Chapters
In this article, we will discuss species and populations that can become extinct because of certain factors like climate change, competition, hunting by humans, and degradation and loss of habitats.
The species become extinct when they get diminished as a result of certain environmental forces. In simple words, extinction occurs when species die out or come to an end. Extinction is a natural biological process that has been occurring on planet earth since the beginning of life. The studies of fossils and ancient DNA have revealed that millions of species became extinct in the past.
Mass Extinction
Mass extinction events also took place in the past when a huge number of species became extinct at once. Mass extinction occurs when the rate of extinction is extremely high. There is a high probability that mass extinctions in the past occurred because of the major and sudden changes in the environment. Examples of such changes include the Ice Age and an asteroid hitting the planet earth.
Reasons of Extinction
Scientists are studying the recent rates of extinctions in current years. They believe that our planet is undergoing mass extinction because of certain environmental forces. They believe that due to human activity, several species are on the verge of extinction. Extinction may take place because of the following reasons:
- Climate change
- Competition
- Hunting by Humans
- Introduction of species
- Degradation and loss of habitats
Now, we will discuss all the above reasons for extinction one by one in detail.
Extinction due To Climate Change
Humans burn a tremendous amount of fossil fuels every year which has increased the levels of carbon dioxide in the atmosphere. The increased levels of carbon dioxide in the atmosphere have created a greenhouse effect.
How increased levels of carbon dioxide affect ecosystems?
The increased concentration of carbon dioxide in the air has many negative effects on the ecosystems around the globe. It leads to:
- The rise in the mean global temperature
- The rise in sea levels
- The rise in ocean temperatures and acidity
- Melting of ice caps
Due to these negative effects, the habitats of some species have changed so much that they are unable to survive in the new environmental conditions. For instance, polar bears are affected because of the rise in temperatures around the world. They are struggling because every year their habitat melts away. When the ice caps melt quickly, they must swim further to reach seal populations that they feed on.
Extinction due to Competition
The limited resources in an area give rise to competition between individuals. Examples of these resources include food, habitat, water, and reproductive mates. Individuals of the same or different species can compete with each other for the same resource.
How Competition affects populations?
Due to the competition between individuals, the size of the population decreases. For instance, millions of years ago, there exist several different species of dogs in North America. When many species of cats spread from Asia to North America, then there were increased levels of competition between the carnivores. Consequently, today only nine species of wild dogs have left in North America.
In the last century, the competition by humans has posed a serious threat to some species because humans have taken their resources such as water, food, and habitat.
Extinction due to the Introduction of species
Human colonization in new lands often leads to the exchange of plant and animal species between their home country and the new one. The species they introduce to the new land are non-native which can be quite problematic because they usually do not have natural competitors, predators, or pathogens. As a result, their population grows uncontrollably in the new land.
Competitors, pathogens, and predators are the natural population checks that help to keep the population under control. In the absence of these checks, non-native species increase in number and negatively affect native species through factors such as competition and diseases.
Example
The introduction of grey squirrels in the UK in 1876 led to a decrease in the population of red squirrels. Initially, when grey squirrels were introduced to the UK, their population grew quickly. Grey squirrels competed with the red squirrels for food. Besides this, they also carry and transmit a disease called squirrel pox which is life-threatening for red squirrels.
Extinction due to Hunting by Humans
To survive, humans have traditionally been hunting, killing, and eating wild animal species. Today, most of us consume meat that comes from domesticated livestock such as sheep, cattle, and chicken. Because of the evolution of livestock, humans feel no urge to kill and hunt wild animals. Although, some humans in under-developed countries still hunt wild animals to survive, however, their percentage is very low compared to the past.
In some areas, the hunting of wild animals is still common as some people do it for fun. Hunting becomes more fun for some people if the species is rare and more vulnerable. If several individuals within a species are hunted, then the population of that species becomes extremely small and eventually becomes extinct.
Extinction due to Degradation & Loss of Habitats
Degradation and loss of habitats are the major causes of species extinction. In recent years, the aggressive destruction of animal habitats by humans has posed serious threats to other species. Humans destroy their habitats through activities such as draining wetlands, cutting down trees and polluting the land, air, and water. These human activities are quite dangerous for other species because they are already adapted to survive within their specific habitat and certain environmental conditions.
In the absence of their habitat, organisms are unable to obtain the resources they need to survive. The reduction in a habitat will compel a species to:
- Look for other suitable habitats
- Compete with other species for the remaining habitat
Consequently, the habitat range becomes extremely small or non-existent for a species to survive.
Conclusion
All the above factors explain why the population of a specific species decreases and become extremely small. Smaller populations are more vulnerable to extinction because they have a lower fitness which increases their mortality rate and decreases their rate of reproduction.
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