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)
Conservation strategies are typically divided in..
In situ:
- Conservation of species in their natural habitat
- Including e.g. in natural reserves or MPAs
Ex situ:
- Conserving species outside of their natural habitat
- E.g. aquaria, zoos, botanical gardens, seed banks
They are not mutually exclusive!
In situ conservation
At the single species level, we can act removing or reducing the major factors that have a major impact on population dynamics (input from PVA and sensitivity analysis).
For instance:
- Reduce mortality (es. remove or mitigate fishing pressure, protect key life stages, remove predators)
- Increase population size (restocking, traslocation, reintroduction)
Example of conservation in situ: Reduce mortality (es. remove or mitigate fishing pressure, protect key life stages)
Population estimates are increasing
Conservation in situ: Increase population size (restocking, translocation, reintroduction)
This is more common in terrestrial and freshwater species, but there are some marine examples:
- Corals
- Seaweeds
- Seagrasses
(See papers on moodle)
Specific examples of conservation in situ: increase population size
- orphans rearing in sea otters
- introducing Homarus homarus (lobster) juveniles
- introducing Acipenser naccarii (Adriatic sturgeon) juveniles
Threats to the Adriatic sturgeon
- Dams
- Pollution
- Overfishing
The Adraitic sturgeon (Acipenser naccarii)
Strong decline, indicated by catch records
- 2000 Kg/year at the beginning of the 1970s
- About 200 Kg/year in 1990 and 1991
- Only 19 specimens were caught in 1993
Adriatic sturgeon farming
- 1977: initial farming of wild Adriatic sturgeons (ABOUT 90 INDIVIDUALS)
50 survived up to maturity - 1988: first successful reproduction
- 1991: first restocking / reintroduction program
- Present stock: less than 10 animals of wild origin.
Advantages in situ conservation
- The species will be protected/restored in its own habitat, and so e.g. it will have all the resources that it is adapted too
- The species will continue to adapt/evolve in their environment, without artificial disturbance
- The species have more space for moving
- Breeding is easier
- It is cheaper to keep (and protect) an organism in its natural habitat
Disadvantages of in situ
- It is difficult to control illegal exploitation (e.g. poaching or illegal fishery)
- The environment may also need restoration and alien species are difficult to control
Ex situ conservation
- Aimed at restoring self sufficient populations in nature once enough individuals and the right environmental conditions are present
- Strictly coupled to in situ conservation (e.g. with periodical releases to support/increase wild populations)
- Certainly not ideal but sometimes the best and only solution left for the very highly endangered species
Advantages ex situ
- Individuals can be closely monitored and assisted if needed
- You can obtain a lot of info on species
- Reduced need to capture wild individuals for research/education (and aquaria through education can promote to conservation)
Disadvantages ex situ
- Doesn’t work for all species
- Unsustainable for all species
- Focus only on charismatic species
- Costs can be high (comparison to in situ conservation)
- All problems associated with small sized populations (high extinction risks, inbreeding, etc.; ethical problems)
In any case, what is the best way to protect biodiversity?
The most efficient and sustainable approach is to protect habitats, communities and ecosystems
