Sand dunes Supplement- slides

• Sand dunes


  Coastal habitat

  
• Sand dune profile


  • Available nutrients increase
  • Salinity decreases
  • Shelter increases
  • Age of dunes increases
• You can see by the above image how much species increases and varies as we go further into the sand dunes
• Plant succession


  1. Evolution of plant communities

  2. From pioneer species to climax vegetation

  3. Related to change in the environment

  4. Change brought about by the plants themselves

  5. This change then favours new species
• 'Plants are the architects of their own demise'
• First stage is the beach

  1. Sand accumulates on the beach from longshore drift or onshore currents

  2. At low tide, the sand dries out allowing the prevailing winds to move the loose sand up the beach
• Fore dune


  • First plants to colonise are Lyme grass, sea couch grass and marram grass
  • These plants are drought-resistant and capable of withstanding burial by the shifting sand
  • As they grow up through the sand, they help trap more sand and so the dunes increase in height
• Yellow dunes


  • Show a greater diversity of plants as conditions become more favourable
  • As plants die and decay, a humus layer builds up and this traps both water and nutrients
  • The pH is now only slightly alkaline (about 7.5)
  • There is more shelter and less salt spray
• Grey dunes


  • Much more stable
  • Mosses and lichens fill the few remaining spaces between plants so that vegetation cover may reach 100%
  • There is shelter from the harshest winds
  • A true soil begins to form
• Dune slacks


  • Found in between the more mature dunes
  • The water table reaches the surface causing seasonal or even permanent water logging and surface water
• Mature dunes


  • Found several hundred metres from the shore
  • Left undisturbed these dunes develop a soil which can support shrubs and trees

  
• Dune succession order


  • Grey Dunes
  • Dune Slacks
  • Yellow Dunes
  • Mature Dunes
  • Fore Dunes

  
• The dune system is a fragile one and even small amounts of damage can cause long-term problems
• Humans wander onto and through the dunes in increasingly large numbers and small paths which wear through the vegetation cover soon turn into deep gullies as the wind uses the opportunity to carry away the sand
• Rabbits in their hundreds dig large holes in the dunes
• Eventually, large hollows, called blowouts, are formed and up to 50% of a mature dune may be lost
• Plants die and due to loss of habitat, insects, amphibians, birds and animals also disappear
• Dune management


  1. Fencing off at least part of the dune system so that public access is restricted

  2. Allowing damaged dunes to recover and/or ecologically important sections to be protected

  3. Public access to beaches may be via fenced-off pathways

  4. Along the footpaths, information boards can be used to educate the public about why the dune system is important and how they can avoid damaging it

  5. Blowouts can be repaired by trapping the loose sand with barriers - sometimes old Christmas trees are used

  
• Rising sea levels are a major threat facing not just Sand Dunes but any major habitat along any costal area
• Rising sea levels


  Coastal habitats would be destroyed as animals and plants in the area are not adapted to living in these conditions (under the sea)
• Areas of low lying relief like areas of London and Willingdon would definitely disappear with rising sea levels
• Several engineering schemes like the Thames flood barrier have been put in place to prevent rising sea levels
• Reducing global warming by reducing emissions and pollution in the air is a possibility to prevent rising sea levels, but effects are already taking place so solutions for now are needed
• If the sea level were to rise to its full capability, much of the UK would be submerged