1.6 Human Impact On The Environment

**Extinction**

The death of the last indivisual in a species

What is the effect of **extinction?**

A **loss of species** and a decrease in biodiversity

Define the term **endangered species**

A species that is seriously at risk of extinction

Give reasons a species may go extinct

• Destroying habitats – e.g. removing hedges, draining wetlands, deforestation.

• Pollution of the environment e.g. PCBs (polychlorinated biphenyls) oil and pesticides.

• Introduction of alien species to an ecosystem - These species may out-compete native species for food and space. In addition, they might have no natural predators or grazers to control the population. They may also carry diseases that affect native populations.

• Monoculture – growing large numbers of the same, genetically identical individuals in a given area.

• Building roads, houses, factories.

• Unsustainable harvesting e.g. over-hunting / over-fishing.

Define **Conservation**

Planned preservation of wildlife & habitats

Why is **conservation** vital?

It maintains biodiversity for the future

Define **SSSI** 

Sites of Special Scientific Interest

Define **CITES**

Convention on International Trade in Endangered Species of Wild Fauna and Flora

Define **whaling**

Whaling is hunting whales for their meat, oil, and other products

How can **conservation** be achieved?

• Habitat protection by nature reserves and SSSI (sites of special scientific interest) e.g. coral reefs.

• International cooperation between governments and organisations e.g. to restrict trade in animal parts such as ivory, or to ensure that the international trade in animal and plant specimens does not threaten their survival (CITES).

• Restricting activities that threaten an endangered species e.g. whaling

• Legislation to prevent overfishing, poaching, collecting birds' eggs, and picking wild flowers

• Breeding programmes by zoos and botanic gardens

• Sperm banks and seed stores

• Reintroduction programmes such as the Red Kite in Mid Wales

• Pollution control

What happens when **a gene pool is conserved**?

When a species is conserved, the gene pool of that species is also conserved

What is genetic diversity?

Genetic diversity refers to the variety of genes and alleles within a population or species

Why is genetic diversity **important?**

 Genetic diversity is critical if the species is to survive changing environments as natural selection is dependent on variation in the species.

How does conservation of gene pools benefit humans?

• some plants may be used for medicinal purposes

• Many of our crop plants have wild relatives that may contain useful genes that can be bred back into the crops

What is a **key dilemma** when it comes to conservation of species?

With an ever-increasing population to feed, there is a constant tension between the need to produce **more food** and the need to **conserve the environment and biodiversity**

Agriculture 

The means of producing food for human consumption in order to meet demand

How have **agriculturalists** tried to meet the growing demand for food?

• created larger fields by removing hedges

• cultivated monocultures (growing a single type of crop in a field)

• increased their use of fertilisers and pesticide.

How does **removing hedges** affect the environment?

**Hedges** provide valuable habitats for wildlife, including some pest species and their predators. They also provide “wildlife corridors” allowing mobile species to travel to different areas to disperse species and find mates

How does **cultivating monocultures** affect the environment?

**Monocultures** allow farmers to grow crops that are easy to harvest mechanically. They can also be guaranteed to yield disease-free seeds.

↳ However, if pest species invade a monoculture, they can increase in numbers very rapidly and a monoculture is less likely to sustain a variety of the pests’ predators which might keep their numbers under control

How does **using pesticides** affect the environment?

**Pesticides** harm beneficial species as well as pests and can cause them to decline in numbers.

How does **using fertilisers** affect the environment?

**Fertilisers** can cause eutrophication of nearby water bodies as any excess will leach into rivers.

What is **In-Situ Conservation?**

The conservation of a species in its natural habitat and the maintenance and recovery of viable population of species in their original place.

What is **Ex-Situ Conservation?**

Conservation outside of an organism’s habitat e.g. seed banks, or captive breeding programmes

What is **Deforestation?**

The **removal** of trees from an area to use the land for another purpose such as famring or building

How does **deforestation** cause desrtification?

