Human Impact on Biodiversity Flashcards
What does biodiversity reflect?
The number of species in an area and how evenly distributed the numbers of living org are spread across the range of species present
What is the effect of agricultural intensification?
Large reduction in biodiversity
What are the disadv of monoculture?
Reduced biodiv
Build up of pest spec to crop being grown
Growing same crop yr after yr on same land can lead to red of particular minerals in the soil b/c each successive crop has had the same mineral ion req
Crop is harv b4 decay/ decomposition can take place and return minerals to the soil
What are the disadv of nutr enrichment of soils:
High levels of nitrate encourage fast growth of particular crop, is harmful to biodiversity, it allows the target crop to outcompete and eliminate many other slower growing species
Can also lead to loss of soil crumb str, which can lead to increases soil erosion
What are the disav of the loss of hedgerows?
Leads to loss of biodiversity- through loss of habitat and food for many hedgerow species. This impacts on other species higher up the food chain
Loss of wildlife corridors. Hedgerows act as wildlife corridors linking areas of woodland or other species-rich habitats. Animals such as small mammals, birds, insects i.e butterflies use these for movement from place to place
Soil erosion can take place due to land being more exposed to wind and rain and the reduction of the soil binding role of tree and shrub roots
What is a pest?
Is a species that damages a valuable/ commercial crop species causing economic damage
Descr affect of broad spectrum pesticides:
(Insecticides) can reduce biodiversity by killing organisms of species other than the intended target. Kill soil organisms that are involved in decomp and improving soil str
What can pesticides do in terms of predators?
Can eliminate natural predators of the main pest and cause pest resurgence allowing the pest to return in greater numbers
How do herbicides reduce biodiversity?
This type of pesticide used to kill weeds/ competitor plant species) reduces biodiversity (kills non-crop species) and reduces the variety of food avail to a variety of animal species
What happens when species become resistant to pesticides?
There can be issues with bioaccumulation (build up of conc in the tissues of organisms at higher trophic levels)
What is polyculture?
Growing of a range of different crops at the one time or sequentially in the one place
What are the adv of polyculture?
Wider range of food sources and habitats for wildlife, leading to more/ complex food webs
Crop rotation is the planting of different crops in the same field over a period of yrs. This helps conserve soil fertility as the different crops make different demands on soil nutrients
Crop rotation can improve soil fertility when N-fixing crops (peas, beans, clover) are part of the cycle
Crop rotation reduces the likelihood of a build-up of pests specific to one in an area
What are the adv of increased use of organic fertilisers?
Helps preserve soil crumb str as the humus in the farmyard manure holds the crumb str together
Farmyard manure releases nutrients at a slower rate with less mineral loss due to leaching, as the plant can make better use of the more slowly released nutrient
What are the disadv of increased use of organic fertilisers?
More difficult to spread and store
Nutrient content is more variable
How does biodiversity friendly hedgerow trimming will further increase biodiversity?
Allowing hedgerows trees to grow to maturity at intervals in the hedge
Only trimming on a 2-3 yr rotation. This allows shrubs to flower and produce berries (providing food for birds over the winter months)
Trimming during late winter ( Jan-Feb) to avoid the destr of birds nests during the spring and summer and allowing berries to dev in the autumn
Maintaining a range of hedge heights and widths by staggering trimming regimes. Different bird species have different pref for hedgerow heights and widths.
Hedges cut in a A shape as opposed to a box shape can be particularly diverse as this allows more light, to penetrate to the ground level
How does protecting newly planted hedge/ repairing an existing one increase biodiversity?
A double fence can be placed around the hedge, this both protects the young hedge and forms an effective boundary in the interim. Once the hedge is established/ repaired the fence is removed
How does integrated pest management and biological control increase biodiversity?
May kill target pests but also eliminate the natural predators of the pest and kill soil organisms important in the decomp of organic matter and the maintenance of soil fertility
How do narrow spectrum pesticides increase biodiversity?
Only affect the target pest species have now ben introduced
How does crop rotation increase biodiversity?
Helps prevent the build-up of large pest populations as the absence of a specific crop for a few yrs may prevent the pest being able to complete its life cycle.
Biological Control
Involves deliberately introducing predator species that target the pest. This is an alternative to using chemical pesticides.
What are the adv of effective biological control?
No chem damage to the env/ bioaccumulation in the food chain
Biological control targets only the pest species
The dev of res by the pest is unlikely
Pest resurgence unlikely
Needs little additional action and saves money on the continued use of pesticides
What are the limitations of biological control?
Pest will not be totally eliminated- its density is reduced (to below the level for economic damage)
Biological control will only work if the biological control species can adapt and thrive in the ecosystem into which it is introduced
How do predator strips increase biodiversity?
Small areas of rough grass left undistributed at field hedges will encourage the increase in numbers of many crop pests natural predators on the farmland- ladybirds can thrive in relatively species-rich predator strips- undisturbed thru the absence of fertiliser or pesticides) and feed on the harmful aphids that damage the crops
What are the main ways that waterways are polluted?
Urbanisation
Industrial Waste
Poor Sanitation Levels
Agriculture