21. Human Influences on Ecosystems Flashcards
What has increased food supply?
Modern technology
In what 4 ways has modern technology helped increase food supply?
- agricultural machinery
- chemical fertilisers
- insecticides and herbicides
- selective breeding
How has agricultural machinery helped increase food supply?
Agricultural machinery has replaced humans and improved efficiency due to the ability to farm much larger areas of land
How have chemical fertilisers helped increase food supply?
Chemical fertilisers improve yields – fertilisers increase the amount of nutrients in the soil for plants, meaning that they can grow larger and produce more fruit
How have insecticides and herbicides helped increase food supply?
Insecticides and herbicides – these chemicals kill off unwanted insects and weed species, meaning that there is less damage done to plants and fruit lost to insects (insecticides), as well as reducing competition from other plant species (herbicides)
How has selective breeding helped increase food supply?
Selective breeding – animals and crop plants which produce a large yield are selectively bred to produce breeds that reliably produce high yields
What is monoculture?
Monoculture farming means that on a given area of agricultural land only one type of crop is grown (eg trees for palm oil grown in Indonesian rainforest)
What is a problem with monoculture relating to biodiversity?
This large scale growth of a single variety of plant does not happen naturally in ecosystems, where there are usually many different species of plants growing which, in turn, support many species of animals (high biodiversity)
In monocultures, biodiversity is much lower
What is a problem with monoculture relating to pests?
Another issue with monocultures is the increase in pest populations – if a particular pest feeds on a crop, farming it in large areas repeatedly means there is an ample supply of food for the pest, causing the population to increase
What is a problem with monoculture relating to insecticides?
Often farmers will spray insecticides onto crops in order to control the pests. This leads to:
harmless insects being killed as well
pollution by pesticides (which are often persistent chemicals which accumulate in food chains)
in many instances where they are used repeatedly for specific pests, the pests may eventually become resistant to them, reducing their effectiveness
What is a problem with farming livestock In developed countries?
In developed countries, large numbers of livestock are often kept in an area that would not normally be able to support more than a very small number
What are these livestock given which is harmful?
They are often
- fed high energy foods,
- regularly given medication such as antibiotics as a preventative measure against disease and
- kept in artificially warm temperatures and small spaces that do not allow for much movement
What are 3 ecological issues involved with intensive farming?
- reduction in biodiversity in areas where large amounts of land are used to graze cattle (as only grass is grown so in effect it becomes a monoculture)
- overgrazing can lead to soil erosion
- large numbers of cattle produce large amounts of methane, a greenhouse gas
When does a famine occur?
When people do not receive enough food, famine occurs
What can cause a famine? (4)
- natural disasters, such as drought and flooding,
- increasing population,
- poverty, and
- unequal food distribution
What has to happen to food production as population increases?
As the global human population increases, food production must also be increased to support the increasing population
Why is it bad that the food production industry has to keep increasing?
This is a problem as more land is required to grow crops and animals, meaning that deforestation is happening at an increasing rate, and there is also an increasing amount of greenhouse gases emitted from animal production
Why is an accumulation of greenhouse gases a problem?
Greenhouse gases cause global warming, which is a worldwide issue that leads to increased natural disasters, such as tropical storms and drought, as well as rising sea levels, which floods homes and decreases the amount of habitable land
What is the increasing human population doing in relation to habitats?
The increasing human population of the planet is causing destruction of many habitats from rainforest to woodland to marine
How can habitats be destroyed?
Many habitats are destroyed by humans to make space for other economic activities, or by pollution from these activities, and this reduces the biodiversity of these areas
Why is it harmful when habitats are destroyed?
This interrupts food chains and webs, meaning that more species may die because their prey is gone
What are the 3 main reasons for habitat destruction?
- clearing land for farming and housing
- extraction of natural resources
- marine pollution
How does clearing land for farming and housing contribute to habitat destruction?
- crops, livestock and homes all take up a large amount of space
- as there is an increasing population and demand for food, the amount of land available for these things must be increased by clearing habitats such as forests (deforestation)
How does extraction of natural resources contribute to habitat destruction?
- natural resources such as wood, stone and metals must be gathered to make different products.
- therefore many trees are cut down, destroying forest habitats. in addition, some resource extraction takes up a large amount of space
- for example: mining, which means that the land must be cleared first
How does marine pollution contribute to habitat destruction?
- human activities lead to the pollution of marine habitats
- in many places, oil spills and other waste pollutes the oceans, killing sea life
- in addition, eutrophication can occur when fertilisers from intensively farmed fields enters waterways
- this causes a huge decrease in biodiversity in these areas as most aquatic species living in these waterways die from lack of oxygen
What is deforestation?
Deforestation is the clearing of trees (usually on a large scale)
How can deforestation be a sustainable practice?
If trees are replaced by replanting it can be a sustainable practise
Why does deforestation usually occur?
