12 Reasons Why Species Become Endangered

Species around the world are disappearing at an alarming rate. In fact, scientists estimate that human impact has accelerated extinction rates to as much as 10,000 times the natural rate. From deforestation and climate change to pollution and illegal hunting, a variety of factors have left nearly 50% of the planet’s species at risk of extinction in the near future.

But what does it really mean when a species is “endangered?” Put simply, it means that without immediate intervention, these species may be lost forever. The IUCN Red List, a leading global resource on endangered species, tracks these declines and categorizes species based on specific risk criteria. Understanding why species become endangered helps us recognize the human activities that need to change to protect biodiversity.

The United States Endangered Species Act sums up the problem succinctly: The Congress finds and declares that (1) various species of fish, wildlife, and plants in the United States have been rendered extinct as a consequence of economic growth and development untempered by adequate concern and conservation [and] (2) other species of fish, wildlife, and plants have been so depleted in numbers that they are in danger of or threatened with extinction.

In this article, we will explore the top reasons why species become endangered. By understanding these causes, we can better appreciate the urgent need to protect the planet’s biodiversity.

What Causes Animals to Become Endangered?

Causes of species endangerment are many, but conservation biologists recognize that multiple forces drawn along with human activity reinforce one another to cause a species to diminish. 

The general consensus is that it is the P for people that is the primary cause of the dramatic declines in species worldwide. The bottom line is that we have too many people consuming too much of the land and sea and the earth’s resources.

#1 Overhunting or overharvesting

This has been the fate of most large animals, slow animals and tasty animals when humans have migrated to a previously uninhabited area. 

History abounds with stories of animals going extinct because of hunting and the consequent deaths of their predators if not by direct hunting as well, then by starvation because they no longer have a food source.

And a long history of wildlife depletion it is… There are many historical accounts about how humans have over hunted and over harvested species, leading to their endangerment, and often, extinction. One extinct species, the Passenger Pigeon, is a classic example of how humans over hunted a species, leading to the extinction of the entire species.

It is the cause of some high profile near extinctions today, like elephants for their ivory tusks and rhinos for their horn. The horn is sold at exorbitant prices as cures from everything from hangovers to cancer.

The black rhino population was at 65,000 in 1970, but then an odd phenomenon occurred. The rise of oil prices due to the OPEC oil embargo made a lot of theretofore impoverished Yemenis very wealthy. 

Ceremonial daggers are bestowed upon young Yemeni males as a rite of passage and the most prized ones were made of black rhino horn, wildly driving the price up and the population of black rhinos down. 

By 1997, when Yemen at last became a party to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), only 2,400 black rhinos remained, leaving the species on the brink of extinction [5]. 

The most poached animals in the world today are the small, shy pangolins. 100,000 are poached each year for their meat, considered a delicacy on Vietnam and China and their scales, believed to have healing powers [7].

Plant species can also be overharvested, leading to their endangerment. For example, the Goldenseal plant is a very popular medicinal plant in the United States that has now become threatened due to overharvesting in the wild.

#2 Habitat loss

As human activities expand, natural habitats are transformed or destroyed, putting countless species at risk. For example, the Amazon rainforest, home to 10% of the world’s known species, has faced extensive deforestation to clear land for agriculture, cattle ranching, and logging. The impact is devastating: species like jaguars, sloths, and macaws are losing their natural homes and food sources. The loss of habitat makes it increasingly difficult for them to survive.

In Southeast Asia, the rapid spread of palm oil plantations has severely impacted species such as the orangutan. As rainforests are cleared for these plantations, orangutans lose both their habitat and access to essential resources. We have already captured starved orangutans in distress on videos. Without intervention, both the Bornean and Sumatran orangutans currently face a high risk of extinction.

In the wetlands of the Everglades in Florida, human development and water diversion projects have altered the natural water flow. This has affected species like the American crocodile and the wood stork, both of which rely on specific water levels to hunt, breed, and survive. As the Everglades continue to shrink and fragment, the survival of these species becomes even more uncertain.

Mountaintop removal mining in the Appalachian Mountains has had severe effects on local ecosystems as well. As mountains are stripped of vegetation and soil, species such as the Eastern hellbender salamander, which depends on clean, flowing streams, are left vulnerable. Pollution and sediment from mining destroy their habitats.

