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5.4 forest ecosystems and deforestation (habitat fragmentation (results…
5.4 forest ecosystems and deforestation
forest ecosystems
natural
planted
cover 31% of earth
Russia
Brazil
canada
USA
china
resources
biofuel
indusrial wood
meds
economic services
fuelwood
lumber
pulp to make paper
mining
livestockgrazing
recreation
jobs
oxygen
ecosystem services
support energy and chem cycle
reduce soil erosio
absorb and release water
purify water/air
influence local and regional climate
store atmospheric carbon
provide numerous wildlife habitat
forest structure (age,vegetation, type, size, shape)
old growth/primary forest
not been disturbed by humans for >200yrs
reservoirs for biodiversity bcz of eco niches for many species
2nd growth forest
younger trees from 2nd eco succession
after trees have been removed(human or disaster)
tree plantation/tree farm/commercial farm
deforestation
temporary/permanent removal or many forests for agriculture, sediments, etc
past 8k yrs humans have taken half of old forests(1950-)
northern boreal forests (Alaska, Canada, Scandinavia, Russia):1/4 of forest area of earth
problems
water pollution
soil degradation from erosion
acceleration of flooding
local extinction of specialist species (extirpation)
habitat loss for native and migrating species
release of CO2 and loss of CO2 absorption
biome change
decrease in tree coverage lets air moisture and soil to evaporate
change local climte
soil is exposed and dry (droughts)
forests may never grow back=deserts
forest tree harvesting (clear cutting)
complet destruction of habitat=biodiversity loss
soil erosion
sediment pollution of waterways
reduced atmospheric CO2 uptake
fast and cheapest way
habitat fragmentation
large virgin area is divided into habitat islands
as bad as destruction for large species
roads
results
reduced forest tree cover
blocked animal migration route
population is divided into small groups
consequences
prevents migration, gene flow
each group is vulnerable, competition, disease, disasters
increases exponentially
edge effect
conditions at edge of habitat are diff from core, becomes unsuitable for life
tropical forest deforestation
cover 6% of earth land
absorb 1/3 of world's terrestrial
more than half of known land plants, animals, and insects live in tropical forests
vulnerable to extinction if habitat is disturbed, cz of specialized niches
reduces carbon absorption and causes climate change
accounting 10-15% of greenhouse emissions
Amazon
40% of remaining tropical forest
20% has been removed (for cattle raising)
mining, biofuels, soybean
Indonesia
3rd largest tropical forest
highest deforestation rate
palm oil plantations
Africa
wood for fuel
clearing plots for farming
forest fires
naturally
lighting
dry storms
surface fires
only burn undergrowth leaf litter
mature trees survive
wild animals escape
essential (sometimes)
clears dry bush away, prevents large fires
liberates nutrients from decomposing litter
stimulates germination of species
crown fires
large from treetop to treetop
destroy areas completely
if small fires havent happened, letting leaf litter grow
rzns
climate change
residential expansions (humans)
irresponsible human activity
suppression fo smaller fires
fragmentation
invasive species
climate change
threat to frests
change in temp&humidity prevents plants from growing
invasive plants outnumber locals
new animals that become pests
human activity