1.6 Deforestation and Ecological Succession

deforestation

  • deforestation: the destruction of forests
    • humans alter, fragment, and eliminate forests
  • common causes of deforestation
    • convert the land for agricultural use (eg. cattle, crops)
    • form new settlements as population grows
    • logging for lumber and firewood
    • ~2 billion people currently rely on firewood for cooking and heating, though cooking on an open fire is dangerous and inefficient, releasing carbon monoxide and CO2 into the atmosphere
    • extraction of minerals
    • increasing forest fires due to climate change
    • slash-and-burn agriculture
    • trees are cut down, allowed to dry, and burned to make the soil nutrient-rich, and making the land available for crops or cattle
    • may be a form of subsistence agriculture (farm for self-subsistence)

slowing or stopping deforestation

effects of deforestation

  • loss of cover exposes the forest floor (erosion)
  • as less CO2 is captured, more is released into the atmosphere (climate change)
  • less waste recycling, water purification, and pollution control
  • loss of biodiversity
  • loss of language and cultural/religious practices (cultural extinction)

guiding principle: sustainability

  • sustainability: the principle of meeting present-day needs without compromising the ability of future generations to meet their needs
  • maximum sustainable yield: the act of acquiring the maximum amount of a resource (eg. wood) without depleting the resource
  • ecological pricing: the idea that the costs of the goods we use should take into account their environmental costs
    • putting a price on nature
    • protecting/creating forest land is the process of setting aside public land to grow trees
  • national forests are multi-use lands with an emphasis on balancing recreation, grazing, timber, watershed protection, wildlife and fish, and wilderness
    • national forests are not national parks

debt for nature swaps

  • many biodiversity hotspots are located in developing countries, which usually have large foreign debt
  • debt-for-nature swap: an agreement between a country and its debtor(s) in which part of the country’s debt is forgiven in exchange for a commitment to protect part of its land \n

land reforms

  • land reform: a policy to reach more equitable ownership of an area of land \n

individual actions

  • reduce/reuse/recycle
  • conserve wood and buy products made from sustainably harvested wood
  • buy non-timber forest products like Brazil nuts
  • leave nonexistent or small footprints if spending time in forests

ecological succession

ecological succession

  • the types of species present in a community are usually changing in response to environmental conditions
  • ecological succession: the process of gradual change in the composition and function of a community

primary succession: the community is developing in a site previously unoccupied by living organisms, a barren habitat with very little topsoil

  • pioneer species → intermediate species → climax community
    • process of primary succession
    • eg. lichens are pioneer species and contribute to the formation of the soil
  • soil formation: biological factors interact with physical and chemical factors to develop the soil
    • one such biological factor is lichens

secondary succession: begins in an area where natural vegetation has been disturbed, but soil remains

  • eg. abandoned farmland, cut forest

types of forests

  • primary forest/old-growth forest: a forest that has not been disturbed for an extended period of time (200+ years)
    • usually uneven-aged — trees of different ages and heights
    • have many different species, few invasive species
  • secondary forest: a forest that has regrown after some human disturbance, results of secondary succession
    • may be even-aged, if all trees were planted at the same time
    • may lack very old and very tall trees
    • usually have less species diversity
  • tree plantation/tree farm: an area of trees managed by humans, only containing one or very few species that are commercially valuable (monoculture forestry)
    • usually even-aged
    • placed in regular rows

global distribution of forests

  • 70% ⇒ secondary growth
  • 25% ⇒ primary growth
  • 5% ⇒ tree plantations

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