Due to the tremendous increment in the human population at an unprecedented pace and urbanization, the forest area and wildlife species have been shrinking day by day through activities such as forest encroachment, wildfires, and unsustainable harvesting of forest products. 

Several causes have been identified intending to detect the cause of wildlife declination at an alarming rate as mentioned below in brief:

Table of Contents

1. Overexploitation

Logging traffic of Laos
Illegal logging at Laos | Photo from Eco-Business

It is inferred as the significant driver of species extinction. Due to illegal logging, the forest resources have been reduced severely, causing a substantial decrease in forest cover. 

Apart from that, overfishing has led the fish species nearly to extinction. The findings insisted that the population of Pacific Bluefin Tuna fish species fell by approximately 97.4 %, which is a bit scary to reveal.

Unsustainable harvesting and overexploitation undoubtedly introduce pressures in the species enjoying their natural surroundings. 

2. Species invasion

Invasive plant species of Australia
Invasive plant species of Australia | Photo by GeoNadir

The species’ nature can either adapt or invade the changing environment. Species invasion is inferred as the most crucial threat that has resulted in the declination of the wildlife species. 

Introducing the new animal species in an unfamiliar habitat may invade the local species, thereby halting the proper growth and physical development—one example of a Brown tree snake suits in this matter. 

Over the years, the introduction and invasion of the brown tree snake in Galapagos Island in Guam resulted in the loss of Guam’s twelve native bird species.

Likewise, another example is the introduction of a large predatory fish named the Nile perch into Lake Victoria. 

The Nile perch population increment around the 1980s in the lake posed extinction of the endemic Cichlid species of the lake with 200 to 400 in number

The endemic Cichlid species in Lake Victoria could not adapt to the Nile perch’s invasion, thus resulting in the catastrophic loss of the crucial species of the nature lap. 

Undoubtedly, adverse effects in the species richness and the species number with the biodiversity loss of an ecosystem and the landscape as a whole.

The invasive animal species invades others so that within a short time interval, it poses severe threats to the animals and their habitat. 

It entirely influences the entire forest, grassland, and the aquatic ecosystem at a glance.

3. Habitat loss and fragmentation

Due to habitat loss, several wildlife species are threatened in the current scenario. Approximately 32.2 % of the forest globally has vanished since the pre-industrial era.

Once the forest habitat of the wildlife is fragmented and lost, it can negatively influence reproductive success. 

It may result in stark differences in the genetic characteristic of an organism, thereby causing the irreversible loss of biodiversity. 

The terrestrial wildlife population has been declining due to the advanced setup of infrastructures such as roads. 

Dams and water diversions have drastically fragmented the habitat of aquatic species such as fishes and tortoises. 

4. Pollution

buriganga river pollution
Buriganga river pollution affecting aquatic life | Photo by Dhaka Tribune

The accelerated rate of pollution in the present context has affected wildlife species throughout the globe. 

Around half of every wildlife species has been affected by the severe pollution effects, which entails copper redhorse fish and gypsy cuckoo bumblebee.

To boot, due to the impact of light pollution, it can disrupt the migratory birds’ routes and habits. 

The induced sound pollution resulting from the shipping lanes undoubtedly drops out the communications channels between the marine species.

Due to the increase in pollution, numerous fish species have been limited in the aquatic graveyard.

5. Disease

The disease is also referred to as the fundamental cause of the species in a declining stage. It accounts for almost a 2 % loss in biodiversity

Despite the cause of diseases to fall the species, it does not contribute at a higher rate than the other fundamental reasons that have been visualized so far.

Due to the infections caused by bacteria, viruses, and fungi resulting from climate change, several wildlife species have been victims of diseases. It results in the declination of the species.

The pressuring examples entail the marine mammal’s morbillivirus caused outbreaks of the diseases in the coral reefs. 

Since the alarming rate of coral bleaching is boosting up, the conditions further add to the declination of the wildlife species. 

The expansion of the infectious diseases chytridiomycosis resulting in a pandemic in amphibians had too caused the decline of the wildlife species.

6. Climate change

Climate change and its changes in the last 50 years.
The description of climate change and its changes in the last 50 years | Illustration by GISS

Climate change acts as the most harmful cause creating severe impacts on the decline of wildlife species. There are several vital indicators revealing the intensity of climate alteration.

Since the Industrial Revolution’s establishment, wildlife declination and extinction have increased tremendously in the name of urbanization. 

IUCN illustrates that climate change fundamentally targets those wildlife species with smaller geographic ranges, particular habitats, and less mobile nature.

The snowmelt in the higher Himalayas, acidification of the ocean, coral bleaching resulting in 30-60 % of the coral reefs, rise in the sea level, and unusual patterns of temperature and the precipitation are the primary cause of the wildlife species in declination and extinction, a more in the post-industrial era.

The research depicted that around half of the threatened terrestrial mammals and a quarter of the endangered birds have been victims of climate change-induced effects. 

7. Illegal wildlife trade

The word ‘Illegal wildlife trade’ seems dangerous since it includes an extensive network at the international level. 

Due to the illegal wildlife trade of species such as lions, red panda, leopard, and deer, they are on the verge of extinction, posing significant threats to the entire ecosystem. 

There is a high demand for ivory throughout the world, particularly in the countries such as Nepal, the United States, China, Germany, and the African countries.

The endangered wildlife often seems to be the massive target of the poachers in the hope of achieving high economic value. 

Apart from this, the alteration in the number of species may directly hamper the food chain and the food web.

Concerning Facts

  • The decline of wildlife is on an average of two-thirds in less than half a century.
  • Approximately 68 % average declination of the vertebrate species populations between 1970 and 2016. 
  • Between 1994 and 2015, the illegal hunting of the eastern lowland gorilla in Kahuzi-Biega National Park of Congo covers approximately 87 % of the species’ decline.
  • The present extinction rate will be increased by around 1000 times higher than the rate in the natural background. 
  • 27 % of the species are threatened with extinction among 93,579 species being assessed, targeting more than one-fifth of the critically endangered species.


The accelerating rate of human activities such as pollution, habitat loss and fragmentation, invasion of the wildlife species, illegal wildlife trade, and many more have created devastating pressures on the wildlife. 

It looks pretty effective to conserve our wildlife species and prevent them from declination if we follow “Think globally, act locally,” as stressed by Scottish conservationist Patrick Geddes. 

Still, it has not been too late to act for wildlife species conservation if we are in hand to hand, adequately targeted-oriented plans and effective implementation of the committed programs.

(Last Updated on May 26, 2022 by Sadrish Dabadi)

Kalpana Ghimire holds a post-graduate degree in Environmental Science from Nepal. She possesses numerous research experiences working in water pollution, community forestry, environment conservation status, and wildlife ecology. She was an internee in the Department of Environment (EIA monitoring and auditing section) under the Government of Nepal. Kalpana Ghimire is an avid traveler, an enthusiastic wildlife researcher, and has a huge passion for working in the environment sector. She loves far traveling to the natural areas, conducting field wildlife research and reading the novels.