BCB 341: Principles of Conservation Biology

1. BCB 341: Principles of Conservation Biology Reserve and resource management Lecturer: James Reeler

2. Requires integration of a number of different concepts: • landscape ecology • ecosystem management • population genetics • disturbance ecology • At several different scales: • community • population • species • local • landscape In situ conservation

3. Minimum viable population size (MVP). • Based on two parameters: • acceptable probability of survival • time period being considered • Usually insufficient information to draw such conclusions • Smaller populations are more likely to go extinct over a given time period than larger ones • For a given set of parameters, the given MVP is highly species dependent. Small populations

4. Observed variance & MVP Persistence of bighorn sheep (Ovis canadensis) in California. b) Study by Wehausen (1999) MVP=50 • Study by Berger (1990) • MVP=100

5. Attempts to build models that predict future population trends • Depends on relationship between popn size (dependent) & weather, disease, landscape trends (independent) • Simplest model is stepwise: • where S = probability of individual surviving from t to t+1 • B = average number of offspring per individual • If these variable are measured in the field, the model can integrate randomly generated stochastic events • Variation in birth rate can be set by assigning variation level Population viability analysis

6. Monitoring is essential to the successful running of a reserve • Scale is important for monitoring • Up to 90% of species declines are missed due to inappropriate scale of monitoring • Level of monitoring for British butterlies was ~100km2 (10km x 10km) • Much larger than individual patch (habitat or population) size • As long as the species is detected within those cells, the population is not registered as disappearing, although it may experience huge reduction s within each area Measuring species Decline

7. Undetected species loss • 80-90% declines undetected in British butterflies (Cowleyet al., 1999) • Worst amongst widespread species,

8. Often small populations are disproportionally vulnerable due to genetic inbreeding • Franklin (1980) suggests a minimum of 50 individuals to proevent rapid loss of genetic variability • Studies on Drosophila suggest 500 as a minimum to allow for sufficient mutation to counter loss through genetic drift • Known as 50/500 rule for managing small populations • Complicated by difference between full population and the effective population (Ne) which is involved in exchange of genetic material • 3 common sources of deviation from perfect population Management of small populations

9. Variance in reproductive output • large variance means some genes are poorly represented in the filial generation • δ2= variance in family size • Unequal sex ratios • means some individuals cannot breed • with increasing inequality, Ne goes down • Population fluctuations • effectively causes generational bottlenecks that reduce gene numbers. Effective population

10. Until recently conservation management meant preventing all disturbance to natural areas. • Disturbance is not exclusively anthropogenic • Many areas require disturbance to maintain their biodiversity • Different reserves experience (and require) different disturbance regimes • Fynbos is a good example of a fire-disturbed ecosystem the requires regular disturbance • Savannah maintains the balance of trees and grassland through the interplay of several disturbance regimes: • fire • herbivory pressure (including migration) • elephants • drought/flood cycle • nutrient enrichment via animal excreta Disturbance ecology

11. Certain life cycle attributes denote plants (and some animals) that profit in a disturbance regime • short life cycle (from seed to flower) • allocation of most resources to reproduction • long-lived soil-stored seed banks • long-distance dispersal mechanisms • polymorphic seeds so that some are dispersed in time and some in space • disturbance-cued germination • adult plasticity, meaning that a plant can be big or small, slow or fast growing depending on the available resources in a patch • vegetative propagation (this adaptation is selected under the pressure of mammalian herbivores, shifting dune systems or floods. • These species REQUIRE disturbance over a certain period in order to maintain biodiversity Disturbance dependent species

12. Disturbance for biodiversity maintenance

13. Good knowledge of the required disturbance regimes of the conservation area is required (monitoring!) • For fynbos, burning every 13-15 years is recommended • Does not mean burn EVERYWHERE once every 15 years Disturbance regimes • Natural landscapes are a mosaic of different habitats, and different burn regimes • Older veld allows for reintroduction of species that may have been burned out • Young veld provides areas for succession to occur in natural processes • Record-keeping essential 6 17 1 9 3 4 3 15