Urban expansion also fragments habitats and isolates species. In the grasslands of California, for instance, the San Joaquin kit fox is endangered due to habitat fragmentation from urban sprawl. Once able to roam freely, these foxes now navigate a patchwork of small, isolated grasslands, which reduces their ability to find food, shelter, and mates.

Across these examples, habitat loss forces species to adapt to new environments, which is unfortunately often unsuccessful. When animals and plants lose their primary habitats, they face increased competition, reduced access to resources, and higher mortality rates.

#3 Highly specialized species

Rarity has its own problems. Highly specialized species that have very specific habitat requirements do not fare well when faced with a changing environment.

A small or very local population only has problems due to lack of suitable mates, and inbreeding presents another set of problems. The higher the level of inbreeding the double the dose of defective genes are passed on, generally leading to sterility and early death.

Too, a small population is especially vulnerable to the vagaries of Mother Nature. A single strong storm, flood, wildfire or drought can be a death knell to a species.

While some species have become well adapted to human presence (e.g. the Norway Rat), some species are so specialized that changes in their environment may threaten their very survival.

The red panda is a prime example. Native to the Eastern Himalayas and China, red pandas rely exclusively on bamboo forests for food and shelter. As these forests shrink due to logging, agriculture, and climate change, red pandas face dwindling food supplies and reduced habitat. Without their specific bamboo diet, they cannot adapt or find alternative food sources.

Another example is the koala. This iconic animal relies almost entirely on eucalyptus trees in Australian forests. Koalas not only feed on eucalyptus leaves but also live within these forests, which are increasingly threatened by wildfires, deforestation, and urban sprawl. When wildfires swept across Australia at the end of 2019, it devastated koala populations, wiping out vast areas of eucalyptus forests and leaving koalas with little food or shelter. Their strict dietary needs make it difficult for them to relocate or adapt.

In North America, the Kirtland’s warbler is a rare bird species that nests only in young jack pine forests, which require fire to regenerate. Human fire suppression efforts have hindered the growth of these specific forests, leaving the warbler with fewer nesting sites. Conservationists have since intervened to manage and promote jack pine growth through controlled burns, but the species remains vulnerable due to its limited habitat preferences.

Highly specialized species are also at risk due to inbreeding. Small, isolated populations often lack genetic diversity, making them more susceptible to diseases and genetic defects. For instance, the California condor, once down to just 27 individuals, suffered from severe inbreeding, which increased its susceptibility to illnesses and environmental threats. Conservation efforts have since reintroduced captive-bred condors into the wild, but their narrow genetic base still makes the population fragile.

For these species, a single natural disaster, climate shift, or loss of habitat can have catastrophic consequences. Their inability to adapt to different habitats or food sources places them in a precarious position.

#4 Pollution and contamination

Pollution in our environment affects wildlife in a wide variety of ways that are quite unpredictable. Pollution contaminates air, water, and soil, and creates toxic environment that many species cannot tolerate. Pollutants disrupt ecosystems in a progressively worsening way and threaten the survival of numerous species.

Although biologists have been unable to isolate a single cause for the recent rapid decline in numbers and extinctions of many species, it appears that much of it is due to pollution.

Water pollution is especially harmful to aquatic species, as rivers, lakes, and oceans are often contaminated by toxic waste, agricultural runoff, and plastic debris. A striking example is the Declining Amphibian Phenomenon, in which amphibian populations worldwide have plummeted.

These chemicals, often pesticides and fertilizers, disrupt the development of young amphibians, making it nearly impossible for populations to thrive.

Plastic pollution is another growing threat, particularly in marine environments. Sea turtles, for instance, often mistake plastic bags for jellyfish, a key part of their diet. Ingesting plastic blocks their digestive systems, causing malnutrition or death.

Birds like albatrosses, which scavenge over oceans, often bring plastic debris back to their nests, unknowingly feeding it to their chicks. Recent studies estimate that 90% of seabirds (!) have ingested plastic. This is a sobering reminder of how pervasive this pollutant has become.

Air pollution poses a significant risk to birds and mammals, especially as it leads to acid rain and harmful ground-level ozone. Pollutants like sulfur dioxide and nitrogen oxides, released by industrial processes, mix with water vapor to form acid rain, which harms forests, lakes, and soil.

Fish populations in acidified lakes struggle as pH levels drop, and many plant species lose their natural resistance to disease and pests. For example, acid rain has contributed to the decline of trout in mountain lakes in the northeastern United States, where once-thriving fish populations have dwindled due to habitat degradation.

