3.6 Human impact on the environment

Define endangered.

Species at risk of extinction due to small numbers left, often as a result of human activity.

Define extinction.

No more individuals of that species alive in the world.

Why is extinction currently a problem?

The speed it is occurring in the anthropocene with an increase in the tropics, due to global warming.

Why does coral bleaching occur?

Zooxanthelle that is photosynthetic and nourishes soil, and is expelled from coral under stress of the high temperatures.

An example where humans have caused extinction.

Passenger pigeon: game pigeons caused a genetic bottleneck as genetic diversity rapidly decreased overtime and so interbreeding occurred. Population for millions to extinct within 50 years.

How many mass extinctions have occurred?

5 mass extinctions due to catastrophic events in the past.

3 reasons for mass extinction events

1. Low global temperatures e.g. ice age

2. Shortage of dissolved oxygen

3. Acidification of oceans (volcanic eruptions)

Define conservation.

The protection, preservation, management and restoration of natural habitats and their ecological communities.

What is the aim of conservation?

To maintain species and genetic diversity, while allowing human activity to continue.

List the 9 main conservation methods.

1. Ecotourism

2. Protecting habitats

3. International cooperation

4. Gene and sperm banks

5. Seed banks

6. Rare breed societies

7. Species reintroduction

8. International organisations

9. Legislation

Explain and give example for the following conservation methods:

1. Ecotourism

2. Protecting habitats

3. International cooperation

4. Gene and sperm banks

5. Seed banks

6. Rare breed societies

7. Species reintroduction

8. International organisations

9. Legislation

1. Aims to educate, conserve and contribute to local economies e.g. Galapagos Islands

2. Ensures biodiversity maintained and prevents species loss e.g. SSSIs and nature reserves.

3. Restricting trade of endangered animals and their parts e.g. elephants and ivory.

4. Stores genetic material to prevent extinction e.g. London

5. Stores seeds in dry, cold conditions to prevent extinction e.g. Kew Gardens

6. Organisations protecting at risk breeds e.g. Rare Breeds Survival Trust (RBST)

7. Deliberate reintroduction of species to natural area where it was once lost to restore ecosystem e.g. Red Kite in mid-Wales

8. Organise publicity to educate and increase public awareness e.g. WWF

9. Laws to protect threatened animals e.g. EU habitats directive.

3 reasons for vitality of conservation.

1. Species and genetic biodiversity protection is essential for new crops for agriculture and new pharmaceuticals for medicine.

2. Diversity of alleles essential to combat climate change as some will have a competitive advantage to prevent extinction.

3. Ethical issue with the sanctity of life.

Conversion of one hectare to m² to m.

1 hectare = 100m² = 10,000m

2 main reasons that world population has increased.

1. Post world war 2 baby boom (1900s)

2. Industrial Revolution (1800s) where machinery and technology like combine harvesters were implemented to farms. More food to support more people.

What does farmland create (type of environment)? What is the problem with this?

Monoculture where 1 crop is grown on repeat and reduces biodiversity significantly. Yield decreases year after year as roots are the same depth and length, so nutrients rapidly decreases (farmers need to spray NPK). Disease and pest rapidly spreads

Method farmers should use to reduce problems with monocultures.

Rotate crops.

Define deforestation.

Removal of forest space by cutting down trees, by humans, at a faster rate than they are grown.

5 main problems of deforestation

1. Less CO₂ removed, as trees are carbon sinks, so adds to climate change as atmospheric CO₂ increases.

2. Removes habitats

3. Combustion releases CO₂ e.g. as fuel

4. Overgrazing by cattle on clear land which compacts the soil and so makes it less permeable to water, resulting in flooding.

5. Reduced biodiversity and habitats as a result of all of the above

Define soil erosion.

The removal of topsoil which contains valuable nutrients.

What is the old method of forest management?

Slash and burn where small area of forest removed for crops, then area is burnt to allow ash to settle. This makes the soil more fertile, so land recovers.

Why is slash and burn no longer effective?

Can only occur annually and on a very small local scale.

How does coppicing manage forests and describe?

