3.6 - Human impact on the environment Flashcards
Why species are at risk?
the influence of humans have spread to every landmass on earth.
Human activities are altering ecosystems upon which they and other species depend.
Massive destruction of habitats throughout the world has been brought by agriculture, urban development, deforestation, mining and environmental pollution
Extinction ?
natural process that has been taking place since life originated.
What does fossil record showing the normal background rate of extinction being 10^-6 y^-1 mean?
means that each year, one species in a million becomes extinct
Extinction examples?
death of megafauna
large animals such as the moa
giant ground soluth from south america
extinction of the passenger pigeon in north America.
1914 - thylacine from tasmania
1936 - exposure to humans
1/3 of planet’s marine fish species on coral reefs
some data suggest that at the current rate of destruction, all warm water coral reefs could have died by 2050.
Geological evidence shows?
5 times in the history of life, the vast majority of species have been made extinct by a catastrophic change, such as low global temp, shortage of dissolved oxygen in the oceans or ocean acidification.
Described as mass extinctions
Endangered species?
vast majority of Earth’s earlier occupants, including the large and once dominant dinosaurs and tree ferns have become extinct largely as a result of climatic, geological and biotic changes
At present time, human activity has taken over as the main cause of species extinction
many of larger mammals such as mountain gorillas, giant pandas, tigers and polar bears = threatened
What organisations make assessments of plants and animals and grades them according to their vulnerability to extinction?
IUCN
the international union for conservative of nature
How are species rated?
depending on their numbers, rate of decline and distribution
EX?
extinct
EW?
extinct in the wild
Threatened
CR?
critically endangered
EN?
endangered
VU?
vulnerable
NT?
near threatened
LC?
least concern
DD?
data deficient
NE?
not evaluated
African elephant?
vulnerable
Sumatran elephant?
critically endangered
Why are species endangered or extinct?
Natural selection
Non contiguous populations
Loss of habitat
Overhunting by humans
Competition from introduced species
Pollution
Natural selection?
occurs when individuals = less suited to prevailing conditions reproduce less successfully
numbers decrease which may lead to their extinction
Human activities are causing habitats to change faster than new mutations allow species to adapt and so they are driven to extinction at a faster rate than before humans had such influence over their environment
Non contiguous populations?
total number of individuals in a species may suggest that numbers are sufficient to ensure the continuation of the species.
If groups are isolated from each other?
they cannot interbreed and each group functions as a separate population
may be too little genetic diversity in each to ensure a healthy population leading to their extinction.
e.g black rhinos in africa
Loss of habitat?
Deforestation
Drainage of wetlands
Hedgerow loss.
e.g Hedgerows have separated fields for centuries.
Provide a habitat for insects, nesting sites for birds + reptiles, food for many species and varying light intensity and water availability for diverse plants
What do hedges act as?
wildlife corridors enabling reptiles, birds and mammals to move from one area to another, helping to maintain biodiversity.
Their removal, often to accommodate the large agricultural machinery used in modern farming has destroyed large areas of this specialised habitat
Herbivores and other consumers reduce in numbers with consequent reduction at higher trophic levels.
Why do farmers sow crops in autumn rather than spring?
plants are an unsuitable height for the birds to build their nest
led to a decrease of well known birds such as skylark and lapwing
What does overhunting include?
Trophy Hunting - countries that allow this charge for privilege and claim old or sick animals are hunted
Some traditional medical practices e.g use of tiger body parts, pangolian scales and rhino horn
Bush meat industry - primates and others are killed for food
Overfishing
Agricultural exploitation
Competition from Introduced species?
Dodo - was driven to extinction because rats were brought on european ships, ate the dodo eggs
North American signal crayfish has invaded UK streams and rivers and the native crayfish which is smaller, is being outcompeted
Red squirrels - have declined due to habitat loss and in many places, are being outcompeted by the north american grey squirrel
Pollution?
Oil is shipped worldwide in supertankers, some of which = to big ever to enter a port.
