Ecosystems

• Ecosystem

  A biological community of interacting organisms and their physical environment
• Provider of goods


  • Products that can directly be derived from an ecosystem e.g., timber, nutrients, and medicine
• Provider of services


  • Functions of the biome that help serve the planet
• Types of ecosystem services

  • Provisioning services
  • Regulating services
  • Cultural services
  • Supporting services
• Provisioning services


  The direct products of the ecosystem e.g., the production of food
• Regulating services


  Services linked to other physical systems and keep areas and the whole planet healthy e.g., natural CO2 regulation
• Cultural services


  Non-material benefits obtained by ecosystems e.g., aesthetic views
• Supporting services


  Keep the ecosystem healthy so it can provide other services e.g., soil formation or nutrient cycling
• Biome


  A major terrestrial ecosystem of the world
• Tropical rainforests


  • Hot all year round – no seasonality
  • High amounts of rainfall
  • High biodiversity
  • Found at the equator (0N)
• Tropical grassland (Savannah)


  • Hot, seasonally dry with rainy season
  • Plains of grass
  • Found at low latitudes (10N)
• Deserts


  • Very hot
  • Little rainfall
  • Found at low latitudes (20N)
• Temperate grassland


  • Plains of grass
  • Hot summer and cooler winters
  • Found at middle latitudes (40N)
• Temperate/deciduous forests


  • Cool and rainy
  • Trees lose their leaves in autumn
  • Four distinct seasons
  • Found at middle latitudes (50N)
• Taiga/boreal/coniferous forests


  • Cold temperatures
  • Harsh climate with low rainfall
  • Trees do not lose their leaves
  • Found at high latitudes (70N)
• Tundra


  • Cold
  • Treeless
  • Little rainfall
  • Found at pole locations (80/90N)
• Richness


  The number of genetically or functionally related species (species richness)
• Evenness


  The more equal species are in proportion to each other the greater the evenness of the site and therefore the more biodiverse. A low evenness indicates that a few species dominate the site
• Simpson's Diversity Index


  D = 1 – [∑ (n / N) 2]

  n = number of individuals

  N = total number of individuals
• Simpson's Diversity Index is a measure of diversity which takes into account the number of species present, as well as the relative abundance of each species. As species richness and evenness increase, so diversity increases.
• Why measure biodiversity?

  It is often measure because high biodiversity is perceived as synonymous with ecosystem health. More diverse communities are believed to have increased stability and productivity, and resistance to invasion.
• Threats to biodiversity


  • Direct threats - Relate to either physical or human actions that cause immediate harm

  Indirect threats - Actions that consequently cause harm. E.g., climate change.
• Climate change


  • High impact storms destroy habitats

  Changing temperatures and rainfall patterns affect the least tolerate species

  Sea level rise may occur too quickly for species to adjust – coral reefs cannot survive in deep water

  Droughts kill plants and animals

  Ice caps are melting resulting in habitat loss for Polar Bears

  Increasing the frequency and extremity of El Nino – reduces fish stocks in Peru
• Deforestation


  • Destroys habitats

  Breaking up (fragmentation of woodland ecosystems)

  Impacts the range and breeding ability of some species

  Minimum dynamic area (MDA) affected

  e.g., deforestation in the Amazon for cattle ranching
• Invasive species


  • e.g., In New Zealand the Brushtail Possum has no predators and each night and estimated 70 million possums eat 21,000 tonnes of vegetation

  e.g., in the USA the European Purple Loosestrife has invaded and kills off habitats by outgrowing native species
• Pollution

  • Chemicals are added to the environment by humans e.g., pesticides and fertilizers

  Fertilizers cause algae blooms in the ocean (Eutrophication)

  DDT used to kill mosquitos causes negative effects further up the food chain like Ospreys laying thin eggs
• Overexploitation


  • Logging, hunting, and fishing

  1 billion people are dependent on fish as their main source of protein – overfishing
• Reduction in habitats causes higher population densities which encourages the spread of disease
• Ecosystems at greater distances from human influences are more likely to be threatened by indirect action than direct action.
• Tropical rainforests


  • Fragile due to their high biodiversity
  • Loss of ecological niches dramatically effect food webs
• Deforestation of tropical rainforests

  1. For food

  2. For minerals

  3. For timber

  4. Due to population pressure
• Deforestation of tropical rainforests

  • Degrades the soil (less interception leads to more leeching and overland flow = less nutrients)
  • Less nutrient input from leaf litter
• Tropical rainforests hold 50% of world biodiversity, so impact of deforestation is more acute
• Tropical rainforest land is easily degraded
• Coral reefs


  • Threatened by ocean warming - algae loss
  • Threatened by ocean acidification - coral bleaching
• Threats to coral reefs

  • Dynamite fishing
  • Coral mining
  • Unsustainable tourism
  • Pollution
  • Eutrophication
  • Ocean dredging
  • Anchors
• 50% of wetland areas worldwide lost since 1900 as farming has intensified to feed populations
• Wetlands are also threatened by encroachment from tourism and development
• Climate change


  • Submerges or drowns wetlands e.g., mangroves
  • Destroys estuaries and floodplains through drought
• Arctic Tundra


  • Average temperatures between -5°C and -10°C
  • Long dark winters with temperatures below -20°C and high winds
  • Annual precipitation less than 150mm (Low)
  • Very short growing season - limited photosynthesis
  • Slow decomposition rates
  • Temperatures rarely rise above 10°C (low sun angle)