15 terms

Week 10: Biodiversity threats

Threats to biodiversity
Habitat loss, pollution, introduced species, over-exploitation, global change
Habitat loss
Tropical rain forests 16 mil km^2 -> 9 mil km^2
US prairie lost 97%
US wetlands lost 50%
Coastal CA wetlands lost 75-90%
Transformation to agricultural land, alteration of rainforest into palm oil plantation
Habitat fragmentation
Isolated patches don't have gene flow, increased species extinction
Edge effects
Causes reduction in habitat
Tropical rain forest canopy has no wind, dark, humid
Edge habitat has more wind, light, drier (new ecosystem of underbrush)
Atmosphere, soil, water toxins
Marine debris (plastics, abandoned fishing gear)
Biological magnification
Pesticides can move up food chain, accumulate and become more concentrated in higher trophic organisms
Excess nitrogen and phosphorus from nutrient pollution
Lead to algal blooms
Bacteria decompose algae and consume O2 -> dead zones
Invasive species
Species introduced to new areas via natural colonization or human transport (aesthetics, agriculture, hunting, species control, erosion control, accidental)
Compete with native species and may push to extinction
No predators/disease
Ballast water
Water pumped into boat to balance it out and prevent it from being too top heavy
240+ invasive species in SF bay due to this
Solutions: exchange at sea, UV treatment, chlorine/ozone
Over-exploitation (over-harvesting)
Hunting + poaching
Alaska salmon fishery
~80% of north American wild-caught salmon
Historically overfished -> regulated in 1960s, 1973 permit system, now well managed
Limited entry permits, limit fishing to only few days on each fishery, hatcheries release juvenile salmon to rivers
Farmed fisheries
Can lead to eutrophication from release of fish poop, bring new predators, increased disease, need more fish to feed farmed fish (carbon footprint)
Greenhouse effect
More greenhouse gas -> more heat retained
Dry places will get droughts, wet places will flood
Evidence of climate change
Increased global temperatures
Thinning/decreased sea ice (expansion of navigable routes in Arctic Sea)
Decreased snow + ice cap cover (decreases freshwater storage, increases heat retention)
Glacial retreat (increase sea level)
Sea level rise (result of glacier melt and thermal expansion)
Plant response to global warming
Range shift: American beech tree range will rise north as temperatures rise
Timing shift: mean annual temp increase correlates with mean date of first flower -> bad if flowers bloom before pollinators arrive