LZ lecture 6 Flashcards
What data is required for conservation of populations?
- Population size/density - Spatial distribution
- Ecological needs (ecological niche, including needs in terms of habitats, resources and interactions with other species; fundamental vs realized niche)
- Demographics (age/size distribution, sex ratio, etc.)
- Behavior
- Genetics
- Human pressures
Population viability analysis (PVA)
- A risk assessment process aimed to predict the likelihood that a population gets extinct or, rather, persists (i.e. its size stays above minimum viable population) under different environmental conditions
- Done to promote conservation efforts, identify conservation priorities (life stages, pressures, …), compare possible management actions, etc.
- Key info needed:
- Spectrum of ecological needs for the
population (ecological niche) - Life history stages of
maximum vulnerability - Demographic and environmental
parameters to create model
simulations
(at least 10 years to have a good
predictive power)
- Spectrum of ecological needs for the
PVA procedure
Construct a computer simulation that projects the size of the population into the future. Then for example:
- Select population growth rate for each time step at random from a distribution
or set of possible growth rates. This will result in ‘good years’ and ‘bad years’. - Repeat the projection (e.g., 1000 x ) to estimate what the population is likely to do on average.
Different modelling approaches
- Deterministic models
- Stochastic models
- Stochastic metapopulation models
- Individual based / spatially explicit models
Deterministic models
Mean values for demographic parameters
Stochastic models
Consider effects of environmental and demographic stochasticity
Stochastic metapopulation models
Include the spatial structure of:
- subpopulations
- habitat quality
- dispersion
Individual based / spatially explicit models
Each individual considered separately
Random demographic fluctuations
They can induce fluctuations in size in small populations
These fluctuations can be so stroing to lead to extinction (population size = zero) of local population
What does Vortex software simulate?
Vortex simulates individual-based simulation of deterministic forces, demographic, environmental, and genetic stochastic events on wildlife populations.
It can model extinction vortices threatening small populations.
What are the sequential events simulated by Vortex software?
Vortex simulates:
- mate selection
- reproduction
- mortality
- age increment
- dispersal
- removals
- supplementation
- truncation (if necessary to carrying capacity) iteratively to simulate the population dynamics.
What are sequential events?
Sequential events refer to a series of actions or occurrences that happen in a specific order, one after the other, with each event often depending on the outcome or occurrence of the previous one
Sensitivity analysis after a PVA
- To understand the sensitivity of PVA results to changes in the values of the model parameters
- When sufficient data for PVA are lacking, to identify which environmental and demographic parameters have the largest influence on the fate of a population
- Or which management actions (e.g. on habitat or population size) have the largest consequences
Theoretical and practical limits of PVA
- Often based on low quality data
- Density dependence often unknown
- Low confidence regarding the long term
Which species should we prioritize in conservation?
Priorities are needed to use funds efficiently
Priorities:
- Peculiarities (endemic species, rare species, genetically unique, ecological role, etc.)
- Risk (species with high risk of extinction)
- Usefulness (useful or potentially useful species to humans, commercially or in terms of other ecosystem services)
Example of conservation in situ: Reduce mortality (es. remove or mitigate fishing pressure, protect key life stages)
Population estimates are increasing
Threats to the Adriatic sturgeon
- Dams
- Pollution
- Overfishing
The Adraitic sturgeon (Acipenser naccarii)
