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• 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 — small populations may lose the genetic variation necessary to enable evolutionary responses to environmental change
• bottleneck - In small populations, this loss of genetic diversity can be critical for many species, as inbreeding can result in poor reproductive rates
• The clearing of habitats has led to habitat fragmentation.

  Degradation of the edges of habitat fragments results in increased competition between species as the fragment becomes smaller.

  This may result in a decrease in biodiversity
• More isolated and smaller fragments exhibit a lower species diversity
• To remedy widespread habitat fragmentation, isolated fragments can be linked with habitat corridors
• The corridors allow movement of animals between fragments, increasing access to food and choice of mate.

  This 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
• naturalised species - Those that become established within wild communities
• Invasive species are naturalised species that spread rapidly and eliminate native species, reducing species diversity.

  They can be free of the predators, parasites and competitors that limit their population in their native habitat. They can prey on native species, outcompete them for resources