Large areas of woodland are cleared and burnt using large machinery which compact the ground and necessitates road building. Succession is less likely to occur in these areas, leading to soil erosion. This means that tree seedlings cannot become established and the area becomes a desert

What are the effects of **deforestation?**

• Destruction of natural habitats and niches

• Decrease in native biodiversity

• Increase in soil erosion leads to an increase in nutrient loss

• succession from cleared land doesn’t occur because the top soil has been lost

• Increased sediment deposits in waterways

• loss of valuable plant materials which could have potential medicinal uses

• contributes to global warming (more carbon dioxide in the atmosphere because there are fewer trees to absorb it)

How can conservation reduce the effects of deforestation?

• Sustainable management means that timber can still be extracted without destroying the forest.

• Introduction of protected areas and replanting of native species within woodlands can also help preserve species and also promote biodiversity

Define **coppicing**

Woodland is divided into different areas to be cut down in rotation. Trees are cut to the stumps and the wood re-grows from the stump. The trees produce long straight stems which can be harvested.

What is **Overfishing**?

The level of fishing where **increased effort results in a declining catch**

Define **Fish farming** 

Isolating an area of sea for the purpose of breeding and growing fish in managed conditions. As with terrestrial farms, the animals are **fed**, **treated with chemicals** (to keep them pest and disease-free) and then **harvested**

How can the impact of overfishing be reduced?

• Fishing quotas – these limit how many members of any one species can be caught. Heavy fines are imposed for exceeding quotas.

• Reducing the size of fishing fleets - this means that fewer boats are out catching fish.

• Restricting seasons for fishing – by banning people from fishing during breeding seasons, the fish stock should have enough time to replenish.

• Restricting mesh sizes for fishing nets – smaller mesh sizes can catch more fish because they can catch both small and large fish. By having a minimum mesh size, larger fish will be caught but smaller fish, who are often juveniles, will be able to escape from the nets and go on to breed.

• Banning fishing from some zones (exclusion zones) altogether. In exclusion zones, the fish population will remain at sustainable levels

What are planetary boundaries?

the safe operating space for humanity

Why at happens if a threshold is exceeded?

There is the possibility of abrupt and irreversible environmental change.

Biosphere integrity

Exceeded

* biodiversity loss and extinctions. The main cause for this is increased demand for food, water and natural resources. Habitats are being lost rapidly, e.g. coral reef bleaching caused by ocean acidification and rising temperatures

Climate change

Exceeded

* This could push global temperatures and sea levels up. So too could the destruction of rainforest and weakened carbon sinks in tundra and oceans accelerate global warming

Chemical pollution and novel entities

Not yet quantified

* the emission of toxic and long-lived substances, such as heavy metals, radioactive materials and synthetic organic pollutants. These can cause reduced fertility and genetic damage, e.g. DDT dramatically reduced bird populations

Ozone depletion

Not Yet Exceeded

* The ozone has depleted in recent decades due to chemical pollution, e.g. CFCs from refrigerants and aerosols. Actions taken as a result of the Montreal Protocol, an international treaty signed in 1987, mean that this boundary has not been exceeded.

Aerosol loading

Not yet quantified

* aerosols are atmospheric pollutants. Their effects in the atmosphere are complex 

Ocean acidification

Avoidable

* This is owing to increased CO2 dissolving into oceans and forming carbonic acid. Organisms with calcium carbonate shells, like corals and molluscs can’t make shells in acid water. This has a knock-on effect on food chains and webs and could drastically reduce fish stocks

Land system change

Approaching Red

* this describes land converted to human use e.g. for agriculture

Freshwater consumption and the water cycle

Not yet Quantified

* globally fresh water is becoming scarce because of modification of water bodies and land use change. Desalination of sea water may ease the situation

Biochemical flows

• the nitrogen and phosphorous cycles

• Both elements are fixed into fertilisers but up-take by plants is limited leading to eutrophication. The production and application of fertilisers continues to be a concern