Topic 11: Population Ecology (continued) Flashcards
What 2 fields apply population ecology?
- Bioeconomics. Managing exploited populations.
- Conservation. Conserving endangered or threatened populations.
What is the largest harvesting rate that can be maintained indefinitely?
The Maximum Sustaining Yield (MSY)
When is the MSY applied?
When the rate of harvest is less than the rate at which the population can grow.
What are two outcomes of Maximum Sustainable Yield (MSY) harvesting?
- If the population is growing rapidly, we can harvest, and the population will replace itself rapidly.
- If the population growth is low, harvesting risks the population not being able to replace itself and crashing.
When does population growth = 0?
When population is at 0 or K (carrying capacity).
What is the population numbers (N) at maximum growth rate?
N = 1/2 K (carrying capacity)
What are 2 ecological problems with harvesting at MSY?
- Biological parameters are often not well known. MSY assumes that population growth rate is known
- Environmental fluctuations mean that carrying capacity is not constant.
When will a MSY population decline?
If harvest > population growth rate
How is MSY obtained?
By harvesting at maximum growth rate while maintaining 1/2 K
What are 3 economic problems with MSY?
- Fluctuations in K will impact quotas and incomes for harvesters.
- There is greater short-term gain by overharvesting.
- The tragedy of the commons. If one harvester does not exploit the resource, it is likely that another will.
What is the wisest harvest rates?
Below MSY
What is Minimal Viable Population Size (MVP)?
The population size above which a species must be maintained to ensure its long-term survival.
What is an example of ‘no population size can guarantee persistence of a species indefinitely’?
Passenger Pigeons in North America
What must be determined for MVP estimation?
An acceptable probability of extinction over fixed time intervals.
e.g. 2% over 1000 years, 1% over 100 years
Is there a single MVP to apply to all species under all circumstances?
No.
What 2 broad factors determine the likelihood of extinction?
- Deterministic factors.
- Stochastic (chance) processes.
What does MVP of a species depend on?
- Ecological characteristics of a species. e.g. longevity, birth and death rates, dispersal
- Environmental conditions.
What are deterministic processes?
Ongoing processes with relatively predictable consequences.
e.g logging forests removes the largest and oldest trees, so it can be predicted that there will be fewer large old trees available for habitats
What are stochastic processes?
Processes that happen by chance and have an outcome that is difficult to predict.
Variations in processes have a large effect on what populations?
On small populations.
Chance variations in processes can affect population structure and capacity for population growth.
What are the 4 types of stochastic processes?
- Genetic. loss of genetic diversity including inbreeding and genetic drift
- Demographic. e.g. sex ratio, birth rates
- Environmental. e.g. change in climate, food available, or predator numbers
- Catastrophic. e.g. fire, flood and drought
What is population viability analysis?
The species-specific risk assessment of the probability of extinction within a specific time frame.
