Brent Cornell

    
Biodiversity within a given ecosystem will be affected by a number of biogeographic factors:

• Larger habitats tend to promote biodiversity better than smaller habitats (more available niches = less competition)
• Ecology at the edges of ecosystems is different from central areas (e.g. more sunlight, more wind, etc.)
• This is known as the edge effect, whereby species distribution is influenced by the divergent environmental conditions
• Edges tend to have greater biodiversity, as different habitats with different abiotic factors exist in close physical proximity
• However edges tend to have more competition than central regions, which may restrict survival prospects of certain species
• Habitat corridors between parts of a fragmented habitat can connect disparate regions to improve genetic diversity

These principles are routinely applied when setting aside land as a nature reserve to improve the conservation of biodiversity

General Biogeographic Principles of Nature Reserves

    
Island Size

The biodiversity of an island is typically proportionate to island size (i.e. larger islands have greater biodiversity)

• Larger islands support a greater range of habitats (and hence more available niches for species to occupy)
• Larger islands can sustain higher population numbers for each species (increases species evenness)
• Larger islands have greater productivity at each trophic level, leading to longer and more stable food chains

Relationship between Island Size and Biodiversity

Edge Effect

The diversity of species within a given environment changes with proximity to the ecosystem’s boundaries (edge effect)

• Biodiversity may be greater at the border between two ecosystems as different abiotic factors favour certain species
• However certain species may not be able to thrive under these conditions and instead must occupy more central regions
• The effect of edges on biodiversity will be greatly influenced by the particular conditions caused by the ecological disturbance

Relationship between Edge Effect and Biodiversity (South Brazil)