5.4 Forest ecosystems and deforestation

Natural and planted forests occupy about 31% of the earth's land

Russia, Brazil, Canada, The United States and China have the largest forest areas

Forests Provide human with various resources:

Biofuel: Wood for burning- Cooking and heating
Industrial wood: Wood for construction and paper
Medicines: Traditional medicines that come from forest plants are used 80% by humans

  • Ecosystem services essential for human survival and health
  • Ecosystem services essential for economies

Scientists divide forests into major types based on their age and structure

  1. Old growth / Primary forest
  2. Second growth forest
  3. Tree plantation / tree farm / commercial farm

Old growth / primary forest: an uncut or regrown forest that has not been seriously disturbed by human activities or natural disasters for 200 years or more. Are reservoirs of biodiversity because they provide ecological niches for a multitude of wildlife species

Second growth forest: a younger stand of trees resulting from secondary ecological succession. Develop after the trees in an area have been removed either by human activities, such as clear-cutting for timber or conversion to cropland, or by natural forces such as fire or hurricanes

Deforestation: the temporary or permanent removal large expenses of forest for agriculture, settlements, other uses

Surveys by theWorld Resources Institute (WRI) indicate that during the 8,000 years, deforastion has eliminates almost ha of earth's growth forest cover. Most current forest losses are concentrated in less-developed countries, especially in tropical areas

Problems caused by deforestation:

  • Water pollution and soil degradation from erosion - Acceleration of flooding
  • Local extinction of specialist species
  • Habitat loss for native and migrating species
  • Release of CO2 and loss of CO2 absorption
  • Reducing tree cover allows moisture in air and soil to evaporate and be blown away
  • Changes local time
    Soil becomes exposed and dry
  • Forests may never be able to grow back again, and instead only savannahs or grasslands can exist there.

Fragmentation = When a large, intact area of habitat such as a forest or natural grassland is divided intro smaller, isolated patches or habitat islands
Causes: habitat destruction and roads between those areas

Edge effects: Conditions at the edge of a habitat are usually different to the core zone, making it unsuitable for the organisms that liven the core biome

Tropical forests are essential to the planet. The cover about 6% of the earth's land area

  1. Tropical forests absorb and store about one third of the world's terrestrial carbon emissions as part of the carbon cycle
  2. More than half of the world's known species of terrestrial plants, animals, and insects live in tropical forests

500,000 football fields of tropical forest are destroyed every week

Examples: Indonesia: Third largest tropical forest in the world

  • World's highest rate of deforestation: 98% could be gone y 2021

Forest forest are increasing in frequency and severity

Surface fires: usually only burn undergrowth and leaf litter

  • Mot mature trees survive
  • Most wild animals escape
  • Can be essential in som ecosystems

Crown fires: are large hot fires that leap from treat to treetop

  • Destroy forest areas completely
  • Often occur if smaller fires haven't happen in recent years, allowing leaf litter to accumulate

Forest fires are normal by they are getting worse Forest fires occur in many areas due to dry storms - lightning hits the ground and ignites fry leaf littler/twigs etc.

Reasons for increase of fires:

  • Climate change: Increase in temp= longer drier summers
  • Residential expansion into forest areas = irresponsible human activity
  • Suppression of smaller fires = accumulation of leaf litter
  • Fragmentation = forest edges exposed to wind and the sun = drier

Climate change and human activity is responsible for invasive species of vegetation and animals

  1. Climate change is a direct threat to forests, change in temperature and humidity prevents local plants and trees from thriving
  2. Invasive plants from warmer climates may outcompete local species
  3. May absorbing new animals, especially insects, that may feed on plants or trees