Chemical pesticides and industrial toxins have also led to significant declines in certain species. One well-documented case is the near-extinction of the Peregrine Falcon in Canada due to DDT. This pesticide, widely used until its ban in the 1970s, caused eggshell thinning in birds of prey, preventing successful hatching.

As a result, Peregrine Falcons and other birds of prey faced catastrophic declines. After DDT was banned, conservation efforts helped bring some populations back, but the incident highlighted how a single chemical could threaten entire species.

In the Sierra Nevada mountains, another type of pollution—excessive ultraviolet-B (UV-B) radiation—has damaged sensitive plant and animal species. The thinning of the ozone layer has led to increased UV-B exposure, causing cell damage and reducing the resilience of species that live in high-altitude, sunny areas. Species of frogs and other amphibians in the Sierra Nevada have experienced higher rates of deformities and population decline, partially due to this radiation.

Pollution impacts all levels of ecosystems, from the smallest microorganisms to apex predators. Toxic waste, chemical contaminants, and plastics disrupt natural food chains, reduce reproductive success, and increase mortality rates across species. These pollutants create lasting damage that takes decades to repair. Yes, it is a threat to a whole ecosystem not just individual species.

#5 Invasive species introduction and competition

Invasive species are a major cause of loss of diversity of both plants and animals. When a new species arrives with no natural predators to keep it in check, it can take over. And they often outcompete native species for resources.

A familiar example is the brown tree snake inadvertently arriving in Guam on a cargo ship following World War II. The venomous brown snake has decimated on virtually all of the local bird, fruit bat and lizard populations [8]. The snake population decimated local bird species – the Guam rail and the Micronesian kingfisher, both of which are now endangered or extinct in the wild. Just one snake species created a cascade of ecological disruptions.

In Australia, the introduction of the European rabbit in the 18^th century had severe impacts on native vegetation and animal species. Rabbits, which breed rapidly, quickly spread across the continent. Their populations have overgrazed land and depleted resources for native herbivores like the bilby and the greater stick-nest rat, both of which became endangered. Despite ongoing control measures, the rabbit population continues to threaten Australian ecosystems even to this day.

Asian carp is another invasive species causing significant ecological damage in North America’s waterways, particularly in the Mississippi River and its tributaries. Originally introduced to control algae in aquaculture farms, Asian carp escaped into the wild and spread quickly. These fish compete aggressively with native species for food, threatening the paddlefish and the smallmouth buffalo. Efforts to prevent Asian carp from reaching the Great Lakes continue, as their presence could further destabilize native fish populations and the fishing industry.

And one other example happened in the Great Lakes region of the United States, where the Zebra Mussel was accidentally introduced. Many of the native mussel species in the Great Lakes have now become threatened or endangered due to the presence of the highly competitive Zebra Mussel.

#6 Human-wildlife conflict

“If it moves, kill it.”

Is pretty much the mentality in rural America. And yet in a surprising twist, Los Angeles, a city and its suburbs home to 19 million people is an enclave where mountain lions live side-by-side with humans [9].

Mountain lions have been roaming the city for at least 30 years and The National Park Service has been studying them since 2002, curious how mountain lions survive in an increasingly fragmented and urbanized landscape [10].

A recent citing prompted this response from a 65-year old resident. “I was stunned and amazed at the beauty. I didn’t feel scared, it didn’t seem like it was aggressive,” said Moore, who was returning from checking on her neighbor’s small Yorkie while she was out of town. “We just had a kind of staring contest and I didn’t want to take off and have it chase me or something.”

Meanwhile, in rural Kenya, human-wildlife conflict takes a different form. Here, elephants frequently wander through villages and farmlands, sometimes destroying crops and threatening the livelihoods of local communities. For farmers, these elephants can bring financial ruin in a single night. In response, some communities have turned to innovative, non-lethal solutions. The “beehive fence” project, for instance, uses bees as a natural deterrent for elephants, which avoid the buzzing insects. This approach protects both the crops and the elephants. It reduces the need for lethal control and fosters coexistence of wild animals and humans.

In Australia, human-wildlife conflicts often involve kangaroos, who overgraze farmland and even cause traffic accidents in rural areas. As kangaroo populations grow and habitats shrink, encounters with humans increase, sometimes leading to culls to control their numbers.

For conservationists, finding a balance between kangaroo welfare and human needs remains a complex challenge. Programs that relocate kangaroos or use non-lethal deterrents aim to reduce conflict, though these methods are not always feasible on a large scale.

