Summary
Summary Unit 3.6 - Human Impact of the environent
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- WJEC
Notes on extinction, deforestation, bioaccumulation, conservation methods, agriculture, aquaculture, overfishing, sustainability and planetary boundaries
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3.6 Human impact on the environmentExtinction:
Humans are causing massive destruction of habitats through:
o Agriculture
o Urban development
o Forestry
o Mining
o Environmental pollution
Led to a biodiversity crisis because we’ve deprived species of biotic and abiotic factors they need
for survival leading to less successful reproduction, population decrease and sometimes
extinction
Endangered = at risk of extinction
Habitat destruction -> biodiversity crisis -> less reproduction -> smaller population -> extinction
Some causes of extinction are: new predators, new disease, natural disasters, climate change,
habitat destruction, pollution, natural selection, hunting
Extinction is a natural process but the rate is shocking (normal rate is one in a million species per
year. Due to human influence, it’s between 1000 and 10,000 times greater than that)
Sixth mass extinction seems to be underway caused by humans
Humans are responsible extinction of several megafauna such as Moa
Bioaccumulation:
Bioaccumulation = gradual build up over time of a chemical in a living organism
These chemicals are passed up the food chain to each trophic level and become more
concentrated as they do animals at the top of the food chain are affected the most severely
Small amounts of toxic substances are taken up by producers
Plants are eaten by primary consumers
Eaten by secondary consumers etc
Toxins remain in tissues of organisms so toxin conc is highest in animals at top of the food chain
PCBs are a toxic product of some industrial processes and used in paints, plastics and electronics
They can leach out of landfill sites into waterways & gradually increase in conc up the food chain
PCBs were banned in UK 30 years ago but lingering affect has affected reproductive success of
Orcas
Some critically endangered species are black rhino, bog turtles and Asian elephants
Conservation:
Conservation = protection, preservation and management of natural habitats and their
ecological communities to enhance biodiversity whilst allowing for sustainable human activity
Conservation has to be addressed at local, national and international levels
Insitu = conserved in natural habitat e.g. national parks, wildlife reserves
Exsitu = conserved elsewhere e.g. zoos, seed banks
Methods of conservation:
o Creating sites of special scientific interest of national parks
o Making laws to protect species and control trade
, o Captive breeding programmes
o Genetic banks
o Species reintroduction
o Education
o Ecotourism
CITES –Convention of international trade of endangered species
It is an international agreement between governments which aims to ensure that international
trade in specimens of wild animals and plants does not threaten the survival of the species
Laws help by:
o Preventing overgrazing
o Preventing overfishing
o Supporting endangered species
o Prevent hunting of animals and birds
o Reduce collecting of eggs
o Reduce collecting of flowers
Captive breeding programmes are normally carried out in zoos, parks or gardens where
endangered species are helped to breed successfully and try and build up a healthy population
number. It’s often done across several countries and zoos to increase the gene pool
Genetic banks’ purpose is to store genetic material for the future e.g. seed banks store seeds to
preserve genetic diversity. Stores traditional and vulnerable species in highly controlled
conditions. E.g. Seed banks store genes of economically important animals and threatened
species for breeding programmes.
Reintroduction can help species recover from the brink of extinction e.g. Red Kite
Education – global organisations like WWF do public awareness campaigns. Also, school and
university curriculums can influence awareness
Ecotourism recognises that mass travel is harmful so aims to:
o Contribute to conservation efforts
o Employ locals and give back to local communities
o Educate visitors about local environment and culture
o Cooperate with local people to manage natural areas
Gene pools are very important in conserving a species. Conserving genes needs to be done in
the wild and in captivity
Why conserve gene pools?
o Ethical reasons – each unique species has intrinsic value
o Agriculture/horticulture - prevent loss of rare alleles in crops that are beneficial for
hardiness and disease resistance
o Medical uses – Yet to discover all medicinal drugs out there e.g. quinine treats malaria
Agricultural exploitation:
Agricultural exploitation = conflict between food production and maintaining habitats and
species diversity
Monoculture = large fields grow single crops with no diversity of different microhabitats –
supports less organisms
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