14. After plants die, their nutrients are first consumed by detritivores before being returned to the soil. • During this period of mineral release, ecosystems are highly vulnerable. • Depending on rate of sprouting & repopulation compared with runoff & leaching, nutrients may be lost to the system or retained in new plants • Clearance of small blocks of vegetation tends to lose less nutrients (since they are taken up by the roots of surround plants). • Salts such as K, Mg & Na are lost first (highly soluble) although in arid environments they may form a salt crust that prevents seedling growth • Disturbance reducing a single species may cause cascade losses in other species (eg: rinderpest) • Hunting of elephants in central Africa • led to increased bush encroachment, and reduced savannah species. • reduction in poaching in conservation areas swung the balance the other way, with losses of some large trees and reduction in browsing species • increased poaching has led to reduction in grassland • each change caused large shifts in plant and insect diversity as well as large mammals Disturbance & Succession

15. Some wild populations are still harvested, and in certain reserve types (biosphere reserves) areas are set aside for limited take) • Central to the idea of harvesting is the concept of sustainable yield • This is any level of harvest that can be taken from the population indefinitely without detriment to the population • From a commercial point of view, the best amount to remove would be the maximum sustainable yield • Calculation of this is based on the carrying capacity of the land, and the logistic equation for population growth Sustainable harvesting

16. Sustainable harvesting Harvest exceeds growth; population declines to K/2 Harvest exceeds growth; population declines to extinction Growthexceeds harvest; population increases to K/2 Harvest exceeds growth; population declines to K/2 rK/4 a)Fixed quota method b) Fixed harvest effort method

17. Fixed harvest effort is a better method, but it still requires a good assessment of the carrying capacity for the species. • Assumes all individuals have equal reproductive potential, and hence does not take into account age structure of the population (in age-structured populations, MSY may be between 50 & 75% of K) • Assumes harvesting mortality is compensated by reduced natural mortality (no evidence) • Assumes no knock-on effects for interacting species (predators/competitors/prey) which may change carrying capacity of the environment • Ignores harvest rate of pre-reproductive individuals, body growth rate, etc. • This has led to development of more detailed models which describe biomass as a function of different processes (recruitment, natural mortality, etc) • Despite repeated efforts to achieve sustainable yield of Atlantic cod, stocks are still plummeting. Problems

18. Island biogeography & metapopulation biology influence reserve selection and management processes • Depend on relative rates of colonisation & extinction, which in turn depend on: • spatial distribution of patches • suitability of patches for reproduction • permeability of the space between patches • mobility of species • Shift away from conservation as self-regulating systems to dynamic non-equilibrial systems has led to integration of reserves into the broader landscape • Use a management hierarchy such as the biosphere concept • Utilisation of corridors (natural and manufactured • Integration of agricultural alternatives and communal wildlife management as a means of broadening the potential gene pool and land availability (Wine & Biodiversity initiative, Campfire) Landscape ecology

19. Ecosystem process is essential for population persistence, and so large scale conservation should aim to protect these systems. • Meyer (1997) nominated 7 principles for ecosystem conservation: • ecosystems are open, which should lead to a focus on conserving fluxes (flow) across ecosystem boundaries • ecosystems are temporally variable & bear the legacies of past disturbance • spatially heterogeneous on a variety of scales, which is vital for functionality • most effects in ecosystems are indirect, making knock-on effects unpredictable • component biological communities must be conserved to maintain ecosystem function • although several species may perform the same function in the ecosystem, they have different responses to biotic & abiotic environment (reduced variation in functionality in a changing environment) • humans are part of all ecosystems, and no ecosystems are unaffected by human activity. Ecosystem Function

20. How usefully a management policy integrates this holistic approach may depend on • how impacted an ecosystem is by human/economic activities, • how well we understand the processes • Meyer (1997) cites the example of the Knowles Valley (USA) which underwent extensive logging & roadbuilding in 1950-1985 • shifted sediment load from uplands to valley • decreased storage capacity in valley meant much was washed out of the catchment • degraded habitat for coho salmon, which had greatly reduced migration to the sea • By replanting trees & reducing sediment loss, a recovery programme stopped this. Ecosystem Function

21. Sometimes too much transformation has occurred, and it is necessary to allow short term, small scale losses to accommodate longer term restoration • Guiding principles for ecosystem management (Maltby, 1999): • management objectives are a matter of social choice • ecosystems must be managed in a human context • ecosystems must be managed within natural limits • change is inevitable • management & monitoring must occur at the appropriate scale, & use the full range of protected areas • needs to address global issues but act locally • must maintain ecosystem structure & functioning • should use appropriate scientific tools • follow the precautionary principle • needs a multidisciplinary approach. Ecosystem Function