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3 Causes of Wildlife Depletion

I am a writer interested in environmental issues and the causes of disruption to wildlife populations around the world.

The number of wildlife populations lost over the past few decades begs the question, why?

The number of wildlife populations lost over the past few decades begs the question, why?

Shocking Losses to Wildlife Populations

A study by the World Wildlife Foundation (WWF), published in the fall of 2020, reported a shocking decline in wildlife populations over the last 50 years. The report concluded that between 1970 and 2016 populations of mammals, fish, reptiles, birds, and amphibians declined an average of 68%. The number of animals, birds, and reptiles lost over this period of time is almost incalculable. It's disheartening and angering to think about.

Major Factors in Wildlife Depletion

In this article, we will look into three major factors that are responsible for the decline or extermination of wildlife. These three major reasons are:

  1. Persecution by humans
  2. Loss of natural habitats
  3. Pollution

“No matter how few possessions you own or how little money you have, loving wildlife and nature will make you rich beyond measure.”

— Paul Oxton, Wild Heart Wildlife Foundation Founder and CEO

Oftentimes, the end result of hunting deer results in their heads and antlers being preserved and displayed as "trophies."

Oftentimes, the end result of hunting deer results in their heads and antlers being preserved and displayed as "trophies."

1. Persecution by Humans

When I say persecution by humans, I mean the specific targeting of animals by mankind, often referring to instances where their demise is perpetuated for fun and not out of the necessity for the survival of either species.

Main Forms of Human Persecution

  1. Hunting and shooting of wild animals for fun and amusement (or as "trophies"). It is reported that there are an average of 125 thousand animals killed and imported to the United States as trophies every year. Trophy hunting generates some 20 billion dollars a year, putting the act in line with the arms trade and sex trafficking.
  2. Illegal (or legal) hunting of animals for food (and, in turn, generating revenue from the cost of their delicious meat).
  3. Illegal killing or poaching for skin, fur, tusks, oil, plumage, decoration (as in taxidermy), etc.
  4. Killings by farmers or herdsmen living in the near vicinity of a jungle with predatory animals (think tigers, lions, jackals, wolves) who are unjustly accused of killing their domesticated animals or livestock.
  5. Trapping of animals to keep them as pets. There are domesticated species (like dogs and house cats) that do well with humans, while animals like exotic snakes and otters should be left in their natural environments. It is reported that there are some five thousand tigers being kept as pets in the United States, whereas there are only about three thousand wild tigers remaining around the world. It is really difficult for humans to provide tigers with the environments they need to really live as healthy a life as they would in the wild.
  6. Animals such as monkeys and rabbits that are trapped and then sold for the purpose of medicinal experiments.
  7. In many countries, animals such as monkeys, bears, and parrots are caught alive, domesticated, and trained for public shows in the streets or in big animal circuses. Again, some animals do well in the presence of humans (think dog shows), but humans cannot provide other more exotic animals with the correct conditions to support their livelihood.
Animals like koalas have suffered natural habitat loss due to a variety of factors such as deforestation, industrialization, and natural disasters. With the loss of habitats, their population's rate of survival drops off significantly.

Animals like koalas have suffered natural habitat loss due to a variety of factors such as deforestation, industrialization, and natural disasters. With the loss of habitats, their population's rate of survival drops off significantly.

2. Loss of Habitats

Another of the primary causes for the decline of wildlife is the degradation or complete loss of natural habitats. Like humans and house pets, wild animals need access to specific foods, shelter, clean water, etc. within a territory. If they are denied this stability, population numbers will gradually diminish. Today, somewhat ironically, most natural habitats that wild animals (and plants) need to survive are being destroyed by humankind's own activity.


Forests are being ruthlessly destroyed today all over the world for agricultural needs, river valley projects, industrial purposes, and roads, railways, dams, and building construction. The United Nations Food and Agriculture Organization estimates that every year some 17 million acres of forests are destroyed.

In fact, in just the last two decades, Afghanistan has lost some 70% of its forests. Another example is the Amazon rainforest. Under the current President of Brazil, Jair Bolsonarol, deforestation has soared 92%, according to satellite imaging and later reported by Time. As the forest is destroyed, the roughly three million species living in the Amazon face increasing threats to their livelihood.

Deforestation results in the fragmentation of natural habitats and reduces the area in which animals are able to move freely. The destruction of wild plants in forests for fuel, timber, fodder, and other uses also works to deprive animals of both shelter and their most palatable food supplies.


Overgrazing is another serious hazard afflicting our pastures, forests, and mountains. This refers to plants being overexposed to intense grazing by native or non-native animals without adequate recovery time. Overgrazing can also lead to erosion and the spread of invasive species. The areas may be even more subject to climate change since the native plants are no longer present to protect the earth.

