Habitat fragmentation

Lore & Background

Habitat fragmentation includes five discrete phenomena: reduction in total area of habitat, decrease of the interior:edge ratio, isolation of one habitat fragment from other areas, breaking up of one patch into several smaller patches, and decrease in average size of each patch. The term is debated in scientific literature, with some applying it strictly to habitat being cut into smaller pieces without significant area loss, while others include habitat loss under the same term. Causes include natural processes like volcanism, fire, and climate change, as well as human activities such as agriculture, rural development, urbanization, and creation of hydroelectric reservoirs.

Reader's Guide

Habitat fragmentation is considered an invasive threat to biodiversity, affecting a large number of species. It reduces biodiversity by 13 to 75% and impairs key ecosystem functions by decreasing biomass and altering nutrient cycles. The effects damage the ability of species, such as native plants, to adapt to changing environments, preventing gene flow between generations, especially in smaller populations. However, a review of empirical studies found that 76% of reported significant effects of fragmentation per se on species occurrences, abundances, or diversity were positive, while 24% were negative. The negative effects of habitat loss are generally viewed as much larger than those of fragmentation, but the two are heavily connected. Fragmentation also leads to edge effects, altering microclimates and increasing fire risk, and can cause population dynamics to vary asynchronously, preventing rescue effects in isolated fragments.

Did You Know?

• Habitat fragmentation consistently reduces biodiversity by 13 to 75%.
• Fragmentation can prevent gene flow from one generation to the next, especially for species in smaller populations.
• Microclimatic changes from edge effects can increase the likelihood of fires.