12-3 Extinction Threats From Habitat Loss and Degradation

What Is the Role of Habitat Loss and Degradation? Creating Homeless Specie

Conservation biologists some- times summarize the main secondary factors leading to premature extinction using the acronym HIPPO:

  • Habitat destruction and fragmentation

  • Invasive (alien) species

  • Population growth (too many people consuming too many resources)

  • Pollution

  • Overharvesting

According to biodiversity researchers, the greatest threat to wild species is habitat loss, degradation, and fragmentation. In other words, many species have a hard time surviving after we take over their ecological “house” and food supplies and make them homeless.

According to the Nature Conservancy, the major types of habitat disturbance threatening endangered species in North America are, in order of diminishing importance:

  • Agriculture

  • Commercial development

  • Water development

  • Outdoor recreation (including off-road vehicles)

  • Livestock grazing

  • Pollution

What Is the Role of Habitat Fragmentation? Isolating and Weakening Populations of Species

Habitat fragmentation occurs when a large, continuous area of habitat is reduced in area and divided into smaller, more scattered, and isolated patches or “habitat islands.”

This divides populations of a species into smaller and more isolated groups that are more vulnerable to predators, invasion by more competitive species, disease, and catastrophic events such as a storm or fire.

Case Study: How Do Human Activities Affect Bird Species? A Disturbing Message from the Birds

Approximately 70% of the world’s 9 800 known bird species are declining in numbers, and about one of every eight bird species is threatened with extinction, mostly because of habitat loss and fragmentation.

Non-native species are the second-greatest threat to birds. They include bird-eating cats, rats, brown-tree snakes, and mongooses.

Other threats to birds are oil spills, exposure to pesticides, herbicides that destroy their habitats, and swallowing toxic lead shotgun pellets left in wetlands and lead sinkers left by anglers. Poorly regulated illegal hunting and capture also take a heavy toll.

Conservation biologists view this decline of bird species as an early warning of the greater loss of bio- diversity to come. The reason is that birds are excel- lent environmental indicators because they live in every climate and biome, respond quickly to environmental changes in their habitats, and are easy to track and count.