BDC 332 ESS 333 Landscape Ecology and Conservation

BDC 332 ESS 333: Landscape Ecology and Conservation Planning RESERVE AND RESOURCE MANAGEMENT Lecturer: Rich Knight

IN SITU CONSERVATION q Requires integration of a number of different concepts: landscape ecology q ecosystem management q population genetics q disturbance ecology q q At several different scales: community q population q species q local q landscape q

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

OBSERVED VARIANCE & MVP 100 120 100 80 101+ 51 -100 60 31 -50 40 16 -30 1 -15 Persistence (%) 90 101+ 51 -100 80 31 -50 16 -30 70 1 -15 20 60 0 10 20 30 40 50 Time (years 60 70 a) Study by Berger (1990) MVP=100 10 20 30 Time (years) 40 50 b) Study by Wehausen (1999) MVP=50 Persistence of bighorn sheep (Ovis canadensis) in California.

POPULATION VIABILITY ANALYSIS q q q 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 q B = average number of offspring per individual q q q 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

MEASURING SPECIES DECLINE q q q 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 ~100 km 2 (10 km x 10 km) 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

UNDETECTED SPECIES LOSS q 80 -90% declines undetected in British butterflies (Cowley et al. , 1999) q Worst amongst widespread species,

MANAGEMENT OF SMALL POPULATIONS q q q 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

EFFECTIVE POPULATION Variance in reproductive output q large variance means some genes are poorly represented in the filial generation q q δ 2= variance in family size Unequal sex ratios means some individuals cannot breed q with increasing inequality, Ne goes down q Effective population size q 100 90 80 70 60 50 40 30 20 10 0 0 q 10 20 30 40 50 60 70 80 90 100 Number of females in population Population fluctuations q effectively causes generational bottlenecks that reduce gene numbers.

DISTURBANCE ECOLOGY q q q 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: q q q fire herbivory pressure (including migration) elephants drought/flood cycle nutrient enrichment via animal excreta

DISTURBANCE DEPENDENT SPECIES q Certain life cycle attributes denote plants (and some animals) that profit in a disturbance regime q q q q q 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

Biodiversity DISTURBANCE FOR BIODIVERSITY MAINTENANCE Time since disturbance Increasing disturbance

DISTURBANCE REGIMES q q q q 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 Natural landscapes are a 1 mosaic of different habitats, and different burn regimes 17 3 6 Older veld allows for reintroduction of species that may have been burned out 9 Young veld provides areas for 3 succession to occur in natural 4 processes 15 Record-keeping essential

DISTURBANCE & SUCCESSION q q q q 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 q q 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

SUSTAINABLE HARVESTING q q q 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 Growthexceeds Harvest exceeds harvest; growth; population increases declinesto to. K/2 extinction Harvest exceeds growth; population declines to K/2 d. N/dt r. K/4 0 K/2 Population size (N) a)Fixed method b) Fixed quota harvest effort method K

PROBLEMS q q q q 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 agestructured 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.

LANDSCAPE ECOLOGY q q Island biogeography & metapopulation biology influence reserve selection and management processes Depend on relative rates of colonisation & extinction, which in turn depend on: q q q q 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)

ECOSYSTEM FUNCTION q q 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: q q q q 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 q How usefully a management policy integrates this holistic approach may depend on how impacted an ecosystem is by human/economic activities, q how well we understand the processes q q 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 q decreased storage capacity in valley meant much washed out of the catchment q degraded habitat for coho salmon, which had greatly reduced migration to the sea q By replanting trees & reducing sediment loss, a recovery programme stopped this. q

ECOSYSTEM FUNCTION q q 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): q q q q q 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.