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)

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

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

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

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