Chapter #19 - Human Influences On The Enviornment Flashcards
How has food production changed over time?
In the past few hundred years, food production has greatly increased. Of course, we must increase food production to feed our growing population.
Why has food production increased?
- Agricultural machinery
- Agricultural chemicals
- Selective breeding
- Monocultures
How has agricultural machienery increased food production?
Development of machinery like tractors and combine harvesters allow farmers to cultivate a larger area of land in a smaller amount of time.
What are the different types of agricultural chemiclas?
- Chemical fertilisers
- Insecticides
- Herbicides
Why would agricultural chemiclas be used?
Farmers use chemicals to improve crop growth, to get more yield from the same area of ground.
How do chemical fertilisers increase food production?
add more mineral ions (eg. Nitrate) to soils
How do insecticides increase food production?
are sprayed onto crops to kill insect pests that may reduce yields or make the crop look less appealing to buyers.
How do herbicides increase food production?
are sprayed to kill weeds, which compete with crops for space and therefore limit their growth.
Why does selective breeding
- Farmers carefully select plants and animals to create new varieties which produce greater yields.
- E.g. Modern wheat varieties produce far more grain per plant than older ones did.
- Selective breeding has produced plants that can grow in poor soils, or are resistant to disease.
- Cattle now produce more meat / milk than they did in the past
- Hens lay more eggs
Monoculture
an area of ground covered by a single crop, with almost no other species present. (often used in developed countries)
What are the advantages of monocultute?
- They make sowing, tending, harvesting and sellingmore efficientfor the farmer because:
- Using machinery to tend to a large area of land is faster & more efficient than tending multiple small separate fields.
- A uniform crop is more likely to grow to the same height and ripen at the same time (can be harvested all at once with machinery).
- A large monoculturecan be treated with the same herbicides/pesticides in the same way at the same time.
- A monoculture will producelarge quantities of seeds, fruit, etc. that are all similar in size and quality = easier to sell.
What are the main disadvantages of monocultures?
- Reduction of biodiversity (the number of different species that live in an area)
- Increase in pests that thrive on large supply of food.
- Reduction in soil fertility
How is reduction of biodiversity a disadvantage of monoculture?
Only a few species can live where the crop is growing. In natural ecosystems, there are usually manydifferent species (high biodiversity).
How is an increase in pests a disadvantage of monoculture?
- Increase in pests that thrive on large supply of food.
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E.g. Leafhoppers feed on rice plants (reducing yields).
-They alsotransfer plant viruses to the rice – spreading disease.
-If a large areahas onlyrice plants,the leafhopper population will thrive.
-Farmers can use pesticides, but this is expensive and kills other insects which are not threats (including those that prey on leafhoppers!)
In many places, leafhoppers have become resistant to insecticides.
-Some farmersgrow rice plants in small sections to try to avoid this.
How is a reduction in soil fertility a disadvantage of monocolture?
- Farmers often grow the same crop on the same land, year after year.
- The crop plants all need the same mineral ions, so they are depleted from the soil.
- Farmersneed to constantly use fertiliser.
- Or…. grow a mix of different crops / at different times of the year to maintain a mineral balance
What are the main methods of livestock production?
- extensive livestock production
- intensive livestock production
How does intensive livestock production work?
large numbers of animals are kept in a relatively small area (common in developed countries).
* Farmers use: high energy food to feed animals
* Farmers regularly use medication to stop disease development
* Animals kept in temperature-controlled buildings to maximise growth
How does extensive livestock production work?
livestock are kept outside, they graze on grass or are brought cut vegetation to eat. The livestock don’t take too much from the environment, and don’t do too much damage.
What are the advantages of intensive farming/ livestock production?
- It can help provide more food to people, often at a lower price
- Therefore fewer people go hungry (including those in poverty)
- It takes up less space (land), and therefore perhaps habitats for other species.
What are the disadvantagesto intensive farming
- Welfare issues for animals suffering in crowded conditions.
- Disease can spread easily among animals.
Insome countries this is dealt with by using a lot ofantibiotics – therefore there is opportunity for antibiotic resistance. - The waste from intensive farming can pollute land and waterways.
Welfare issues for animals suffering in crowded conditions. - Disease can spread easily among animals.
Insome countries this is dealt with by using a lot ofantibiotics – therefore there is opportunity for antibiotic resistance. - The waste from intensive farming can pollute land and waterways.
- Large quantities of watermust be provided. Sometimes thistakeswater from surrounding environment (affecting local species)
How are habitats destroyed?
- Deforestation
- Mining for minerals
- Polluting
- Removal of species
How are habitats destroyes through deforestation?
We cut down vegetation to use the land for farming/building houses/roads. (Deforestation)
How are habitats destroyed through mining?
We damage habitats through mining for materials like metal ores, sand, gravel, fossil fuels.
The mine destroys the habitat by removing soil & vegetation
And water flowing away from the mine can be toxic. It can enter soil & rivers
How are habitats destroyed by polluting?
We add pollutants to land and water, that kill organisms living there and therefore change the habitat.
Give an example of how habitats are destroyed when key species are removed.
Collecting live corals from coral reefs endangers the whole ecosystem.
Corals contain tiny photosynthetic algae, which are the start of every food chain on a coral reef.
Deforestation
the cutting down of large numbers of trees
Why do humans do defprestation>
- Use wood for fuel
- Use wood for building
- Use land for agriculture
What are is the concequence of rainforest deforestation?
- can lead to species extinction if there is not enough habitat / resources for the species to reproduce.
- soil erosion
- water cycle dissruption
- social economics and politics
What is special about rainforests?
Rainforests are places with extremely high biodiversity. Many species living in one place.
What is the process and concequence of soil erosion?
- When rainforest is cut down, the soil under the trees is exposed to rain.
- The soil in rainforests is thin, and therefore quickly washes away. Especially without plants roots to help it bind together.
- This soil erosion makes it very difficult for the rainforest to grow back again.
- The soil can be washed into rivers, filling them with soil and causing flooding.
What is the process and concequence of chnages in the water cycle due to deforestation?
- Trees use a lot of rainwater to take up by their roots and eventually transpire.
- If trees are gone, the rainruns off the soil and intorivers – much less goes back into the atmosphere as water vapour.
- Air becomes drier = less rain falls=people struggle to grow crops
What is a factor that prevents deforestation from being dtopped/
Social economics & politics
* Most tropical rainforests are in developing countries, some of which where people are generally poor.
* Cannot expect someone who is pooryet needs to produce food to feed theirfamily not to clear land for agriculture.
… unless you can offer an alternative, which is what some charities and NGOs aim to do (provide options for other sources of food production and income)
In some places, the government may be the main driver behind deforestation. (lobbying)
Pollution
adding something to the enviornment that harms it.
What are the sources of pollution?
- greenhouse gases and climate change
- Eutrophication
- Plastics
Greenhouse gases
gases such as carbon dioxide and methame that trap heat within the atmosphere.
The greehouse effect
the heating effect on the Earth of trapping heat by greenhouse gases. Note: this is natural and useful, without it Earth would be too cold for any life.
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