On the other hand, as our populations increase and more people move into areas where wildlife previously lived in abundance, new human-wildlife conflicts arise. Sadly, in many cases, wildlife is killed when they cause too big harm to farmers by hunting livestock or destroying crops.

For wildlife populations that have already been reduced due to loss of habitat and other issues, such conflicts can increase the chances that a species will become threatened or endangered.

#7 Disease

Diseases kill humans and animals alike. The Ebola virus killed 5,000 critically endangered western gorillas between 2002 and 2003 at the Lossi Sanctuary and other hundreds of gorillas in the Odzala-Kokoua National Park in 2003 and 2004 [12].

In Panama, a deadly chytrid fungus decimated 30 species of amphibians in the early 2000s. This fungus, which likely spread through the global wildlife trade and human activities, attacks the skin of amphibians, interfering with their ability to absorb water and oxygen. Many amphibian species, including the golden toad, vanished from their native habitats as the fungus spread across Central America. Without intervention, these species have little chance of survival in affected areas.

A deadly fungus from Europe, where it is harmless to bats has spread to North America killing 6 million bats and taking many species to the brink of extinction. The northern long-eared bat is believed to have declined by 99 percent due to the “white nose syndrome [13].”

It was another fungus species that destroyed the American chestnut tree, one hundred-foot hardwoods that once numbered in the billions in eastern forests of the United States, and a significant food source for a variety of wildlife, but which were virtually eliminated by a fungal pathogen accidentally imported into the United States from Asia [14]. Because the American Chestnut tree had evolved in conditions without the presence of the fungus, it lacked the natural resistance to survive.

Currently, there is ongoing research with the aim of creating a hybrid chestnut variety that is a cross between the American Chestnut and a variety of Chinese chestnut that is resistant to the chestnut fungus.

In some cases, diseases that spread to wildlife can be directly linked to human activity. The global wildlife trade—which often involves transporting animals over long distances in confined spaces—has introduced various pathogens to species with no natural immunity. Additionally, deforestation and habitat fragmentation force animals into closer contact with humans and livestock, increasing the likelihood of disease transmission between species.

#8 Low birth rate

It is believed that reproduction rates are a natural way of maintaining a population equilibrium. Some species do not reproduce very often, and they may have few offspring each time when they breed. Other species may take a number of years to become sexually mature, thus reducing their opportunity to breed over their lifetime.

Generally, larger mammals have longer lifetimes and lower birth rates and smaller animals like rodents who do not live as long produce many litters in succession [15].

Consequently, when large mammals suffer man-induced mortality, it takes longer for their populations to recover. A good example are marine mammals whose populations were diminished by commercial exploration.

#9 Lack of genetic diversity

If a population has low genetic variation, it cannot evolve in the face of changing environmental variables and will face an increased risk of extinction. For example, if a population does not have a gene that is resistant to a certain disease, that disease may wipe out the entire population in one fell stroke [17].

Some species, such as the Cheetah, maintain low genetic diversity, which makes them less able to adapt when faced with challenges such as overhunting or habitat loss. This low genetic diversity also makes them more vulnerable to diseases and expressions of negative genetic mutations.

Koalas are known to have low genetic variation as well [18]. This may be why they are showing high vulnerability to Chlamydia and the koala retrofit virus. Their vulnerability may also make it more difficult for koalas to adapt to global warming and human encroachment of their habitats.

The Florida panther, a subspecies of the cougar, is another example. Due to habitat loss and fragmentation in Florida, this population has become genetically isolated, resulting in low diversity and visible signs of inbreeding. Efforts to introduce cougars from other areas have improved genetic diversity slightly, but the species remains vulnerable to genetic diseases and environmental stressors. 

In plants, American elms faced a similar problem with Dutch elm disease, introduced from Europe in the 20^th century. Because American elms had low genetic diversity and lacked resistance to the disease, entire populations were devastated. Today, conservationists work to develop disease-resistant elms, but the historical lack of diversity left the species almost defenseless against a single pathogen.

Human activities, such as deforestation, urbanization, and agricultural expansion, often lead to habitat fragmentation. When species are confined to small, isolated areas, natural gene flow is restricted, which prevents populations from maintaining healthy genetic diversity. 

Additionally, the global wildlife trade exacerbates this problem by transporting small groups of animals for breeding or captivity, often resulting in genetic bottlenecks that reduce diversity further.