The overexploitation of range lands by livestock grazing has resulted in more and more denuded hills and valleys, thus snatching away food and shelter from wild herbivores. When non-native species and plants are brought into an area, it makes it harder for native species to survive. This can happen anywhere in the world, and there has been documented evidence of overgrazing in countries all across the world.


Wetlands that are drained for cultivation or for the building of roads can disrupt native species. Wetlands are vegetated with various macrophytes, shrubs, and emergent marsh plants and are the prime habitats for waterfowl and semiaquatic vertebrates. They serve as an excellent refuge for a number of migratory birds that feed and breed there.

When those landscapes are disrupted or destroyed, the animals are left either having to quickly adapt or find new refuge, neither of which is realistic.

“Humanity can no longer stand by in silence while our wildlife are being used, abused and exploited. It is time we all stand together, to be the voice of the voiceless before it's too late. Extinction means forever.”

— Paul Oxton, Wild Heart Wildlife Foundation Founder and CEO

Pollution can be a byproduct of humans or a result of natural disasters.

Pollution can be a byproduct of humans or a result of natural disasters.

3. Pollution

National Geographic defines pollution as the following:

"Pollution is the introduction of harmful materials into the environment. These harmful materials are called pollutants. Pollutants can be natural, such as volcanic ash. They can also be created by human activity, such as trash or runoff produced by factories. Pollutants damage the quality of air, water, and land."

Pollution of various kinds has adversely affected wild animals. Here are some of the kinds of pollution.

DDT and Insecticides

There has been considerable damage to bird populations from DDT and other insecticide sprayings, especially when heavily concentrated applications have been used. Bird populations—especially birds of prey—have been significantly reduced through DDT poisoning. Research has shown that birds, due to direct or indirect intake of insecticides, produce eggs with fragile shells which then easily break when the mother sits on them for incubation.

Several decades ago, Charles Wurster, equipped with a Ph.D. in organic chemistry from Stanford, began studying the effect these chemicals had on birds. He and a group of colleagues collected bird carcasses from areas where DDT was used and conducted studies on the bodies. They concluded that even the adult birds lost control of their nerves and muscles after coming into contact with the chemicals. That was in addition to the effects the chemical had on the eggs yet to hatch.

After years of environmental organizations raising the alarm on the effects of DDT, it was not banned in the United States until 1972 after the Environmental Protection Agency worked to get it from being used further. In the years since, many bird populations, including the United States national symbol, the bald eagle, have seen their population numbers rebound considerably.

Though it cannot be used in the United States, it is still legal to manufacture and export. Countries like India use it for agriculture and African countries like Ethiopia, South Africa, and Uganda use it to help control malaria.

Spillage and Waste

Millions of oceanic birds are killed every year all over the world by spillage from oil tankers in the sea. Today, our rivers estuaries and shallow offshore areas have become waste bins for millions of tons of waste products from human activity. Our aquatic resources are becoming increasingly polluted by industrial waste, domestic sewage, and oil spillage. Due to water pollution, the biota has been seriously affected. Stocks of fish have declined and animals like oysters and mussels have become less fit for human consumption.

One of the more recent and extremely devastating oil spills was Deepwater Horizon in 2010 into the Gulf of Mexico. The Center for Biological Diversity estimated that some 82 thousand birds, six thousand sea turtles, 26 thousand marine mammals, and an incalculable number of fish were killed. In just the Deepwater Horizon catastrophe alone some 205.8 million gallons of oil and 225,000 tons of methane spilled into the ocean. Only around 25% was recovered.

Noise Pollution

Noise pollution by vehicles like heavy trucks, buses, rails, and airplanes has adversely affected wildlife. There are several reasons why noise could affect an animal's livelihood, many of which may not seem obvious at first thought. Many animals use highly attuned sounds to communicate for reasons like calling out danger or as a way of mating. These can all be disrupted by human-generated noise.

Other animals like dolphins and bats use sounds to help navigate and when traffic or sonar noises dominate, it can throw the animals off. Other animals of prey like cats and owls need quiet environments to capture their food. Though changes in the levels of noise may seem minuscule to humans, this pollution can disrupt these animals greatly.

Final Thoughts

As you can see, humans, their activity, and the ensuing pollution generated is devastating to wildlife populations around the world. There are countless organizations and activists working to mitigate the effects humans have on animals, but with continued development, climate change, and a general stubbornness from humans overall, more and more species will continue to suffer. Others will likely face extinction soon.


This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2021 Aqsa Shahid


Aqsa Shahid (author) from Gujranwala on January 29, 2021:


Aqsa Shahid (author) from Gujranwala on January 29, 2021:


Aqsa Shahid (author) from Gujranwala on January 28, 2021:

great work