Module 6.3.2- Populations and sustainability

• Population growth curve

  Phase 1- a period of slow growth

  Phase 2- a period of rapid growth

  Phase 3- a stable state

  
• Population growth curve- Phase 1 (slow)


  small numbers of individuals that are initially present reproduce increasing the total population. as the birthrate is higher than the death rate, the population increases in size

  
• Population growth curve- Phase 2 (rapid)

  as the number of breeding individuals increases, the total population multiplies exponentially

  
• Population growth curve- Phase 3 (stable state)

  further population growth is prevented by external constraints. during this time the population size fluctuates, but overall its size remains relatively stable

  
  

  birth rate is approximately the same as death rate

  
• Why do populations tend to decline and so preventing further growth

  Due to limiting factors which can be split into abiotic and biotic factors

  
  

  e.g.

  abiotic- temperature, light, pH, water/oxygen availability

  biotic- predators, disease, competition
• Carrying capacity

  The maximum population size that an environment can support
• Immigration

  the movement of individual organisms into a particular area increasing population size
• Emigration

  the movement of individual organisms away from a particular area decreasing population size
• Density independent factors

  limiting factor that affects all populations in similar ways, regardless of population size e.g. earthquakes, volcanic eruptions, fires, storms
• Interspecific competition


  competition between different species
• Intraspecific competition


  competition between members of the same species
• Effects of interspecific competition

  • two or more different species compete for the same resources
  • therefore less resources are available for the species
  • if one species is better adapted, it will outcompete other species, therefore, reducing them
• Competition exclusion principle


  no two species can occupy the same niche in the same habitat at the same time
• Effects of intraspecific competition

  Stage 1- when resource is plentiful in habitat, all organisms have enough resource increasing population size

  Stage 2- resources are now limited, decreasing population size

  Stage 3- now less competition, population size increases since more organisms survive and reproduce

  
• Predation

  An interaction in which one organism (predator) kills another (prey) for food.
• Predator-prey relationship population changes graph

  Stage 1- increase in prey, more food for predator, predator pop. increases

  Stage 2- increase in predator, eats more preys, prey deathrate > birthrate

  Stage 3- decrease in predator, more prey survive increasing prey population competition for food increases, decreasing predator population

  Stage 4- decrease in predator, more prey survive increasing prey population

  
• Conservation


  maintenance of biodiversity through human action or management

  approaches also include reclamation(process of restoring ecosystems that have been damaged or destroyed)
• Preservation


  protection of an area by restricting or banning human interference, so that the ecosystem is kept in its original state
• Importance of conservation (economic, social , ethical )


  Economic- provide resources that humans need to survive and to provide an income

  Social- many people enjoy the natural beauty of wild ecosystems. can provide a means of relaxation and exercise

  Ethical- all organisms have a right to exist and we do not have the right to decide which organisms can survive. we also have a moral responsibility for future generations
• Sustainable resource


  Renewable resource that is being economically exploited in such a way that it will not diminish or run out.
• Aims of sustainability


  
  

  • Preserve the environment
  • Ensure resources are available for future generations
  • Allow humans to live comfortably
  • Enableless developed countries to develop through exploiting natural resources
  • Create more balance between countries
• Name the technique that is often used to produce sustainable timber on a small scale

  Coppicing
• Coppicing


  The process where trees are cut to ground level every few years to encourage new growth. The regrowth produces long narrow stems

  
• Uses of coppicing

  Fencing, burning
• What is rotational coppicing and how does it maintain biodiverisity?


  Allowing small trees to grow and then cut of their shoots, allowing them to regrow, by doing this rotationally you protect habitats and the tree which will grow again in 7-20 years to be harvested again.

  trees never grow back enough to block out light, hence succession cannot occur ( plagioclimax) so more species survive therefore maintaining biodiversity
• Pollarding


  cut the trunk higher up a tree to encourage new growth at the top so animals cannot eat new shoots
• Large-scale timber production


  felling large areas of forest destroying them and so will not regrow.
• Sustainable large-scale timber production


  
  

  • practice selective cutting including removing only the largest trees
  • replace trees through replanting
  • plant trees an optimal distance apart to reduce competition
  • manage pests and pathogens to maximise yields
  • ensure areas of forest remain for indigenous people
• Disadvantages of large-scale timber production

  -

  • habitats destroyed
  • soil minerals reduced
  • bare soil left is susceptible to erosion
  • trees are important for binding soil together, removing water from soil, and maintaining nutrient levels through their role in the carbon and nitrogen cycles
• Common Fisheries Policy of the European Union

  Fishing quotas provide limits on numbers of certain species of fish that are allowed to be caught in a particular area

  allows fish to reproduce sufficiently to maintain population
• Techniques, other than fishing quotas, for sustainable fishing

  
  

  • use of nets with different mesh size e.g. using a large mesh to let immature fish escape
  • allowing commercial and recreational fishing only at certain times of the year
  • introduction of fish farming to maintain supply of protein food, whilst preventing the loss of wild species
• Masai Mara National Reserve (MMNR)

  In southern Kenya and is primarily a savannah ecosystem that is actively being managed to balance the needs of humans and the need for conservation.
• Farming (grazing)- MMNR

  Traditionally the Masai Mara has been used by local tribes for livestock grazing. In the past, the Masai practiced a traditional method of farming known as semi-nomadic farming. Tribes frequently moved depending on climate variation and the presence of tsetse flies. This allowed vegetation time to recover from animal grazing whenever the farmers moved on to another area. Grazing is now limited to areas on the edge of the reserve, as local tribes are prevented from entering the park. Populations have grown in these marginal areas. Larger herds graze the grassland areas, and more trees are removed for fuel. As the vegetation is removed the risk of soul erosion increases.
• Cultivation- MMNR


  level of cultivation has increased in recent years. As grassland has been converted into cropland, natural vegetation is removed, and nutrients in the soil are used up. Over time this leads to a reliance of fertilisers for effective crop growth.
• Ecotourism


  A form of tourism, based on the enjoyment of scenic areas or natural wonders, that aims to provide an experience of nature or culture in an environmentally sustainable way.
• Key principles of ecotourism:


  
  

  • Ensure that tourism doesn't exploit the natural environment or local communities
  • Consultand engage with local communitieson planned developments
  • Ensure that infrastructure improvements benefit local peopleas well as visitors
• Disadvantages of ecotourism


  tourist movements may contribute to soil erosion and other habitat changes
• Terai region of Nepal: Ecosystem

  In the southern part of Nepal which is a rich agricultural area. It is an area of extreme biodiversity
• Peat bog: Ecosystem


  Region of wet, spongy ground that contains decomposing vegetation
• Management techniques in environmentally sensitive areas

  -limiting areas tourists can visit

  -controlling movement of livestock

  -introducing anti-poaching measures

  -replanting of forests and native plants

  -limiting hunting through quotas and seasonal bans