Cut the trunks and leave a few centimetres for new shoots and bunds to grow into poles for timber. It is a sustainable method.

Consequences of removing trees on steep slopes? (2)

1. Never remove trees on top of slope as it causes lowland flooding as trees slow rainfall. Roots also stabilise soil, so removal is loss of topsoil (most minerals and nutrients), leading to a blowout.

2. Trees removed so the leaf and humus layer that acted like a sponge is removed. This leads to waterlogged soil, promotes anaerobic bacteria (denitrifying) and is cold, preventing germination in the spring.

Management of forest on steep slopes?

1. Keep trees at top of slope

2. Ensure certain distances between trees are kept to bind the soil. When optimum distance obeyed, there is less infraspecific competition.

3. Quota of trees that can be cut down per time period (selective cutting).

Is evaporation or transpiration slower, so what does this mean?

Evaporation slower, so water removed less from soil.

How does overfishing often occur?

Large trawlers and fishing nets along with radar technology has caused fishing stocks to decline. A balance needs to be struck between maintaining jobs and overfishing.

3 main issues with large trawling nets.

1. Net sizes crucial to sustainability of a fish population.

2. Small net sizes are needed to prevent catching fish before they reach sexual maturity.

3. If sexually mature fish are caught then there are less to breed and the population will decline.

4 issues with commercial fishing?

1. Drift netting - pelagic (deep or ocean sea) fish can live in the surface waters and get caught in the nets.

2. Nets can be miles long and are usually suspended between boats, so other species are caught, which are also killed and not eaten.

3. Trawling - fish that live in deeper water and also those who are bottom or mid-water feeders can get trapped by this method.

4. Large nets get dragged along and trap whatever swims in. Frequency = damages ocean floor and destroys habitats for molluscs and so populations endangered.

Why are fish farms used?

Farms provide optimum food supplies and reduced predation e.g. UK farms salmon and trout.

What are added to fish farms and what encourages faster growth?

Artificial fertilisers added to encourage plankton growth for artificial plankton feeders.

Warm waters encourage faster growth - industrial effluents

3 reasons fish farms are better than meat?

1. Fish are more efficient at converting their food into protein compared with pork/poultry/beef.

2. More of the fish body is edible compared with other species.

3. Fish farming has a lower carbon footprint than rearing other animal species.

5 main fish farm problems

1. Diseased fish due to density of stocks. Antibiotics need to be used, but these affect invertebrates e.g. molluscs.

2. Pollution eutrophication may result from fish excreta/waste food and fertiliser.

3. Resource use as farmed salmon eat far more than wild salmon = poor use of resources from an environmental point of view.

4. Environmental toxins - PCBs, methyl mercury, dioxins, pesticides are more concentrated than wild salmon BUT their concentrations are too high to cause harm to humans.

5. Environmental degradation - fish farms e.g. shrimp have been blamed for salinisation of soil and ground water and so damage to mangrove swamps which would normally protect coastal communities against tropical storms.

9 planetary boundaries

1. Climate change

2. Biosphere integrity

3. Land-system change

4. Biogeochemical flows

5. Ozone depletion

6. Ocean Acidification

7. Fresh water use

8. Atmospheric aerosol loading

9. Introduction of novel entities

Define planetary boundaries.

Limits between which global systems must operate to prevent abrupt and irreversible environmental change.

Define core boundary and what are they?

Crossing this planetary boundary would drive the Earth into a new and unpredictable state with severe consequences for the biosphere. They are climate change and biosphere integrity.

Describe the climate change boundary.

One of the two core boundaries, and has been crossed. It is the safe operating level for climate change for humans, often caused by greenhouse gases released from combustion.

What is biofuels and why was it developed?

A fuel made by biological process such as anaerobic digestion, rather than geological (fossil fuels), and developed to contribute to reduction in fossil fuel combustion, to help climate change boundary.

5 concerns with biofuel production.

1. Food vs Fuel debate: land that could be used for food is being used for crops for fuel e.g. palm oil (monocultures)

2. Sustainable biofuel production relies on sustainable planting and efficient technical systems.

3. Deforestation to grow biofuel crops leads to soil erosion and BD loss.

4. Reduction in water availability, because biofiuel crops require a large volume of irrigation water.

5. Combustion of biodiesel produces more nitrous oxide (NO₂), a greenhouse gas, than fossil fuel.

Petrodiesel vs biodiesel.