Generally the trees are being cleared for the land to be used in a different way (for building, grazing for cattle, planting of monocultures such as palm oil plantations etc) and therefore it is not sustainable
What is a particularly severe example of habitat destruction?
As the amount of the Earth’s surface covered by trees decreases, it causes increasingly negative effects on the environment and is a particularly severe example of habitat destruction
What are 4 undesirable effects of deforestation?
Undesirable effects of deforestation include:
Extinction of species
Loss of soil
Flooding
Increase of carbon dioxide in the atmosphere
How is extinction of species an undesirable effect of deforestation?
- forest habitats, especially tropical rainforest s, have a huge range of biodiversity and as habitat is destroyed it causes the loss of large numbers of plant and animal species
- many of these species are only found in these areas therefore will become extinct
How is loss of soil an undesirable effect of deforestation?
- tree roots help to stabilise the soil, preventing it from being eroded by rain
- trees will usually take up nutrients and minerals from the soil through their roots
- without trees, nutrients and minerals will remain unused in the soil so will be washed away into rivers and lakes by rain (leaching)
- this loss of soil nutrients is permanent and makes it very difficult for forest trees to regrow, even if the land is not cultivated with crop plants or grass for cattle
How is flooding an undesirable effect of deforestation?
- without trees the topsoil will be loose and unstable so will be easily washed away by rain, increasing the risk of flash flooding and landslides
How is increase of carbon dioxide in the atmosphere an undesirable effect of deforestation?
- trees carry out photosynthesis during which they take in carbon dioxide and release oxygen
- the removal of significant numbers of trees means less carbon dioxide is being removed from the atmosphere (and less oxygen released)
- when areas of land in forests are cleared for land use, the trees are of ten burned as opposed to being cut down. this releases carbon dioxide (it is an example of combustion), further increasing carbon dioxide levels in the atmosphere and contributing to global warming
What types of pollution have human activities caused?
Human activities have led to the pollution of land, water and air
What sources can pollution come from?
- industry and manufacturing processes,
- waste and discarded rubbish, - chemicals from farming practices,
- nuclear fall-out,
- untreated sewage
What is the source/cause for untreated sewage?
lack of sewage treatment plants in inhabited areas due to poor infrastructure lack of money meaning sewage runs / is pumped into streams or rivers
What is the source/cause for chemical waste?
chemicals such as heavy metals ike mercury can be released from factories into rivers and oceans or leach into land surrounding the factories
What is the source/cause for discarded rubbish?
much rubbish consists of plastic that is either discarded or buried in landfills
What is the source/cause for fertilisers?
runoff from agricultural land applied in too high concentration
What is the source/cause for insecticides and herbicides?
sprayed on crops to prevent damage by insects and growth of weeds
What is the source/cause for nuclear fallout?
radioactive particles that get into the environment from accidental leakage from nuclear power plants or explosion of a nuclear bomb
What is the source/cause for methane?
cattle farming, rice fields, landfills
What is the source/cause for carbon dioxide?
produced when fossil fuels are burnt, also released when trees are burnt to clear land for human use
What is the effect of untreated sewage on the environment?
provides a good source of food for bacteria which increase rapidly, depleting the oxygen dissolved in the water (as they respire aerobically) and causes death of aquatic organisms such as fish- known as eutrophication
What is the effect of chemical waste on the environment?
many heavy metals and other chemicals are persistent- they do not break down and so can build up in food chains (known as bioaccumulation), poisoning the top carnivores
What is the effect of discarded rubbish on the environment?
much rubbish, such as that made from plastic, is non-biodegradable and remains in the environment for hundreds of years. animals also eat the plastic as it breaks into smaller pieces (especially in the ocean) and it can get into food chains this way
What is the effect of fertilisers on the environment?
causes algal blooms which then die and provide a good source of food for decomposing bacteria which increase rapidly, depleting the oxygen dissolved in the water as they respire aerobically) and causing death of aquatic organisms such as fish known as eutrophication
What is the effect of insecticides and herbicides on the environment?
bioaccumulation, loss of biodiversity, damage to beneficial insects. can build up in soil to toxic concentrations and harm other organisms
What is the effect of nuclear fallout on the environment?
some radioactive particles have long half-lives and can remain in the environment for many years. they can cause increased risks of cancer and smaller particles can be carried by winds hundreds of miles from the original site of exposure
What is the effect of methane on the environment?
methane is a greenhouse gas which contributes to the enhanced greenhouse effect that is causing climate change
What is the effect of carbon dioxide on the environment?
carbon dioxide is a greenhouse gas which contributes to the enhanced greenhouse effect that is causing climate change
Why do plastics have such a negative impact on the environment?
Plastics have a large negative impact on both land and water habitats due to their non-biodegradability
- What effects does plastic have on animals in marine habitats?
- Animals often try to eat plastic or become caught in it, leading to injuries and death