Therefore, accidental discharge of oil into the sea occurs for example
Torey canyon disaster between Cornwall and isles of Sicily in 1967
exon valdez disaster off coast of Alaska in 1989 : largest petrol spill in fresh water was from a royal dutch tank ship. estrella near the coast of Argentina.
Polluted the environment, contaminated drinking water and killed plants and animals
Why is oil harmful?
prevents oxygenation of surface water.
Animals break through the surface are covered by a film of oil.
Birds, subsequently are chilled to death because their feathers are clumped together and cannot provide insulation.
Oil is washed up on beaches is ingested by shore dwelling animals which are poisoned by it
PCBS?
polychlorinated biphenyls.
Artificial substances which have accumulated in the food chain and so are ingested in some foods containing animal products.
Neurotoxins, carcinogens and hormone disruptions, their use was progressively banned in the UK between 1981 and 2000
Conservation?
the protection, preservation, management, restoration of natural habitats and their ecological communities to enhance biodiversity while allowing for suitable human activity
Examples of conservation
Protecting habitats
International co operation
Gene banks
Education
Legislation
Ecotourism
Protecting habitats?
protects the species that live there and communities act as living gene banks.
Official designation recognises local nature reserves, sometimes as small as a few hectares.
Larger, national nature reserves such as the Gower Coast, SAC’S,
( Special areas of conservation)
SSSI
( sites of special scientific interest)such as the brecon bog and other sites.
Have varying levels of legal protection and may be managed and monitored by wardens.
International cooperation?
restricting trade in ivory and whaling.
International law allows some countries to practise scientific whaling but many consider the term scientific to be disingenuous and there are organised attempts to stop it from happening
Gene banks?
Endangered species are protected and entered into breeding programmes in specalised zoos and botanic gardens.
Pandas are held in great affection and attempts by zoos to persuade them to breed
Records of matings ate kept so geentic diversity can be increasesd by deliberate choice of parents.
Sperm banks?
used to store genes of economically important animals and of threatened species.
Rather than moving animals, sperm samples can be sent arounf the world to use in breeding programmes in other zoos.
Seed banks?
maintain stocks of seeds of traditional varieties and of vulnerable species in highly controlled conditions, liquid nitrogen.
Although plant fro a 2000 year old judean date palm seed has successfully grown, seeds degrade over time.
So periodically, samples are thawed and germinated.
Seed banks in some countries have very high levels of protection as they are viewed as a potential source of food in case of catastrophic environmental degradation
What do rare breed societies maintain?
older, less commercial varieties for special characteristics, e.g hardiness and wool production
Species reintroduction?
Red kite in mid-wales
the chough in cornwall, the Arabian oryx in Israel and Jordan, the giant condor in California and the Przewalski horse in Mongolia have all been driven to the brink of extinction.
Following successful breeding programmes have been reintroduced to their former habitats
Education?
Global organisations such as he World Wide Fund for nature, mount public awareness campaigns/
Natural resources wales is a government body promoting nature conservation.
It advises government and groups whose activities affect wildlife and their habitats
It produces publications, proposes ecosystem management of schemes and establishes nature reserves.
Legilsation?
The EU habitats directive has imposed a range of measures to protect habitats and enhance biodiversity throughout Europe, preventing overglazing, overfishing,hunting of game, collection of birds eggs, picking of wild flowers and plant collecting
Ecotourism def?
Responsible travel to natural areas that conserves the environment and improves the well-being of local people
What does ecotourism recognise?
that mass travel is harmful globally and to specific habitats.
It aims to:
Contribute to conservation efforts
Employ local people and give money back to local communities
Educate visitors about local environment and culture
Cooperate with local people to manage natural areas.
Why conserve?
Ethical reasons
Agriculture
Potential medical uses
Ethical reasons?
each species represents a particular combination of genes and alleles adapted to a particular environment and ir is considered that the uniqueness of each is intrinsically valuable
Agriculture + Horticulture?
plants + animals used in agriculture and horticulture have been developed from those in the wild.
