Download Deforestation - University of South Alabama

Deforestation
• Transform an area from forested to nonforested
– Logging
– Land clearing
• Urban
• Agricultural
• Mining
Old growth forests
• Multi-aged forest with large, very old trees
(100+ years), younger trees (although
generally not very young), fallen timber,
and underbrush.
• Forest regenerated after disturbance (fire,
logging) is generally called second-growth
until it has again acquired old-growth
characteristics
• Old growth forests are desirable to loggers
because of the size of logs and tree
species
– Logging old growth forests very contentious
– Old growth forests home to rare, threatened
and endangered species: Northern Spotted Owl
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Disruptions
in a biome/ecosystem
• Corridors and patches: a
break or cut in an area,
does not contain the
normal type of vegetation
• Species may need a
continuous cover of
fauna to live
Deforestation
• Tree removal reduces the production of oxygen
released into the atmosphere
• Also releases carbon into the atmosphere (as
carbon dioxide or methane)
• Logging or land clearing often involves burning
an area – also release CO2
• Disturbs the habitat and ecosystem
Logging
• In US, old growth forests logged in 1800s
and early 1900s
• Trees cut and land left to recover on its own
– "cut-out and get-out" philosophy
• Traditional logging very invasive and
destructive on the land
– Access roads compact soil
– Refuse piles
– Soil erosion
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Logging
Clear cutting
• All trees removed in an area
• Creates a patchwork effect
• Meant to save some areas for animal habitat
while harvesting the wood
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Clear cutting
• May be good for some tree species that
need sunlight to grow
• All new trees in area now same age and
same species
– Increased susceptibility to disease, fire and
insects
• Increased erosion and flooding
• Loss of nutrients
Low-impact logging
• Also called “reduced-impact”, “sustainable”
or “gentle logging”
• Take some of the trees – leaves some
trees
• Methods differ but usually seek to:
– Minimize damage to the residual stand
– Minimize impact to land
– Minimize erosion
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Low-impact logging
• Selective cutting of trees – age and
location
– Maintains diverse forest for resident flora and
fauna
– Resists disease and fire
– Reduces erosion
• Smaller scale equipment
US Logging
• Private and public (USFS) lands
– Private lands – may have old-growth forests or
tree farms
• Harvesting methods differ
• After harvested, area replanted
– Public lands – a lot more old-growth forests
• Very cheap for forest companies to log on public
lands
• Government sells logging rights very cheaply
• Land then replanted – typically clear cut
Post-logging: tree farms
• Privately owned managed
forest used for timber
production
• Actively started in 1940’s
– Fears of a “timber famine”
– Trees were being cut at an
unsustainable rate
• Movement away from the
"cut-out and get-out"
philosophy
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Post-logging: tree farms
• First official tree farm in Washington state
• Today – very productive
– California has 600+ tree farms
– Can have tree farms for specific species
– Not just for Christmas trees
• Idea is to have several stands of different
ages so harvesting is staggered
– Can, in some instances, just plant and walk away
for several years
Tree farm drawbacks
• Not natural
– Usually only 1 species – limits fauna
– Susceptible to disease and fire
• Better than harvesting old-growth forests
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Deforestation in other parts of
developed world
• Most of Europe no longer has any oldgrowth forest
• Tree farming extensive and well-managed
• Japan – wood shortage
• Canada – extensive logging of old-growth
forests
Tropical rainforest clearing
• Approximately 1% of
tropical rainforest lost
each year
– Logging
• Some regeneration now
– Agricultural
• Crops: coffee, bananas,
rubber trees
• Pasture: cattle
• Central America – ½
rainforest remains
Rainforest clearing
• Soil quality quickly
diminishes
• Road construction to
access logging sites
opens area up to
occupation
• Loss of species
tremendous
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