Human Impact on Biodiversity

• Biodiversity


  Reflection of both the number of species in an area and how evenly distributed the numbers of living organisms are spread across the range of species present
• Agricultural practices can significantly reduce biodiversity or help promote biodiversity depending on the strategies used
• In highly developed countries such as Northern Ireland, the agricultural strategies that maximise productivity and economic gain have a serious impact on biodiversity
• Intensive agricultural practices


  • Practices designed to maximise productivity (increased food production) and profit
• Agricultural intensification in Northern Ireland has resulted in a very significant reduction in biodiversity as a consequence of habitat loss and habitat change
• Monoculture

  Whole areas of farmland are often given over to one species of crop
• Monoculture is a common practice on large farms due to the 'economies of scale' involved in ground preparation, planting and harvesting
• Monoculture reduces biodiversity and has other problems including the build-up of pests specific to the crop being grown and the depletion of particular minerals in the soil
• Nutrient enrichment of soils, often associated with monoculture, allows the target crop to outcompete and eliminate many other slower growing species
• Nutrient enrichment can also lead to loss of soil crumb structure, which can lead to increased soil erosion
• Loss of hedgerow and woodland, and increasing fragmentation, leads to loss of biodiversity through the loss of habitat and food for many hedgerow species
• Hedgerows act as wildlife 'corridors,' linking areas of woodland or other species-rich habitats, facilitating the movement and dispersal of many species
• Removal of hedgerows can occur for reasons such as increasing the area of land available for agriculture and facilitating the use of larger agricultural machinery
• Pesticides are used to maximise crop production through eliminating pests that reduce production
• Broad-spectrum pesticides can reduce biodiversity by killing organisms of species other than the intended target
• Pesticides can eliminate natural predators of the main pest and cause pest resurgence, allowing the pest to return in even greater numbers
• Herbicides reduce plant biodiversity by eliminating non-crop species and reduce the variety of food available to animal species, thereby reducing animal species diversity
• Some species can become resistant to pesticides and there can be issues with bioaccumulation (the build-up of concentrations in the tissues of organisms progressively higher trophic levels)
• Polyculture


  Growing a range of different crops at the one time or sequentially in the one place
• Polyculture provides a wider range of food sources and habitats for wildlife, leading to a greater number of, and more complex, food webs
• Crop rotation


  Planting different crops in the same field over a period of years
• Crop rotation helps conserve soil fertility as the different crops make different demands on soil nutrients, and can be particularly effective when nitrogen fixing crops are part of the cycle
• Crop rotation also reduces the likelihood of a build up of pests specific to one crop in an area
• Organic fertiliser


  Farmyard manure
• The use of organic fertiliser and the consequent decrease in the use of artificial fertiliser helps promote soil fertility and preserve soil crumb structure
• Organic fertiliser releases nutrients at a slower rate with less mineral loss due to leaching, as the plants can make better use of a greater proportion of the more slowly released nutrients
• Planting new hedgerows and restoring and maintaining existing ones helps support biodiversity
• Biodiversity friendly hedgerow trimming


  • Allowing hedgerow trees to grow to maturity at intervals, only trimming on a 2-3 year rotation, trimming during late winter to avoid bird nests, maintaining a range of hedge heights and widths
• When establishing a new hedgerow, or carrying out substantial repairs to an existing one, it is important to protect the young hedgerow trees/shrubs from grazing
• It is also important to plant a mixture of woody species in a new hedge with associated biodiversity benefits, rather than a monoculture of hawthorn
• Integrated pest management


  Approaches that include the use of narrow spectrum pesticides and strategies such as crop rotation to prevent the build-up of pest populations
• Biological control


  Deliberately introducing predator or pathogenic species that target the pest
• Biological control benefits the environment by reducing the need for chemical pesticides and because broad spectrum pesticides often do not work very well
• With effective biological control, the introduced predator integrates naturally into the ecosystem, building a sustainable population and therefore does not need to be continually re-introduced
• Biological control has limitations and is not always successful, as the pest will not be totally eliminated and the biological control species may not be able to adapt and thrive in the 'unnatural' crop ecosystem
• Inappropriate farming practices can also harm the environment and reduce biodiversity in a number of other ways, including the pollution of waterways
• Organic pollution


  Pollution of water by organic material such as sewage, slurry and silage effluent
• Eutrophication


  Another cause of water pollution, related to but distinct from organic pollution
• Organic pollution leads to a population explosion of saprobiotic bacteria that subsequently use up much of the oxygen in the water due to aerobic respiration
• Biological Oxygen Demand (BOD)


  Indication of water quality, measured as the usage of oxygen in the water