Encroachment is the spread of humans, transportation systems, utilities, buildings, and other development into natural areas. Encroachment leads to loss of habitat or changes in the natural ecology for plants, animals, fish, and other living organisms that live in the area. Whether it is due to development, hunting, mining, agriculture, or migrating populations, habitat encroachment increasingly exposes vulnerable humans to altered ecosystems and to new diseases.
Animals need access to food, water, and shelter to live and even plants need the natural conditions in soil, weather, and rainfall to which they have adapted. But with habitat encroachment, the ecosystems that support life are altered or eliminated. For example, draining a lake of all its water will kill the fish and other organisms living in the water and affect the health or migration patterns of birds or mammals that rely on the water for survival. Changes in the ecosystem can lead to overpopulation of some plants and animals that thrive in the new conditions and declining numbers of those that relied on the original environment. Most habitat encroachment can be attributed to increasing human populations and urban sprawl.
Biodiversity keeps natural systems in balance, so that different forms of life can survive and support one another. This means eventually humans are affected by their actions of encroaching on habitats. For example, if people continue to use all the fresh water, they will have less available to drink, and they will see declines in populations of fish for consumption. In general, human activities such as encroachment that lead to declining or extinction of species hurt crops and other food sources. Indigenous people are particularly threatened by these changes because they rely on local forests, grasslands, or other ecosystems for their survival.
One type of encroachment is habitat fragmentation. When roads, structures, or agricultural and logging operations divide a natural area such as grassland, it is considered fragmented. Division of the original area into smaller and sometimes isolated parcels are called habitat islands. Results can be loss of tree cover or disruption of animal migration routes. Fragmentation can also divide animal populations into smaller groups, making them more vulnerable to predators or disease. Animals might have trouble locating food and water. Sometimes, encroachment introduces new species of plants or animals, which then become invasive.
The ecosystems on Earth, which have evolved over millions of years, support the diverse and complicated forms of life on the planet. Since the earliest reports of human life, the diverse ecosystems have provided food, energy, water, and even medicine for people. In more recent history, especially in the twentieth century, the natural sources for plants, animals, and people have changed and declined on Earth. In some areas, such as Europe, hundreds of years of grazing livestock and harvesting meadows have led to encroachment on local forests and vegetation. These practices have caused an imbalance in the types of plants growing in any given area and an imbalance in the animal life the land supports. In the 1990s, about 94 million acres of global forest area were lost because people converted the forest to agricultural use or urban settlement. This loss amounted to nearly 2.4% of total forests.
Logging and unsustainable agricultural practices, such as deforestation for monoculture as in the palm oil industry in Indonesia and subsistence farming, are among the leading causes of habitat loss. Others are mining, climate change, and pollution. Overexploitation, which is hunting and fishing in an unsustainable way, also adds to habitat degradation. Development in suburban areas also causes encroachment. Developers clear land of trees and other vegetation to build homes or commercial properties. Building along shorelines often includes erecting walls or jetties to protect the shoreline, but they also affect wave energy and sediment layers nearby.
Even when habitats are not entirely lost, they can be altered so much by human encroachment that they fail to support natural life. The encroachment can lead to lack of food or drinking water, causing diseases of the stomach, along with undernutrition, malnutrition, or dehydration. Humans also affect habitats by accidentally introducing organisms not native to the area. For example, bringing plants native to other parts of the world into a new community can lead to new pests that affect crops, or the introduction of invasive plants that choke out native plants essential for the local habitat. Declining populations of plants or animals in the area typically are the first symptoms of habitat encroachment. Logging or other removal of vegetation can lead to increased erosion, affecting nearby water flow and quality. Agricultural practices might cause runoff of pesticides and livestock waste, which can pollute freshwater supplies for people and fish and introduce diseases.
Prevention of encroachment on habitats and sustainable practices in hunting, farming, logging, and development can stop many diseases and other health issues from occurring. Given that only about 1% of animal viruses are known to people, outbreaks and death in humans and animals can occur before treatments or preventing measures are developed. For example, when the Ebola fever outbreak occurred in 2014, there was no treatment for the disease in people, and as of 2018 no treatment was available. Doctors can only help relieve symptoms and results of the fever.
Many of the health issues from habitat encroachment can be prevented or lessened with adequate laws and enforcement of laws. For example, control of hunting and fishing practices, and especially poaching, can slow encroachment on and decline of native species. The U.S. Endangered Species Act, introduced in 1973 in the United States, was designed to prevent declining populations of individual species of animals but was not very successful. A more comprehensive approach might be to introduce laws protecting ecosystems and habitats that support several species and people. International treaties have been signed by some countries to help maintain ecosystems and protect native species.
The Centers for Disease Control and Prevention and the World Health Organization have led efforts to prevent emerging infectious diseases. These prevention efforts are expressed through education and vaccination and in helping countries and regions at risk develop plans to prevent and control health problems from habitat encroachment. They also have responded to threats to humans from new diseases such as emergent severe acute respiratory syndrom (SARS) and Middle East respiratory syndrome (MERS). Efforts to control Ebola virus disease include tracking cases, laboratory support for testing, and education. Countries have banded together to develop early warning systems for emerging zoonotic disease outbreaks.
People around the world, especially those heading industries that use natural resources, are being encouraged to join in ensuring sustainable, long-term approaches to dealing with habitat encroachment, and eventually prevent disease outbreaks and other health effects of encroachment. Communities and individuals can support seed banks, which preserve seeds from endangered plant species, and wildlife farms that offer habitats for animals.
Individuals can help prevent unnecessary damage to habitats by learning more about local natural habitats, by reducing pollution, and by planting native species on their properties to provide habitats where encroachment has begun. It also helps to consider when building on one's property or supporting development in a community the possible impact of these actions on habitats. Everyone can be aware of and discourage introduction of invasive plant or animal species. Communities can work with public health officials to minimize the chance that diseases and other health effects of habitat encroachment become outbreaks and serious public health crises.
See also Ebola virus disease ; Globalization and emerging diseases ; HIV/AIDS .
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Teresa G. Odle, BA, ELS