Habitat Destruction

Of the Earth's living animal and plant species assessed by the IUCN Red List, more than 41,000 (or 28%) of them are at risk of extinction, including 27% of all assessed mammalian species and 41% of assessed amphibian species. Many of these species were push to the brink by anthropogenic pressures over the past few centuries, most notably habitat destruction.

Habitat Destruction Definition

Habitat destruction occurs when an ecosystem’s habitat is destroyed, polluted, or otherwise damaged to the point that the native wildlife species can no longer survive there. While in historic times hide-hunting and eradication efforts were the major threats to wildlife, in the late 20^th and early 21^st centuries habitat destruction became the greatest threat to the survival of many species and the Earth’s biodiversity levels. Habitat destruction is a particularly pressing problem in portions of Africa (e.g., Nigeria), South America (e.g., Brazil), and Southeast Asia (e.g., Indonesia and Thailand), where expanding human populations, resource exploitation, and urbanization have resulted in a widespread removal of habitat and eradication of many native species.

Effects Of Habitat Destruction

Habitat destruction has numerous adverse effects on both humans and non-human animals. The loss or fragmentation of a species’ habitat can result in a loss of breeding habitat and shelter, thus bringing wildlife in closer proximity to and, in numerous instances, into conflict with humans. This often results in the eradication of the species from their former habitat, particularly when large and potentially dangerous predators are involved. This is why large predators typically experience the most dramatic declines in areas heavily populated by humans.

Habitat destruction also results in the loss of essential resources for the survival of native species, including vital vegetation for herbivores and prey species for predators. This destruction also often occurs alongside increased levels of pollutants, which causes further declines in biodiversity and threatens the human population with illness and disease.

The widespread and large-scale loss of forest habitat also exacerbates anthropogenic climate change, which is already having a negative impact on both human and wildlife populations worldwide, due to rising sea levels, increased temperatures, and increasingly unpredictable weather. Habitat destruction can also cause potentially catastrophic geological changes to an ecosystem, resulting in diverted waterways and rendering communities more at risk of dangers such as flooding and tsunamis. The tropical regions of the world suffer the highest levels of habitat destruction due to increased human population densities and resource exploitation.

Causes Of Habitat Destruction

Though natural events can and do cause habitat destruction, the most constant and severe causes of habitat destruction are anthropogenic (man-made).

• Natural events which may cause large-scale habitat destruction include tsunamis (which may change the entire landscape of some islands), volcanoes, hurricanes, and rarer events, such as meteor impacts.

• Anthropogenic causes are much more common and frequent. Most of these causes are related to resource exploitation to satisfy the needs of an exponentially increasing, unsustainable human population. The indigenous people and wildlife of tropical developing countries often bear the greatest brunt of these activities.

In addition to resource exploitation, housing and transportation are major causes of anthropogenic habitat loss. As communities continue to expand into what was formerly untouched wilderness, roads and freeways are built into these areas, resulting in increased rates of wildlife being hit by vehicles (roadkill) and fragmentation of habitat. This has been very damaging to large mammalian predators that have large territories, as dangerous road crossings shrink their territory and put them into conflict with other individuals, often resulting in death and inbreeding.

Examples Of Habitat Destruction

The following are a few different examples of habitat destruction, one natural and three anthropogenic.

The 2004 Indian Ocean tsunami

Tsunamis can result in widespread loss of habitat, particularly in areas already damaged due to anthropogenic causes. During the 2004 Indian Ocean tsunami that resulted in the deaths of at least 227,898 people, many portions of Southern and Southeast Asia experienced the loss of coastal habitat.

Over the past two decades, foreign companies have destroyed much of one of the last bastions for wildlife in Cambodia. The country’s Botum Sakor National Park is home to a wide variety of threatened species, including species listed as critically endangered or endangered, such as the Sunda pangolin (Manis javanica), Siamese crocodile (C. siamensis), pileated gibbon (Hylobates pileatus), and Asian elephant (Elephas maximus). Even the last Cambodian individuals of the aforementioned saltwater crocodile were believed to have resided within Botum Sakor.

