Habitat
Destruction
Habitat fragmentation
- roads, cities, farms,
etc.
- increased
influence of edges
- increased
predation and parasitism near edges
- some animals
require larger areas
Deforestation
- 75% of the
Earth's original forests have been cleared or severely disrupted - photo
- In USA, only 15% of original primary forest and just 1% of
tallgrass prairie remains
- US Forest
Service actually subsidizes timber industry by building logging roads at
taxpayer expense and selling trees for a fraction of their value
- Tropical
rainforests being cut or degraded at a rate
of 200,000 km2 per year. Currently about 50% left of historical
area covered.
Soil
Erosion
- Losses by both wind
and water when soil is exposed
- Can be caused
by clearcutting forests, overgrazing, not leaving riparian vegetation,
acid rain killing vegetation
- Taxpayers subsidized
grazing fees with $1.8 billion from 1985-1992
- Causes
sedimentation to accumulate in rivers and lakes
Desertification
Dams
- Loss of running water
- Accumulation of sediment
behind dams.
- Restricts sediments from
reaching the oceans where they are important in the rebuilding of beaches
that are eroded by waves.
- Restricts the passage of
species that require both salt and fresh water to complete their life
cycles, like salmon, river shrimp, some eels.
Draining wetlands
- have lost about 50%
of historical wetlands
- loss by state
Loss to urban
areas
Agriculture
- Very large areas covered
- Monoculture
- Herbicides - destroy nearby
vegetation as well as "weeds" in fields
