C1.6 Human impact on the environment

3 natural reasons for mass extinctions

severe high or low global temperatures, shortage of dissolved oxygen in oceans or ocean acidification

What is the cause of the 6th mass extinction?

Human activity

7 reasons species are threatened to extinction

natural selection, loss of habitat, overhunted for food or medicine, over-fishing, agricultural exploitation, competition from introduced species or pollution from oil and chemicals

4 Reasons we should conserve species 

Ethics, agriculture, environmental changes and potential medicine uses

What does conservation ensure?

Gene pools are conserved, meaning genes potentially useful for the species or humans aren’t lost 

Conservation strategies

Habitat protection, restricted trade, use of gene banks, species reintroduction, education, legislations and ecotourism 

3 reasons for deforestation

farming - grazing cattle or biofuel crops

timber - for fuel, building material or paper

building - roads or quarries 

consequences of deforestation:

________ CO2 in atmosphere

________ biodiversity 

________ water cycle 

________ humus
________ soil fertility

________ soil erosion

increased

decreased

disrupted

decrease

decrease

increase

4 issues with agriculture 

habitat loss
mono-cultures
maximising yields using chemicals

overgrazing 

examples of conservation strategies to limit agricultural exploitation

replanting hedgerows, allowing field margins, beetle banks, organic farming, legislation, grants and subsidies

Woodland management techniques

Coppicing - cutting trees near ground so new shoots can grow

Selective cutting - only felling largest trees, reducing soil erosion

Long rotation time - leaving parts of forest for decades to allow high biodiversity

Define overfishing

Fish are caught at a higher rate than they reproduce, leading to a decline in population

Strategies to reduce overfishing

Larger net mesh size to allow young fish to escape and reproduce

Laws and International agreements: Closed seasons, Fishing quotas, exclusion zones

Fish farming

What is fish farming?

Managed enclosures in lakes or rivers where fish are bred, matured and grown by adding high protein food, antibiotics and pesticides and protecting them with a net from predators

Environmental damage caused by fish farms

Antibiotic resistance, pesticides in aquatic food chains, eutrophication, farmed fish outcompete in local ecosystems, breeding can decrease genetic diversity and some is causing damage to habitats

What are planetary boundaries?

A framework of tipping points for 9 different factors that if crossed, it will result in abrupt and irreversible environmental change 

9 planetary boundaries 

Fresh water use, climate change, ozone depletion, biogeochemical flows, novel entities, land-system change, ocean acidification, atmospheric aerosols, and biodiversity integrity