Natural habitats are the physical, chemical and biological systems that support living things (i.e. plants, animals, fungi and microbes). More simply put, habitats are the places where these organisms live. Habitat is lost and degraded when natural or human-caused activities alter these places so that fewer species can live there. For example, when a section of forest is cut down and replaced with farmland or urban spaces, the living places of hundreds of species may be eliminated.
Although natural events such as landslides and earthquakes do alter the landscape, they generally occur in isolated areas and healthy ecosystems are able to recover from them. Human-caused habitat loss, on the other hand, is altering ecosystems on a global scale, often causing destruction that is irreversible, at least on a time scale that is of interest to society.
Habitat loss is not only a concern from the point of view of compassion for other species that share this planet. Humans are part of the great cycle of life on earth, and as such we depend on the overall function of natural systems for our own survival. Properly functioning natural systems create the air we breathe, break down our wastes, provide our food, purify our drinking water and ultimately supply all the materials we require for living. Each species plays an important role in its ecosystem. Habitat loss and degradation is the main threat to the world's endangered plants and animals, and is occurring at ever greater rates.
Despite this sobering picture, habitat loss is not always an inevitable consequence of human activities. There are ways to limit our impact on natural systems, for example by using principles of "smart growth" in urban planning (see More Information). Nevertheless, major changes and efforts are required to address this critical problem.