Human Impact - created from Mind Map

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Extinction - Natural selection due to changing selection pressures ,Non-contiguous populations – populations which are too small with insufficient genetic diversity to ensure a healthy and viable increase in number , Loss of habitat e.g. deforestation, drainage of wetlands and loss of hedgerows ,Overhunting by humans (this includes overfishing) ,Competition from introduced (alien) species (interspecific competition) , Pollution due to human activity e.g. oil and PCBs

Conservation - Protecting habitats e.g. SSSIs and Nature Reserves  International co-operation restricting trade in endangered species and their parts e.g. ivory and the products of whaling (look at the CITES web site)  Gene & Sperm banks  Seed banks (Kew Gardens)  Rare breed societies  Species reintroduction e.g. the red kite in mid-Wales  International organisations which organise publicity to educate and increase public awareness e.g. WWFN  Legislation e.g. the EU Habitats Directive  Ecotourism, which aims to educate, conserve and contribute to local economies

Agricultural exploitation - Monoculture is the growth of large numbers of genetically identical crop plants in a defined area. Pesticides include chemicals which kill or inhibit the growth of weeds (herbicides), fungi (fungicides) and insects (insecticides). Chemical fertilisers include the elements NPK and increase plant growth.

Overgrazing land can cause soil compaction, reducing air spaces and inhibiting nitrogen fixing and nitrifying bacteria – leading to a loss of soil fertility (look back at Unit 3.5 on pages 39-43). Water is also unable to penetrate compacted soil and grass growth is inhibited.

Organic farming – reduces the need for chemical fertilisers and pesticides and allows for crop rotation on smaller fields. Different crops provide a variety of habitats and increase biodiversity.  Set-aside schemes – farmers manage their farms for biodiversity; land is set aside for conservation and wildlife. Government grants compensate the farmer for loss of income.  Legislation e.g. the Environment Act 1995 – loss of hedgerows has been reversed. Hedgerows provide habitats and food sources for insects, birds and small mammals. They provide nesting sites and act as corridors allowing wildlife to move from area to area safely.

Deforestation is the complete loss of trees (due to human activity) in a defined area. The land is then used for agriculture, building or infrastructure. Trees are being cut down faster than forests can regenerate. Consequences of deforestation include:  Soil erosion  Lowland flooding  Desertification  Habitat loss  Decrease in biodiversity  Climate change

 Coppicing – tree trunks are cut at their base, leaving a stool (stump) a few centimetres above the soil. New shoots grow from the stool which can be harvested at different diameters for different purposes e.g. building, fencing or fire wood. Coppiced woodland at different stages provides a variety of habitats and increases biodiversity.  Selective cutting  Long rotation time

Overfishing depletes fish stocks. Fish populations may become too low to recover – they are no longer viable. This also impacts food chains and entire ecosystems. Commercial fishing employs the following methods:  Drift netting – A net, suspended from floats, is stretched between two boats. Thousands of miles of nets are set and non-target species are often caught e.g. dolphins and turtles.  Trawling – Weighted nets are dragged across the ocean floor. This method catches everything and damages the ocean floor, decimating habitats for many miles. To preserve fish stocks the fishing industry is regulated by:  Regulating mesh size  Quotas and landing size regulations  Exclusion zones  Marine stewardship council certification  Legislation limiting the size of fishing fleets or controlling the number of days spent at sea  Fishing alternative, non-traditional, species  Using lines not nets

Fish farming is large-scale, intensive farming where fish are bred and mature in enclosed ponds. Food, predation, disease and parasites are controlled. Warm water is used to accelerate growth. Disadvantages of intensive fish farming include:  Rapid spread of disease and parasites due to the high density of the farmed population – this is controlled using antibiotics and pesticides and antibiotics which can enter the food chain. Pesticides bioaccumulate, causing a reduction in fertility at higher trophic levels.  Nitrogenous waste pollution leading to eutrophication and dissolved oxygen depletion.  The escape of farmed fish may carry disease and parasites to wild populations.  Farmed fish are larger and outcompete wild fish for resources should they escape.  Farmed fish, such as salmon, are fed on feed derived from other fish; this is a waste of resources.  Farmed fish, such as salmon, contain high levels of toxic chemicals such as methyl mercury, dioxins, pesticides and PCBs (pol

 Climate change boundary – Disruption of the carbon cycle due to burning fossil fuels, deforestation and increased decomposition. The release of carbon dioxide on a massive scale causes climate change due to enhanced global warming. See pages 39-40.  Biosphere integrity boundary (biodiversity boundary) – Human activity introduces new selection pressures which decrease biodiversity in relation to natural selection and increases the rate of extinction. See page 44.  The land use boundary – The balance between protection/conservation of habitats and human needs. Changes in farming practices, monoculture, the use of chemicals such as fertilisers and pesticides. See page 45.  The biogeochemical flows boundary (nitrogen boundary) – Disruption of the nitrogen cycle due to inhibition of nitrogen fixing and nitrifying bacteria and denitrification in waterlogged or compacted soils. Eutrophication due to nitrogen pollution in waterways. See pages 40-43.

The stratospheric ozone boundary – The only boundary avoided to date. In the stratosphere ultraviolet light causes CFCs to release chlorine as free radicals; free radicals break down ozone. The use of CFCs in aerosols and refrigeration has been reduced globally, reversing depletion of the ozone layer.  The ocean acidification boundary – The pH of the ocean is decreasing due to increasing atmospheric carbon dioxide concentrations. Carbon dioxide in the air dissolves in bodies of water as hydrogen carbonate releasing hydrogen ions; this causes acidification and a decrease in pH. Fish gills are damaged by low pH, calcium carbonate also leaches from mollusc shells and arthropod exoskeletons (crabs, shrimps and lobsters) – this causes softening making them more vulnerable to physical and chemical attack.  The fresh water boundary – All organisms need regular access to fresh water. Water sources include ice sheets, ice caps, glaciers, icebergs, ponds & lakes, rivers & streams and groundwa

The atmospheric aerosol boundary – Aerosols are microscopic particles released into the atmosphere by the combustion of fuels and by dust from digging, mining and quarrying. These particles can cause respiratory problems and reduce photosynthesis, as leaves are coated with particles cannot absorb as much light. Sulphates in aerosols reflect sunlight, providing some cooling effect, but other particulates, such as soot absorb sunlight and reradiate it.  The introduction of novel entities boundary – This was known as the chemical pollution boundary, but new technologies and materials release increasingly novel types of pollution. Organic pollutants, radioactive materials, nano-materials and plastics are included. Some chemicals are so toxic they have already been banned e.g. DDT and PCBs.