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DOMINANT AND EMERGING PARADIGMS IN CONSERVATION ECOLOGY The meaning of "paradigm" as a scientific "world view" How and why paradigms change Dominant paradigms of previous decades An old and enduring question: "What controls population dynamics?" 1. Population dynamics driven by the environment, especially weather • Thrips, roses, weather • Popular in Europe and Australia • Emphasizes stochastic (chance) over deterministic, not directly densitydependent • Useful in degree-day models for biological control Thrip damage on roses Severe winters increase mortality of deer but increase survival of grizzly bear and wolf young thrips 2. Population dynamics driven by competition • Common idea in New World • Influence of Darwin and Hutchinson • Fundamental vs realized niche gave rise to idea of community matrix and field tests • Deterministic generally but stochastic processes can be important African grazing animals: Competition can have strong temporal component Plants frequently compete for nitrogen in temperate zone and phosphorus in tropics 3. Population dynamics driven by predator x prey • Wildlife management • Early interest from presumed conflict with human hunters; livestock death • Ideas: search-handling, prey dispersal, predator satiation, prey refugia • Keystone predator, competition, diversity • Deterministic and stochastic Starfish as keystone predators may reduce competition from mussels and enhance biodiversity. Crown of thorns starfish may reach large numbers and reduce coral biodiversity. Genetics and behavior Refugia for prey Large area required Predators can be prey The other old and enduring question, "Why are there so many species?" Evolutionary Versus Ecological time Biodiversity in evolutionary time • Biogeography (ancient legacies) • Stable environments facilitate narrow niches, hence more species packing (rainforests and deep ocean??) • Speciation following dispersal barriers • Speciation following major extinctions Biodiversity cycles over geological time. Rainforest diversity ?? Deep ocean vents have rich diversity Biodiversity in ecological time • Environments that are both highly productive and heterogeneous have high biodiversity (not always) • Stable competitive environments should have fewer species due to displacement (note contrast with speciation) • Highly variable environments dominated by colonizing species, diversity low Emerging Paradigms • New emphasis on spatial and temporal scale-dependent processes • Coupling population dynamics with ecosystem analyses Metapopulation of mountain lions in So California. Some are sinks (e.g.,Laguna) • Stability at the large scale is dependent on non-stability processes acting at smaller scales • Coupling bottom-up with top-down processes (forest example) • Communities are comprised of a mix of weakly and strongly interacting species (esp. protect keystone species/resources) • Stability at the large scale is dependent on non-stability processes acting at smaller scales (forest example) • Coupling bottom-up with top-down processes (forest example) • Communities are comprised of a mix of weakly and strongly interacting species (esp. protect keystone species/resources; sometimes conflicts with people, sometimes stewardship) Forest canopy looks homogeneous and stable at this scale Spatial heterogeneity is evident from digitized image (left) and very evident from enhanced spectral imagery (below) At a smaller scale you may pick out particular causes of spatial heterogeneity. Pine bark beetles kill trees (left) which eventually result in forest patches of different ages (below) At the smallest scale critically important processes of nutrient uptake take place that influence productivity and additional spatial heterogeneity. To understand forest structure and change you need to understand top-down processes (disease, fire, beetles) and bottom-up processes (nutrient uptake). Spatial and temporal scales are very different. • Ecosystems are open so landscape scale is important (from small ponds to “dead zones” • Ecosystems have characteristic disturbance regimes (complicated by changing environment) • Rare episodic events can leave legacy (Mt St Helen eruption) • Legacies generally important (pig and cattle drive example) Intermediate Disturbance Hypothesis originated with Connell’s observation of tree falls in Australian rainforests. Frequency distribution of gaps created by tree falls gave rise to the Intermediate Disturbance Hypothesis…important in forest management Boulders of different sizes (=different stability) used to test Intermediate Disturbance Hypothesis Disturbance patches may be small, as in this leafcutter ant colony. Or very large. This is Mt. Saint Helens, 1970, pre-eruption Mt. Saint Helens after the 1980 eruption