Topic 2 - Threats to wildlife

HideShow resource information

Unsustainable exploitation for human gain

How humans threaten wildlife - deliberate exploitation

Food 

A wide range of species have become rarer or even extinct because they have been hunted and overexploited for food. These include the dodo, passenger pigeon, cod, swordfish, tuna and many sharks.

Fashion

Many species have been collected or hunted because people find their skins, shells or horns attractive.

  • Crocodiles and alligators - leather for bags and shoes.
  • Turtles - shells for ornaments and the frames for glasses.
  • Rhino - horn for dagger handles.
  • Shellfish - seashells for tourist souvenirs.
  • Elephants - ivory.
  • Wild cats - fur coats.
1 of 11

Unsustainable exploitation for human gain

How humans threaten wildlife - deliberate exploitation

Fashion

Case study - the snow leopard

Snow leopards are threatened by habitat loss and loss of prey species, but the main threat is hunting for their skins. A snow leopard coat would require 6-10 skins and could be worth £30,000 on the black market.

Pets and entertainment

Some popular pets include:

  • Tortoises
  • Tropical fish
  • Parrots
  • Lizards
  • Snakes
2 of 11

Unsustainable exploitation for human gain

How humans threaten wildlife - deliberate exploitation

Pets and entertainment

Case study - the yellow-headed parrot

Yellow-headed parrots are social, easy to tame and mimic human voices well, which makes them very popular in the pet trade. They are protected by CITES Appendix I, but are still poached illegally by cutting into the nesting trees to take eggs and chicks. The population has dropped by 95% since the 1970s.

Sea animals such as dolphins and orcas, are collected for public entertainment in dolphinaria. Some plants are collected as house plants, including 'air plants', some tropical exotics and many insectivorous plants.

3 of 11

Unsustainable exploitation for human gain

How humans threaten wildlife - deliberate exploitation

Furniture and ornaments

  • Mahogany and teak - furniture 
  • Ivory - white piano keys
  • Ebony wood - black piano keys
  • Coral - jewellery
  • Shells from turtles and tortoises - jewellery

Traditional medicines

  • Tigers - different parts of the body are used as cures for the different problems: claws as a sedative; the tail for skin diseases; dung for alcoholism; brain for laziness; whiskers for toothache.
  • Snakes - traditional medicines are made from snakes in the belief they will cure arthritis and skin disease.
  • Bear bile - bears are caught and kept in cages so the bile can be drained from their gall bladders. It is used for sufferers of fever and liver disease.
4 of 11

Unsustainable exploitation for human gain

How humans threaten wildlife - deliberate exploitation

Other products

  • A very fine oil has been extracted from whale blubber and from the spermaceti in the heads of sperm whales.
  • It was used until the 1970s in the manufacture of candles, soap, lubricating oil and cosmetics. 
  • It has now been replaced with other ols including oil from the jojoba plant.
5 of 11

Introduced species

How humans threaten wildlife - introduced species

Introduced species

  • The community of species found in an area will be adapted to their abiotic and biotic surroundings. An introduced species may have a competitive advantage, which means that the indigenous species cannot survive.
  • Many of these introductions have had a catastrophic effect on the indigenous species. This is especially true for isolated areas such as islands where there is an odd community of species that managed to colonise from other land masses a long way away and have evolved from a few orignial species to occupy a wide variety of available niches.
  • They may have evolved in the absence of mammal predators and are not adapted to cope with them if they are introduced.
6 of 11

Introduced species

How humans threaten wildlife - introduced species

Predators

  • In UK rivers, water voles are killed by American mink that escaped from fur farms.
  • Many species in Autralia are threatened by cane toads that were introduced from South America to control insect pests in sugar cane plantations. They are general predators, eating lizards, insects, small marsupials and ground-nesting birds.
  • The small Asian mongoose was introduced to Hawaii to control rats that were pests in sugar cane fields. They have devastated endemic ground-nesting birds.
  • The ground-nesting birds on many oceanic islands such as New Zealand, Australia and Hawaii are threatened by introduced cats, rats, pigs and dogs.
  • The vegetation of many islands, such as Round Island in the Indian Ocean, has been seriously damaged by introduced herbivores such as rabiits and goats. They were introduced deliberately by sailors hundreds of years ago so they would be 'lving larders' for future visits.
7 of 11

Introduced species

How humans threaten wildlife - introduced species

Competitors 

  • They grey squirrel was introduced into the UK from North America in the 19th century. It out-competes the indigenous red squirrel as it is better at using the available food. It is better at digesting acorns from oak trees. Being larger it can compete successfully for nest sites. It also carries the squirrel pox virus that kills red squirrels.
  • Rhododendrons were introduced to the UK from Asia for their ornamental flowers and as cover for game birds. They are very invasive and, being evergreen, they shade the ground and reduce the growth of native vegetation.
  • The harlequin ladybird was introduced to Europe from Asia, reaching Britain in 2004. It is a voracious predator and out-comoetes indigenous ladybird species. They also predate other ladybird species.
8 of 11

Introduced species

How humans threaten wildlife - introduced species

Disease

  • Elm trees in Europe and North America have been killed by a fungus that was accidentally introduced from Asia and has been spready by a bark beetle.
  • More than half the indigenoous bird species of Hawaii are endangered or have become extinct in the last 100 years as a result of habitat loss and the impact of introduced species. Pigs, cates, snakes, rats and mongoose are predators of ground-nesting birds. Hawaiian honeycreepers are threatened by malaria that is carried by introduced mosquitoes.
  • The signal crayfish was introuced to the Uk from North America to provide food. It carries a fungus disease that kill the indigenous white-clawed crayfish.
9 of 11

Habitat change

How humans threatened wildlife - habitat change

Changes in abiotic factors

  • Fish such as trout must lay their eggs in gravel in well-oxygenated parts of rivers where the water is flowing fastest - rivers that are straightened to reduce the risk of flooding, may become unsuitable for trout. 
  • Crayfish and sensitive fish species - acid rain increases the acidity of rivers and lakes. 
  • Species of river plants - human land-uses, such as farming or mining, may increas the turbidity of the river. This may reduce light penetration and prevent plants from photosynthesising.

The changed conditions may not kill all the individuals of a species. Hiwever, if the death rate increases to a point where it is greater than the birth rate, then the population will decline.

10 of 11

Habitat destruction

How humans threaten wildlife - habitat destruction

Habitat destruction

Major changes to a habitat may cause the entired community of species to die out. Examples include:

  • Deforestation either to created farmland or to exploit timber.
  • Flooding caused by reservoir construction.
  • Mining.
  • Urbanisation.
11 of 11

Comments

gokyscunt

Great information in these slides, really helped me out with my Environmental Studies A- Level project, there are a few spelling mistakes throughout but they dont affect the quality of the information

Similar Environmental Science/Studies resources:

See all Environmental Science/Studies resources »See all The Living Environment resources »