In a world where climate change and other human-induced environmental pressures are accelerating, low genetic diversity leaves species unable to cope with new conditions. Populations without genetic resilience are more susceptible to extinction from disease outbreaks, environmental stress, and rapid changes in their habitats. 

#10 A particular species is rare to begin with

Some species can be found only in certain areas. If there are only a limited number of individuals of a species that are in existence to begin with, and the environment changes, there is a lower probability that such a species will survive in the future.

Rare species can easily become extinct in the face of hunting. The Sumatran Tiger is an example of a rare species that was over hunted to the point of extinction, as there were a very limited number of individuals to begin with.

There are only 1,000 ili pika, a tiny mammal living in a remote mountain range in China. Rising temperatures have forced them to the mountain tops. It is believed that the air pollution of the Xinjiang region has contributed to their decline. Removal from their habitat, vulnerability to pollution, and vulnerability to predators as they are too quiet by nature to warn each other makes their survival as a species unlikely [19].

#11 Climate change

Climate change is changing habitats, temperature ranges, and entire ecosystems. Many species struggle to adapt quickly enough, and this can disrupt their natural behaviors, migration patterns, and breeding cycles, putting them at higher risk of extinction.

One clear impact of climate change is coral bleaching. Corals are sensitive to even small temperature changes. When the water gets too warm, corals lose the algae they rely on for energy. This causes them to turn white, or “bleach.” Without algae, corals often die, and entire reef ecosystems suffer. This affects fish, sea turtles, and many other species that rely on coral reefs for food and shelter.

In the Arctic, polar bears are losing their sea ice habitat. Polar bears use sea ice to hunt seals, their main food source. As the ice melts, they have to travel farther to find food, which leaves them exhausted and struggling to survive. Other Arctic animals, like seals and walruses, are also affected because they depend on stable ice to raise their young.

Shifting migration patterns are also a problem. Birds, for example, are migrating earlier in the spring or later in the fall. The European pied flycatcher is one such bird that relies on caterpillars for food when it arrives in northern Europe to breed. But now, because spring is coming earlier, the caterpillars peak before the flycatchers arrive, leaving the birds with little food. This is causing their populations to decline.

Climate change also affects animals that live in mountains, like the American pika. As temperatures rise, pikas move higher up to find cooler habitats. But as they reach the tops of mountains, they have nowhere else to go and face being trapped in shrinking habitats. This makes them very vulnerable to extinction.

Plants are also affected by climate change. Some, like cherry blossoms, are blooming earlier each year. This can disrupt the insects and animals that rely on these plants for food, like bees and butterflies. When the timing of life cycles is thrown off, it can lead to problems for both plants and pollinators.

Human-caused climate change is speeding up these changes faster than many species can handle. As habitats change, food sources are disrupted, and temperature ranges shift, many species face challenges that are difficult to survive. The effects ripple through ecosystems, affecting biodiversity around the world.

#12 Poaching

Poaching is a major problem for many animals, especially those with valuable body parts. Rhinos and elephants are two of the most affected. Rhinos are poached for their horns, which are used in traditional medicine and sold on the black market. Elephants are killed for their ivory tusks, which are carved into decorative items. High demand for these animal products drives poaching, even though these animals are protected by law.

The black market plays a big role in this problem. Despite bans on trading rhino horns and ivory, there is a strong illegal trade for these items, especially in parts of Asia. This demand leads to poaching in Africa and other regions, where poachers kill animals to make quick profits. The black market makes it hard to stop this trade, as people are willing to pay high prices for these products.

Poaching is driven by high demand and illegal trade. When animals and plants are removed from their habitats faster than they can recover, it threatens entire ecosystems. Strict protections and global efforts are needed to combat this problem and preserve biodiversity.

What Efforts Are Being Taken to Protect Endangered Wildlife?

Internationally, 199 countries have signed an accord to create Biodiversity Action Plans to address the conservation of threatened species and habitats [20].

CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora) is an international agreement between governments. Its aim is to ensure that international trade in specimens of wild animals and plants does not threaten their survival [21].

Many worthwhile organizations also exist to protect endangered species [22].

Efforts are made to find and rescue animals on the brink of extinction, bring them back to health, allow them to breed and raise their young in safe places, create a sustainable habitat and protect the habitat from encroachment, helping the endangered animals along until they reach numbers that give them a fighting chance of survival as a species.

You can help to save species from going extinct too.

How?