can have extreme effects on the life that is present.

Controversy

It would be pretty hard to dispute that the average global temperature for Earth is increasing. There are numbers that prove that. However, it is still a controversial subject because many people do not believe that humans are causing global climate change to speed up as some scientists are suggesting. Many opponents of the idea claim the Earth cyclically becomes hotter and colder over long periods of time, which is true. The Earth moves in and out of ice ages over somewhat regular intervals and has since before life and long before humans came into existence.

On the other hand, there is no doubt that current human lifestyles do add greenhouse gases into the air at a very high rate. Some greenhouse gases are expelled from factories into the atmosphere. Modern automobiles release many types of greenhouse gases, including carbon dioxide, that get trapped in our atmosphere. Also, many forests are disappearing because humans are cutting them down to create more living and agriculture space. This makes a large impact on the amount of carbon dioxide in the air because trees and other plants can use carbon dioxide and produce more oxygen through the process of photosynthesis. Unfortunately, if these large, mature trees are cut down, the carbon dioxide builds up and traps more heat.

Global Climate Change Affects Evolution

Since evolution is most simply defined as the change in species over time, how can global warming change a species? Evolution is driven through the process of natural selection. As Charles Darwin first explained, natural selection is when favorable adaptations for a given environment are chosen over the less favorable adaptations. In other words, individuals within a population that have traits that are better suited to whatever their immediate environment is will live long enough to reproduce and pass down those favorable traits and adaptations to their offspring. Eventually, the individuals that have less favorable traits for that environment will either have to move to a new, more suitable environment, or they will die out and those traits will no longer be available in the gene pool for new generations of offspring.

Ideally, this would create the strongest species possible to live long and prosperous lives in any environment.

Going by this definition, natural selection is dependent upon the environment. As the environment changes, the ideal traits and favorable adaptations for that area will also change. This could mean that adaptations in a population of a species that were once the best are now becoming much less favorable. This means the species will have to adapt and perhaps even undergo speciation to create a stronger set of individuals to survive. If the species cannot adapt quickly enough, they will become extinct.

For example, polar bears are currently on the endangered species list due to global climate change. Polar bears live in areas where there is very thick ice in the northern polar regions of Earth. They have very thick coats of fur and layers upon layers of fat to keep warm. They rely on fish that live under the ice as a primary food source and have become skilled ice fishermen in order to survive. Unfortunately, with the melting polar ice caps, the polar bears are finding their once favorable adaptations to be obsolete and they are not adapting quickly enough. The temperatures are increasing in those areas which make the extra fur and fat on the polar bears more of a problem than a favorable adaptation. Also, the thick ice that was once there to walk on is too thin to hold the weight of the polar bears any longer. Therefore, swimming has become a very necessary skill for polar bears to have.

If the current increase in temperature keeps up or accelerates, there will be no more polar bears. Those who have the genes to be great swimmers will live a bit longer than those who do not possess that gene, but, eventually, all will most likely disappear since evolution takes many generations and there just is not enough time.

There are many other species all over the Earth that are in the same sort of predicaments as the polar bears. Plants are having to adapt to differing amounts of rainfall than what is usual in their areas, other animals need to adjust to changing temperatures, and still others have to deal with their habitats disappearing or changing due to human interference.

There is no doubt that global climate change is causing problems and increasing the need for a quicker pace of evolution in order to avoid mass extinctions all over the world.