U2T6 - Human Impact Flashcards
What do highly developed countries do in respect to agricultural strategies?
Adopt strategies which max economic gain which impacts badly on biodiversity.
What has happened as farming has changed from more traditional methods?
Decreased biodiversity due to habitat loss.
What are 4 ways farming has affected biodiversity?
Increased use of monoculture, nutrient enrichment of soils, loss of hedgerows + woodland + increased pesticide use.
How has increased use of monoculture affected biodiversity?
Whole area of farmland would grow 1 crop (barley/perennial rye grass for silage/grazing). Pest buildup specific to crop + specific nutrients reduced as certain crop may rely on certain nutrient types. All lack of delay due to harvesting can reduce decomposition + nutrient recycling.
How has nutrient enrichment of soils affected biodiversity?
Monoculture can lead to reliance on artificial fertilisers (may be used to maintain high stocking rates on livestock farms) High nitrate levels leads to target crop outcompeting slower growing crops. Fertiliser can lead to decreased pod size + loss of soil crumb structure which can lead to soil erosion.
How has loss of hedgerows + woodland affected biodiversity?
Hedgerows act as wildlife corridors linking areas of woodland/other species rich environments. Facilitate movement + dispersal of many species (butterfly/insects) May be removed to increase land available for agricultural practices/facilitate operation of agricultural machinery. Loss of habitat + food occurs. Also protect land from exposure to rain/wind so can lead to increased soil erosion.
How has increased pesticide use affected biodiversity?
Used to max crop production. Broad-spectrum pesticides may be used + these kill other organisms + soil microorganisms which cause decomposition. Also kill natural predators of pests so pest resurgence occurs. Herbicides reduce biodiversity (eliminates non-crop species) + food available to animal species. Pesticide overuse causes some species to be resistant so bioaccumulation occurs.
What does polyculture allow?
Provides variety of habitats for insects + other soil organisms + variety of food sources for more complex food webs. Crops carefully chosen so soil not stripped of certain nutrients, reducing fertiliser need. More efficient way to use resources e.g. water when shallow + deep rooted plants grown together. May reduce pest nums. Less profitable than monoculture. Mostly due to economies of scale which are possible with large monocultures.
What are some of the guidelines for hedgerow conservation + maintenance?
Hedge cutting confined to Autumn + Winter on 2 yearly cycle to avoid disturbing nests + destroying food sources (berries), hedges cut to A shape to provide diff widths + microhabitats, variety of plant species used to increase microhabitat variety + some trees left to act as habitats + bird song posts. Put double fence on either side of hedge so it can establish as sheep may graze. Variety of native plants for biodiversity.
How has increased use of organic fertiliser promoted biodiversity?
Helps soil fertility. Manure helps preserve soil crumb structure as humus holds it together. Releases nutrients slower + loss of minerals due to leaching is reduced as plants have greater capacity to uptake nutrients due to gradual release. Difficult to store + have unknown nutrients. If specific nutrient requirements of crop are known, these are matched with artificial requirements.
What does integrated pest management do?
Includes using narrow-spectrum pesticides which only affect target species + crop rotation so there’s increased biodiversity + natural predators.
What are the advantages of biological control?
Reduces environmental harm as no bioaccumulation in food chains/environmental chemical damage, targets only pest species so reduces damage to other organisms, pest resistance risk reduced (some organism may have mutation + not targeted by pesticides so can reproduce so disease resistant organisms increase when using pesticides), pest resurgence unlikely + reduces costs if successful (no pesticide, little labour)
What are the disadvantages of biological control?
Not always successful, pest numbers reduced below level of economic damage but not eliminated, control agent must be able to survive in new habitat.
How can pest management be established?
Using predator strips (rough undisturbed grass at field hedges). Encourages natural predators to establish.
What are 3 advantages of predator strips at field margins?
Provides habitat for many species (vertebrate + invertebrate), some insects in it over Winter act as predators of crop pests in Spring, reducing crop losses + pesticide needs, others act as food for higher trophic levels + some vertebrates (wood mice) are food source for larger vertebrates (Barn owls). Cost to farmer as less productive land to farm but if field margins larger than 1m created, subsidies available to farmer to offset productivity loss.