The Cambodian government sold large portions of the national park to foreign-owned companies to use for development, including agricultural land and entertainment venues, as well as a large highway and an airport. In addition to the unknown toll on the local wildlife, this also resulted in a dozen local human communities being moved to new locations. The resulting widespread deforestation (Fig. 1) and the influx of workers have likely had a devastating impact on biodiversity levels within the park.

Figure 1: The loss of forest cover in Botum Sakor National Park over the past two decades. Source: Monga Bay

Fragmented Mountain Lion Populations In Southern California

Southern California is one of the most densely populated places in the United States and the world, with a population of over 10 million in Los Angeles County alone. To put that into perspective, the entire country of Australia is home to less than 26 million people!

As you can imagine, this has put the native habitat under severe pressure. The biological landscape of Southern California is drastically different than it was two centuries ago, when brown bears (Ursus arctos), grey wolves (Canis lupus), and even jaguars (Panthera onca) roamed the region’s oak woodlands. Today, the mountain lion (Puma concolor) is one of only two large predatory mammals (the other being the black bear, Ursus americanus) still remaining in Southern California.

The mountain lion’s habitat has been severely fragmented by the region’s large and congested freeways and its ever-expanding suburban communities. Since male mountain lions have vast home ranges, this often results in the individuals needing to make difficult decisions - remain in the fragmented habitat and risk potentially deadly conflict with other males, or venture out onto the freeways in an effort to reach new habitat.

When these mountain lions attempt to cross these major Southern Californian freeways (such as the 5 or the 101), they are often struck and killed by vehicles. In fact, along with ingesting rodenticide from poisoned prey species, roadkill is the major cause of mortality among Southern Californian mountain lions. This fragmentation has also resulted in a limited gene pool and increased levels of inbreeding, particularly within the Santa Monica Mountains. Thankfully, in 2022, a large wildlife corridor over the 101 freeway began construction, specifically to address this issue (Fig. 2).

The Border Wall, Habitat Fragmentation, And The Future Of The Jaguar In The United States

The wall along the southern border separating the United States from Mexico has been hot topic politically over the past decade, but the project has also had potentially devastating ecological consequences.

The jaguar once ranged from Southern California to at least as far east as Louisiana and the Mississippi River, but was virtually eradicated in the United States by the mid-20^th Century due primarily to hunting pressures. Today, only the occasional individual is spotted in southeastern Arizona and southwestern New Mexico, usually a male wandering up from the Sonora state of Mexico (Fig. 3). The construction of the border wall, particularly along the border of these two states, is likely to significantly diminish any hope of jaguars becoming reestablished in the United States without active reintroduction.

Figure 3: A jaguar known as "El Jefe" has been captured on trail cameras in southeastern Arizona several times over the past decade. Source: Wikipedia

In addition, this region is also an important transition zone between North American and Central/South American wildlife. In addition to jaguars, these portions of Arizona and New Mexico also have some other wildlife typically associated with the tropics, including coatis (Nasua narica), peccaries (Dicotyles tajacu), and even the rarely seen ocelot (Leopardus pardalis). In fact, boa constrictors (Boa sigma) are found less than 200 km south of the border! These species are threatened with restricted gene flow due to the border wall.

Many solutions have been proposed to minimize the destruction of habitat, but their success is largely dependent on effective enforcement. The expansion and better protection of national parks and protected areas is one potential solution, though this can be susceptible to poor enforcement and being auctioned off to the highest bidder (as was seen in Cambodia and many other areas).

Another potential solution is making agricultural practices more environmentally friendly and sustainable, by making them function within and as part of the habitat. This may involve creating forested wildlife corridors within oil palm plantations or building these plantations on unused farmland, rather than by destroying important forest habitat. However, while this may help some species, it does not solve the problem large predators face, as they are likely to attack and prey upon workers in these agricultural lands regardless. Other solutions well beyond the scope of simple conservation include mitigating human population growth and unsustainable lifestyles.