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15 Cards in this Set

  • Front
  • Back
Current extinction rates
- may be several thousand times higher than historical rates
- disproportional selection of older, taller and longer-lived organisms
-humans exploit resources at a fast rate
Determining when to take
Close to max - good for harvesting because the organism can't sustain or increase numbers

Close to zero - bad, potential Allee effects
Optimal harvesting time
- occurs at the point of maximum growth
Maximum sustainable yield (MSY)
-the point where population growth is at its maximum and ideal for take
- rates > MSY lead to a loss of organisms from natural processes (competition, predation) and density dependent effects
- rates < MSY could lead to a loss of too many individuals, Allee effects, interbreeding depression
Models for calculating yield
- max profit is a function of the population density and species longevity
- typically these models don't take spatial data into acount
-spatial distribution is important to understand the cost of harvest (How spread out is the target species)
effects of overexploitation
-can lead to a trophic cascade
-extinction
-loss of diversity
What is known about climate change?
- greenhouse gases are increasing
- average world temp is increasing
- sea level is rising
- temperature sensitive systems and processes have changed!
Greenhouse effect
sunlight penetrates and the light waves are transformed into infrared radiation
-radiation cannot escape and is reflected back to Earth
Basic Issues
- climate varies naturally but "climate change" refers to an additional, rapid change induced by humans
- increase several degrees C/century
- will disrupt the foundations of life on Earth
-ecosystems have evolved within a narrow band of climatic-environmental conditions
Indicators of climate change
- temperature
-climatic disasters: weather, hurricanes etc
ENSO events
- effect of climate change on the frequency and amplitude of El Nino events
- increased risk of drought and flood
Ecological impacts of climate change
-morphological changes will be required to deal with physiological changes - how quickly can species adapt?
- change in species composition
- shifts in species abundances and assemblages
- timing and phenology changes
- range shifts
*lots of uncertainty
implications of climate change
- extinctions: predictions of amount and severity varies
-increased disease
-spread of invasive species
- habitat loss
-changes in biotic interactions
conservation strategies and climate change
- species may move due to range and abiotic shifts but reserve boundaries won't shift
- boundaries will no longer protect species
Albedo effect
surfaces, like snow, reflect radiation back from the earth
- loss of snow leads to an increase in absorption of solar radiation