Human impact on the environment

Endangered species

A species that due to a loss of habitat or rapid decrease in population numbers is at risk of extinction

When is a species described as extinct

When all members of the species are dead

Examples of species extinct due to humans

Moa, giant ground sloth, passenger pigeon

What proportion of the planet’s marine fish species rely on coral reefs

1/3

How many mass extinction events have occurred in history

5, due to catastrophic change such as:

• low global temperature

• shortage of dissolved oxygen in oceans

• ocean acidification

6 potential causes for extinction of a species

• Natural selection due to selection pressures

• Loss of habitat

• Pollution

• Overhunting by humans

• Introduction of new competitors

• Non-contiguous pollutants

Extinction by natural selection

Natural selection causes populations to decrease as those less suited to environmental change die or reproduce less successfully. Human activities cause habitats to change faster than new advantageous mutations arise

Extinction by non-contiguous populations

If groups of individuals are isolated from each other, they can’t interbreed so each group functions as a separate population. Genetic diversity decreases so the populations are less able to adapt to environmental change

Extinction by loss of habitat

Examples of habitat loss causes are deforestation, drainage of wetlands, hedgerow loss and crops sown in Autumn so birds can’t build nests.

Extinction by overhunting by humans

• Trophy hunting

• Traditional medicinal practices (rhino horn)

• Bush meat industry

• Overfishing

• Agricultural exploitation

Extinction by competition from introduced species examples

• 17th-century Madagascar: the dodo was driven to extinction as rats carried on European ships ate dodo eggs

• North American signal crayfish invaded UK streams/rivers and native crayfish is out-competed

• Red squirrels in UK declined due to being out-competed by North American grey squirrel

Extinction by pollution

• Accidental discharge of oil in the sea causes deoxygenation of water, coats surface animals in oil, birds feathers stick together so they lose insulation, washes up on shore and is ingested by shore-dwelling animals

• PCBs are ingested with food. They’re neurotoxins, carcinogens and hormone disruptors. They were continuously dumped into a quarry west of Cardiff and are still detected in wastewater from the site.

IUCN levels of vulnerability to extinction

• extinct EX

• extinct in wild EW

• critically endangered CR

• endangered EN

• vulnerable VU

• near threatened NT

• least concern LC

• data deficient DD

• not evaluated NE

Conservation

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

6 ways conservation can be achieved

• Protection of habitats

• Protection of endangered species

• International cooperation

• Species reintroduction

• Gene and sperm banks

• Seed banks

Conservation by protection of habitats

Protecting habitats protects the species that live there + communities act as living gene banks. Small nature reserves and larger ones, such as SACs, SSSIs, MCZs, SPA. They have varying levels of legal protection and may be managed/monitored by wardens

Conservation by international co-operation

International co-operation restricts trade in ivory harvesting, whaling etc. International law allows some countries to practice ‘scientific’ whaling or cull whales for food in indigenous communities

Conservation by gene banks

Endangered species are protected and entered into breeding programmes in specialised zoos and botanic gardens. Records of matings are kept so genetic diversity can be increased by deliberate choice of parents

Conservation by sperm banks

Sperm banks are used to store genes of economically important animals and threatened species. Rather than moving animals, sperm samples can be sent around the world to use in breeding programmes in other zoos

Conservation by seed banks

Seed banks maintain stocks of seeds of traditional varieties and vulnerable species in highly controlled conditions, often in liquid nitrogen. Seed banks can have high levels of protection as they are viewed as a potential source of food in case of catastrophic environmental degradation.

Conservation by species re-introduction

Successful breeding programmes are followed by reintroduction to former habitats. Examples are the red kite in the Chilterns, the chough in Cornwall and the giant condor in California

Conservation by education

• Global organisations e.g. WWF create public-awareness campaigns.

