20 Human influences on ecosystems Flashcards
How have humans increased food production?
1) agricultural machinery to improve efficiency
2) chemical fertilisers to improve yields
3) insecticides to improve quality and yield
4) herbicides to reduce competition with weeds
5) selective breeding to improve production by crop plants and livestock
monoculture
growing just one crop species in a field at a time
advantages of monocultre
Specialised harvesting techniques - one type of machine can collect all the crops
Highly selected strains - varieties of plants with desirable characteristics can be matched to the conditions
mineral/water requirement: scientists can work out exactly what the crop needs
disadvantages of monoculture
poor wildlife foods: very little variety of weeds for insects and birds
spread of disease: plant pathogens, such as potato blight fungus, spread easily since it has its ideal food everywhere
loss of genetic variety: change in environmental resistance could damage or kill all of the plants
Damage to soil: same minerals are drained away by many copies of the same plant
How do farmers bring the minerals back into the soil?
By burning their crops
Advantages of intensive livestock production
high yield of food, more efficient, affordable food prices, sustainable supply of food
Disadvantages of intensive livestock production
poor livng conditions and hygiene, large amounts of methane is produced, hormones and antibiotics that are used to increase yield can pass to humans
biodiversity
number of different species that live in an area
reasons for habitat destruction
1) increased area for housing, crop plant production and livestock production
2) extraction of natural resources
3) freshwater and marine pollution
What happens when humans alter the food webs/chains
Through altering food webs and food chains, humans can have a negative impact on habitats
undesirable effects of deforestation
- Roots die so cannot bind soil = soil erosion.
- silting of rivers
- reduced soil fertility
- no trees to absorb water = increased risk of flooding
- increased rate of evaporation = desertification
- loss of habitats
- disruption to food chains
- endangered species/loss of biodiversity
The stages of Eutrophication
- Minerals in fertilisers leached from soil by rain
- More mineral ions allow the increased growth of algae which blooms, blocking light getting to larger plants
- Large plants die as they can’t photosynthesise and this provides food for decomposers
- Dead plants are decomposed by bacteria which can multiply rapidly as there is lots of food. Lots of bacteria respiring uses up oxygen in the water.
- Oxygen levels are so low that animals like fish can’t respire so they die
Eutrophication
mineral ions, such as nitrates in sewage and fertilisers, cause growth of microscopic plants (algae) increases but this leads eventually to too much dead matter.
Effects of non biodegrable plastic in aquation and terrestrial ecosystems
Animals becoming entanglement in marine debris, including plastic bags, may cause starvation, choking, laceration, infection, reduced reproductive success, and mortality.
Can block light and prevent plants from photosynthesising.
May release toxins into the environment
May block flow of river
sustainable resource
produced as rapdily as it is removed from the environment so that it does not run out