Selective breeding increases genetic uniformity, with the loss of rarer alleles.
In the past, breeders may have neglected some important qualities such as resistance to cold or disease.
They need to be bred back into cultivated varieties, using the wild plants and animals as a gene bank.
If habitats and the wildlife that live in them are threatened, it may no longer be possible.
What happens if the environment changes?
some alleles will provide an advantage to the individuals that carry them and those individuals will be selected for, preventing the extinction of that species
Potential medical uses?
Antibiotics we use are derived largely from fungi but may other of our medicinal drugs are synthesised by plants.
e.g quinine - extracted from the bark of cinchona, an amazon rainforest tree used to treat malaria.
Why is agriculture essential?
to produce the quantitiy and quality of food required to feed the increasing human population.
Environmental implications examples?
many hedgerows were removed to make larger fields to enable machinery to prepare the soil and harvest crops
Larger fields = used for monoculture, where single crops breeds or varieties e.g wheat or barley are grown over a large area.
With mixed crops, there are many different microhabitats and so many different plants and therefore, many different animals could live there.
Monoculture def?
the agricultural practice of growing of a single crop, breed or variety over a large area
What happens if the same crop is grown on the same plot year after year?
Yield progressively declines because:
The root are always the same length, so they extract the same minerals from the depth of the soil.
Intensive cultivation has therefore hugely increases the use of inorganic fertilisers
Same crop = always susceptible to same pests, which increase in number, so more intesticides, herbicides and fungicides are used.
What does overgrazing do?
causes grassland to become unsuitable
Their hooves compact the sil, driving out the air, preventing water from draining through.
Roots cannot penetrate the soil and so grass for grazing cannot grow.
Deforestation?
Widespread because timber is used extensively both as a building material and as fuel, as well as providing paper and packaging.
Land is also cleared for farming, often to produce biofuels or grazing for the cattle destined for the meat industry.
Specific high value trees, such as teak or mahogany may be targeted and felling and removing them damages many others in the process.
Consequences of Deforestation?
soil erosion
Deforestation of uplands causes lowland flooding
Soil erosion def?
the removal of topsoil which contains valuable nutrients
Soil erosion?
roots bind soil together.
Deforestation on the higher slopes of valleys allow heavy rain to sweep exposed topsoil down to the flood plains below.
Topsoil?
fertile soil and what remains is not suitable for crop growth
Under normal conditions?
on the lower slopes, plant, humus and leaf litter act as a sponge, soaking up heavy rainfall and water is only gradually released into the soil.
Trees transpire and return water to the atmosphere.
After deforestation?
there are no plants and water evaporates from the soil.
Diminishing the quality of the soil.
Evaporation?
returns water vapour to the atmosphere more slowly than transpiration so soil on deforested land becomes water.
Water fills the soil’s airspaces and so the oxygen available for roots decreases.
It takes longer for a wet soil to warm up than a dry soil, so these soils are also cold.
Germination and root activity are reduced.
Cold, damp soil favours the growth of denitrifying bacteria and so soil loses its nitrates and therefore fertility.
Less rainfall?
water only returns to the atmosphere by evaporation from the spil, not by transpiration and evaporation is slow.
Accelerates desertification.
Habitat loss and reduction in biodiversity?
estimated that 50 % of the Earth’s species live in the tropical rainforests, which cover only about 10 % of the Earth’s land area.
Destruction of such natural habitats may lead to the loss of some tropical species.
They may become extinct before their clinical properties have been investigated. Estimated that every day, rainforest deforestation makes 25 plant and animal species extinct.
Effects on the atmosphere?
as photosynthesising trees are cut down, the removal of CO2 from the atmosphere by photosynthesis is decreased.
Cut trees may be burned, or left to decay, releasing CO2 in the atmosphere.
Slash and burn meaning?
small forest is cut and burned.
People grow crops on soil fertilised with ash from the burned trees.
When soil = no longer fertile, people leave and are regenerates.
Sustainable on a small scale but not a large scale