• In the UK, the Countryside Commission advises government/groups whose activities affect wildlife and their habitats. Produced publications, proposes ecosystem management schemes and establishes nature reserves

Conservation by legislation

The EU Habitats Directive imposed a range of measures to protect habitats and enhance biodiversity throughout Europe, preventing overgrazing, overfishing, hunting of game, collection of bird eggs, picking wild flowers and plant collecting

Conservation by ecotourism

Ecotourism recognises that mass travel is harmful globally and to specific habitats. It aims to:

• Contribute to conservation efforts

• Employ local people + give money back to local communities

• Educate visitors about local environment and culture

• Co-operate with local people to manage natural areas

4 reasons conservation of gene pools is important

• Many plant species yet to be discovered + may contain chemicals that could be used in future medicines

• Protection of potential future food sources

• Some alleles may provide selective advantages, preventing extinction

• Each species and its genes are precious

Ethical reasons for conservation

Each species represents a particular combination of genes and alleles adapted to a particular environment and it’s considered that the uniqueness of each is intrinsically valuable

Reasons for conservation- agriculture and horticulture

Plants + animals used in agriculture/horticulture have been developed from those in the wild. Selective breeding increases genetic uniformity, with the loss of rarer alleles. Qualities such as resistance to cold, disease and drought need to be bred back into cultivated varieties

Reasons for conservation- potential medical uses

antibiotics are largely derived from fungi but many other drugs are synthesised from plants. Quinine is used to treat malaria and it comes from the bark of Cinchona tree. Logic dictates that there are potential drugs that could be of immense value, these may be in undiscovered species or ones at risk that haven’t been investigated

Agricultural exploitation

The increase in efficiency and intensity of food production in order to meet growing demands

Agricultural exploitation: effects of monocultures

• less habitats for insects so lower biodiversity

• less genetic diversity so increased risk of mass disease spread

• pest populations can increase more rapidly

• Minerals extracted from same depth so inorganic fertiliser use increased

Agricultural exploitation: effects of overgrazing by cattle and sheep

Hooves compact the soil, driving out air and preventing water drainage. Roots can’t as easily penetrate the soil so crops struggle to grow. Nitrification is decreased as it requires oxygen.

Deforestation

The removal of trees from land which is subsequently used to grow crops or provide space for cattle

Reasons for deforestation

• Timber for building and fuel

• Land cleared for farms or urbanisation

• Roads built to connect areas

6 consequences of deforestation

• Loss of biodiversity

• Climate change

• Habitat loss

• Soil erosion

• Desertification

• Lowland flooding

What do managed forests involve

• Coppicing

• Selective cutting

• Long rotation line

Overfishing

The excessive fishing of an area at a rate which exceeds potential replenishment of species

9 methods employed to regulate fishing

• Use lines not nets

• Regulate net (mesh) size

• Fishing quotas

• Exclusion zones

• Avoid overfished species

• Fish non-traditional species

• Limiting fishing fleet sizes

• Marine Stewardship council certification

• Fish farms

Fish farming

The breeding of fish commercially in enclosures for food to combat overfishing

4 problems with fish farming

• Rapid spread of disease

• Escape of farmed fish - spread disease and outcompete wild

• Bioaccumulation of pesticides

• Farmed fish contain high concentrations of toxic chemicals e.g. dioxins

Sustainabilty

Using resources in a way that also maintains them for future generations

3 factors monitored in environmental monitoring

• Air quality

• Water quality

• Soil quality

Planetary boundaries

A set of 9 limits proposed by a group of environmental and Earth system sciences within which humanity can operate without risk of irreversible damage to the planet

Which 4 planetary boundaries have been crossed

• Climate change

• Biosphere integrity

• Land system change

• Biogeochemical flows

Which 2 planetary boundaries are avoidable

• Ocean acidification

• Fresh water consumption

Which planetary boundary has been avoided

Ozone depletion in the stratosphere

Which planetary boundaries aren’t quantified

• Atmospheric aerosols

• Introduction of novel entities