Control of biotic habitat features

• Food -

  • the survival of an animal species may be increased if suitable conditions are provided for its food species for example wildflower grasslands that support seed-eating birds
  • birds have different feeding methods to find food and avoid interspecies competition:
  • Dunlin eat invertebrates it finds in shallow sediments
• Control of predation -

  • will improve the survival of animals for example by providing island breeding sites for nesting water birds that cannot be reached by terrestrial predators such as foxes, if predators cannot be excluded, they may be trapped, removed or culled
  • introduced mammal predators are often a problem on islands which have no indigenous mammal predators, where colonies of ground nesting birds became established
  • eradication programmes have been carried out on many islands
• Control of competitors -

  • the survival of species may be increased if competitor species are controlled
  • for example removing invasive rhododendron bushes allows wildflowers to grow because they are not outcompeted for light
• pollination -

  • many flowering plants need insects to pollinate their flowers so they can produce seeds
  • they attract pollinators such as bees using attractive flowers that produce sugar-rich nectar
  • it may be necessary to have a range of other flowering plant species present with different flowering times so that the insects have food available all through the seasons that they are active
• seed dispersal -

  • some animal species are important to plants for dispersal of their seeds such as seed eating birds
• Control of pathogens -

  • disease is a density dependant factor which can maintain the health of the surviving population by removing the weakest individuals
  • however introduced diseases can wipe out indigenous species that have no resistance to them
• Species re-introductions -

  • some habitats have been changed by human activities but still retain many of their original features
  • it may be possible to restore the habitat by recreating more natural conditions
  • many species will colonise these habitats naturally especially the more mobile species such as flying insects and birds
  • other species that are less mobile may fail to colonise and may have to be re-introduced
• Re-wilding in Yellowstone national park USA-

  • the Gray Wolf was the top predator but they were exterminated by 1926 and this caused changes in populations of other species
  • wolves have been re-introduced since 1955
  • deer populations have declined, so fewer young trees are killed
  • having more trees has allowed beaver populations to increase
  • the dams that beavers create have increased the area of wetland habitats
  • wetland species have become more common and overall biodiversity has increased
• Re-wilding in Scotland-

  • most of Scotland used to be covered in a mixed forest including pine, oak, birch and rowan trees
  • these were largely cleared for fuel and replaced with moorland grazed by sheep and deer
  • the removal of the grazing species and reafforestation will allow the recovery of popultions of animals
  • European Beavers have been reintroduced and there are proposals of reintroducing Eurasian Lynx and Grey Wolves
• Abiotic factors in forests -

  • tall foliage may cause reduced light levels due to shading
  • transpiration increases humidity
  • vegetation acts as a windbreak and reduces wind velocity
  • decomposition of dead vegetation increases nutrient availability
• Control of ecological succession - plagioclimax maintenance

  • successful conservation of wildlife habitats does not just involve establishing a suitable habitat area then protecting it from damaging external influences
  • the natural changes that take place during ecological succession may reduce its value for the species that are present during any individual stage of succession
• Plagioclimax community -

  • in many areas the activities that disturbed the climax community are carried out regularly so a new community fo species develops
  • many are important to humans like grazed farmland
  • they are maintained as plagioclimaxes for human use but they are also colonised by wildlife species
  • the traditional human activities that produced plagioclimaxes may change which could move the conditions outside the range of tolerance of the wildlife species living there
• Conservation programmes to protect specific plagioclimax species -

  Grazing :

  • prevents the establishment of taller plants and maintains grassland plagioclimax
  • conservation grazing is often used to maintain habitats such as chalk grassland and flower rich meadows
  • trampling by livestock produces bare ground which is important for the germination of wildflower seeds and to produce the warmer clearings needed by some invertebrates and reptiles
  • animal dung produces small areas with higher nutrient levels which may support different plant species and many invertebrates
  • sheep eat shorter grass
• Mowing conservation -

  • this removes the same vegetation that would be removed by grazing herbivores but it also removes the thorny, stinging or bad tasting plants that herbivores might avoid
• Burning -

  • this can be used to remove vegetation that would not be eaten by grazing animals
  • it creates the open, unshaded areas needed for the growth of young heather plants that will re-establish the heathland
  • heather seeds lie dormant in the soil until they are stimulated to germinate by the heat of the fire
• Coppicing -

  • trees are cut to ground level every 3-30 years depending on the intended use of the harvested branches
  • in many areas that were traditionally coppiced, about 0.5 ha was cleared each year with a rotational cycle of 8 years
  • so a coppiced woodland would be a patchwork of areas of woodland of different ages, each being suitable for its own community of wildlife species
• Pollarding-

  • this is similar to coppicing but with branches cut above the height at which deer or livestock could eat the re-growing branches
• Population control -

  • may be necessary to actively control the populations of selected species either by increasing or reducing them depending on which species are desirable
  • the release of captive bred individuals will boost the wild population and help support the population if the population size is low , the breeding rate is low or the mortality rate is high
  • the population of undesirable species may be controlled to reduce predation or competition
  • restoration and maintenance of a valuable wildlife habitat often involves the removal of unwanted species