With overexploitation, populations can be reduced to a low level but may still recover.
Some species have a naturally low genetic diversity in their population and yet remain viable.
The bottleneck effect is when small populations may lose the genetic variation necessary to enable evolutionary responses to environmental change.
In small populations, the loss of genetic diversity caused by the bottleneck effect can be critical for many species, as inbreeding can result in poor reproductive rates.
The clearing of habitats has led to habitat fragmentation.
More isolated fragments and smaller fragments exhibit a lower species diversity.
Degradation of the edges of habitat fragments results in increased competition between species as the fragment becomes smaller.
The increased competition caused by the degradation of the edges of habitat fragments may result in a decrease in biodiversity.
To remedy widespread habitat fragmentation, isolated fragments can be linked with habitat corridors.
Habitat corridors allow movement of animals between fragments, increasing access to food and choice of mate.
The increased access to food and choice of mate facilitated by habitat corridors may lead to recolonisation of small fragments after local extinctions.
Introduced (non-native) species are those that humans have moved either intentionally or accidentally to new geographic locations.
Introduced (non-native) species that become established within wild communities are termed naturalised species.
Invasive species are naturalised species that spread rapidly and eliminate native species, therefore reducing species diversity.
Invasive species may well be free of the predators, parasites, pathogens and competitors that limit their population in their native habitat.
Invasive species may