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5.4 Forest ecosystems and deforestation (Natural and planted forests…
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
Old growth / Primary forest
Second growth forest
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
Tropical forests absorb and store about one third of the world's terrestrial carbon emissions as part of the carbon cycle
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
Climate change is a direct threat to forests, change in temperature and humidity prevents local plants and trees from thriving
Invasive plants from warmer climates may outcompete local species
May absorbing new animals, especially insects, that may feed on plants or trees