Diesel made from fosisl fuels is called petrodiesel.

What is the biosphere integrity boundary? How to rectify?

Loss of genetic and functional diversity with habitat destruction and pollution causing extinctions. Monitoring BD is imperative to prioritise species to put in gene banks. Increase public awareness.

What is the land system change boundary? How to improve?

Amount of land used in terrestrial biomes, e.g. deforestation has occurred. Farming should be concentrated into the most productive areas and a global reduction in meat consumption would decrease cattle land use.

4 reasons for land use change

1. Livestock

2. Cash crops

3. Biofuel crops

4. Urban development

What is the biogeochemical flow boundary?

The cycling of minerals through biotic and abiotic components of an ecosystem e.g. fertilisers disrupt the nitrogen cycle.

What is the ozone depletion boundary?

Ozone and oxygen are normally in equilibrium, but CFCs (halogenated hydrocarbons) alter equilibrium to favour breakdown of ozone, due to Cl free radicals being made.

How was the ozone depletion boundary stopped from being crossed?

International agreements (Montreal Protocol) that banned CFCs in spray cans.

What is the ocean acidification boundary?

The pH of the oceans has become more acidic, small change is actually greater as pH is logarithmic. Carbon dioxide from air dissolves to hydrogen carbonate which releases H⁺ ions when dissolved in water.

Why is ocean acidification such a problem for aquatic ecosystems?

pH leaches calcium carbonate out of mollusc and coral shells and athropod exoskeletons, softening them so vulnerable to physical and chemical attack.

How to prevent the crossing of the ocean acidification boundary?

Probably avoidable as it has not yet been crossed, but a reduction of fossil fuel combustion may prevent catastrophic pH change.

Define fresh water?

Fresh water has low concentration of dissolved salts, i.e. <0.05%.

What is the fresh water boundary?

Below this boundary organisms do not have enough fresh water to survive, as 97% of all water on Earth is saline,

7 reasons why fresh water availability has decreased.

1. Changing landscapes

2. Agriculture consumes lots of water

3. Increased demand in warm climates

4. Water pollution (e.g. eutrophication)

5. Climate change - glaciers melt, thermal expansion of water, relying on rainwater for supply

6. Increase in population by increased life expectancy

7. Increase in use

6 methods for increasing availability of fresh water

1. Water conservation (non-food crops shouldn’t be irrigated)

2. Water efficiency

3. Wastewater reclamation for irrigation and industrial use

4. Urban run off and storm water capture, recharging groundwater

5. Drip irrigation systems reduce water used

6. Desalination

2 methods of desalination

1. Solar stills distil seawater with heat from sun. No pollution and saltwater is entirely converted into distilled water.

2. Reverse osmosis: fine, selectively permeable membrane. Requires energy, but sensible method as waste heat of nuclear plants used generate steam to drive desalination.

3 environmental problems from desalination.

1. Brine (conc sodium chloride) is discharged: must be diluted before returned to oceans

2. Brine denser than seawater and sinks and damages seabed ecosystems.

3. Burning of fossil fuels to generate heat to run the system

3 aspects to fresh water supply

Quality, volume and timing where a change in one often leads to change in the others.

What is the atmospheric aerosol loading boundary?

Microscopic particles put into atmosphere by their combustion of fuels by creating dust from digging and quarrying.

3 main problems of aerosol loading?

1. Exacerbate respiratory problems

2. Deposition of leaves reduces photosynthesis and so crop yields reduced.

3. Sulphates in aerosols reflect sunlight, with a cooling effect.

What is the introduction of novel entities boundary?

Increasing use of new technologies and materials with organic pollutants, radioactive materials, nano materials and microplastics.

Which 2 boundaries are most avoidable?

Fresh Water and Ocean acidification

What 2 boundaries have not been quantified?

Aerosol and novel entities boundaries, but novel entities still deemed to be safe.