Human Impact

Biodiversity

Refers to 2 aspects of organisms in a given environment - the number of species and the number of organisms within each species

Reasons for species becoming endangered or extinct

Natural selection

Deforestation

Habitat destruction

Loss of hedgerows

Pollution

Hunting and collecting

Competition from domestic animals

Reason for natural selection being a reason for species endangered or extinct

Existing species do not have the ability to survive in a changing environment e.g. sabretooth cat, woolly mammoth

Reason for deforestation being a reason for species endangered or extinct

Loss of habitat e.g. birds and insects

Reason for habitat destruction being a reason for species endangered or extinct

Such as deforestation, drainage of wetlands and loss of hedgerows e.g. birds such as skylark, insects and reptiles

Reason for loss of hedgerows being a reason for species endangered or extinct

Loss of habitat for insects, nesting birds and reptiles

Loss of food for many species

Loss of varying light intensity and water availability for diverse plants

Reason for pollution being a reason for species endangered or extinct

Such as PCBs (which are toxins that can be ingested) and oil spills.

Oil floats prevent oxygenation of surface water - animals that break through surface are covered by a film of oil. e.g. shore-dwelling animals, birds and plants.

Reason for hunting and collecting being a reason for species endangered or extinct

Overhunting by humans include trophy hunting some traditional medical practices e.g. the use of rhino horns, the bush meat industry in which primates among others are killed for food, overfishing and agricultural exploitation.

Reason for competition from domestic animals being a reason for species endangered or extinct

The dodo was driven to extinction by rats brought on European ships ate the dodo eggs.

The north American signal crayfish has invaded UK streams and rivers and the native crayfish, which is smaller, has been out-competed.

Red squirrels out-competed by grey squirrels

Conservation

The protection, preservation, management and restoration of natural habitats and their ecological communities, to enhance biodiversity while allowing for suitable human activity.

Conservation methods

SSSIs (sites of special scientific interest)

Restrictions on trade

Zoo breeding programmes

Sperm banks/seed banks

Reintroductions

How do SSSIs enhance biodiversity?

Protecting habitats protects the species that live there and communities act as living gene banks. These sites have varying levels of legal protection.

How do restrictions on trade enhance biodiversity?

International cooperation can restrict trade in products from endangered animals. For example, CITES has been in effect from 1975 and its aim is to ensure that trade in specimens of animals and plants doesn’t threaten survival of species in the wild.