Disturbances have a natural history and a legacy of effects. Time of eruption in spring was important. Many small animals survived in pocket gopher burrows. Seeds of many plants were stored in marmot burrows. Hurricane Dean Monday afternoon…heading towards the Sian Kaan reserve as a category 5 storm. Dean’s path over the ocean leaves cool and nutrient-rich waters. H. Dean cat. 4 skirts the south coast of Jamaica H. Dean and house destruction in Kingston, Jamaica Sian Kaan Biosphere Reserve. About 30 miles north of the eyewall of H Dean. This is the zone of greatest wind and ocean surge forces. Indigenous maya living in the Sian Kaan Biosphere Reserve harvest conch and spiny lobster on a sustainable schedule. Spiny lobster Why H Dean did little damage to Sian Kaan….mangroves absorb the storm energy Typical dense stand of mangroves along estuary Mangroves protecting the Sian Kaan lagoon where conch and lobster are harvested. The mangroves provide a critical “environmental service”…a rapidly emerging paradigm or focus in conservation biology. Mangroves destroyed to make a shrimp pond. An economically and environmentally important ecosystem (environmental service) is replaced by a short-term economic activity. Shrimp ponds in mangroves are often druglaundering operations. Shrimp ponds can be sustainably operated in mangrove regions if they are located on mudflats. Finding the appropriate economic and environmental value of ecosystems as environmental services is a major focus of conservation. • • • • Watersheds Riparian forests Salt marshes Many other examples Ecosystem Services People are both players and stakeholders in conservation initiatives and ecosystem processes in general. Recognizing and measuring “Ecosystem Services” (natural and economic value of the environment) is an increasingly important goal for conservation ecologists. Decline of pollinators represents loss of a major environmental service. Why are pollinators declining so rapidly??? 36% of honeybee hives lost 2007. Native bee decline?? Disease (several exotic) Chemicals to control varroa mites make honeybees susceptible to disease Pollutants Future…Climate change uncouples flower phenology from bee emergence. Many scientists now believe that disease is an important component in shaping populations and communities Domestic cats are hosts for toxoplasmosis. Lethal to sea otters and of increasing concern for humans (zoonotic). Avian malaria especially serious for island populations that lack resistance. Mosquito vector feeding on Hawaiian Honeycreeper. But like other themes in conservation, disease is also investigated in a larger environmental context. Mystery of lion population crashes African buffalo are not usually bothered by tick fever. When stressed by drought the buffalo become heavily tick infested and weakened by tick fever. When lions feed on weakened buffalo they get tick fever, usually not fatal. Lions weakened by tick fever are highly susceptible to canine distemper. Canine distemper virus Rhodesian lion dog Drought weakens buffalo making them susceptible to tick fever. Lions get tick fever by eating sick buffalo. Weakened lions die from canine distemper. So….agricultural demand for water coupled with climate change create more frequent droughts. More farmers mean more farm dogs and higher risk of canine distemper transfer to lions. Population crashes of lions results from this complex interaction. But don’t conservationists mainly focus on endangered species? • Many do but their approaches are changing to include larger scales. • Some examples -riparian plants and ice scour -grizzly bears and whitebark pine rust -Dickcissel bird and Colombia rice pests -darters and parking lots Paradigm-summary • Old paradigm, “What controls population dynamics?” • A) Environment-stochastic • B) Competition-deterministic • C) Predators-significance of refugia, affect competition, keystone species Summary • The other enduring paradigm, “Why are there so many species?” • A) Evolutionary time, biogeography, extinctionspeciation cycles, stable environments (species packing) • B) Ecological time, high productivity plus spatial heterogeneity, highly stable and highly variable environments often have fewer species. Summary • Emerging paradigms focus on nonequilibrium processes, especially disturbance regimes • Conservation management emphasizes maintaining appropriate disturbance regimes • Disturbances have important natural histories and legacy effects Summary • Resiliency to disturbance and concern over environmental degradation led to idea of ecosystems providing environmental services Summary • Important emphasis on processes that are coupled and occurring at different spatial and temporal scales (metapopulation structure and forest examples, ecology of disease, dead zones, etc etc)