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Transcript
Biodiversity Defined • “Biodiversity is the total variety of life on earth. It includes all genes, species and ecosystems and the ecological processes of which they are a part” (Convention on Biodiversity, 1992) Central Case: Saving the Siberian tiger • The largest cat in the world • The Russian Far East mountains house the last remaining tigers • Nearly became extinct due to hunting, poaching and habitat destruction • International conservation groups saved the species from extinction – Research, education, zoos, and captive breeding programs Where is the biodiversity? • Endemic species – restricted to a small region – isolated areas (islands, mountain ranges) – product of unique habitat, climate features Biodiversity hotspots - areas with a high concentration of endemic species, experiencing rapid habitat loss Species diversity • Species Diversity = the number or variety of species in the world or in a particular region – Richness = the number of species – Evenness or relative abundance = extent to which numbers of individuals of different species are equal or skewed – Speciation generates new species and adds to species richness – Extinction reduces species richness The taxonomy of species • Taxonomists = scientists who classify species – Physical appearance and genetics determines a species – Genera = related species are grouped together – Families = groups of genera • Every species has a twopart scientific name: genus and species Subspecies: the level below a species • Subspecies = populations of species that occur in different areas and differ slightly from each other – Divergence stops short of separating the species – Subspecies are denoted with a third part of the scientific name Bengal tiger = Panthera tigris tigris Siberian tiger = Panthera tigris altaica Genetic diversity • Encompasses the differences in DNA among individuals within species and populations • The raw material for adaptation to local conditions Genetic diversity • Populations with higher genetic diversity can survive – They can cope with environmental change • Populations with low genetic diversity are vulnerable – To environmental change – Disease – Inbreeding depression = genetically similar parents mate and produce inferior offspring Ecosystem diversity • Ecosystem diversity = the number and variety of ecosystems • Also encompasses differing communities and habitats • Rapid vegetation change and varying landscapes within an ecosystem promote higher levels of biodiversity Some groups contain more species than others • Species are not evenly distributed among taxonomic groups – Insects predominate over all other life-forms – 40% of all insects are beetles • Groups accumulate species by – Adaptive radiation – Allopatric speciation – Low rates of extinction Insects outnumber all other species Measuring biodiversity is not easy • Out of the estimated 3 - 100 million species on Earth, only 1.7 - 2 million species have been successfully catalogued • Very difficult to identify species – Many remote spots on Earth remain unexplored – Small organisms are easily overlooked – Many species look identical until thoroughly examined • Entomologist Terry Erwin found 163 beetle species specialized on one tree species Biodiversity losses and species extinction • Extinction = occurs when the last member of a species dies and the species ceases to exist • Extirpation = the disappearance of a particular population from a given area, but not the entire species globally – Can lead to extinction Extinction is a natural process • Paleontologists estimate 99% of all species that ever lived are now extinct • Background rate of extinction = natural extinctions for a variety of reasons – 1 extinction per 1 to 10 million species for mammals and marine species – 1 species out of 1,000 mammal and marine species would go extinct every 1,000 to 10,000 years Earth has experienced five mass extinctions • In the past 440 million years, mass extinctions have eliminated at least 50% of all species • After every mass extinction the biodiversity returned to or exceeded its original state Current Status of Biodiversity • 1.4 million described species, possibly 10 million in total • Background extinction rate – rate of species loss in the absence of human activities – fossil record: species survive 1-10 million years – one year: one species has a 1 in 1-10 million chance of going extinct – total: 1 extinction per year The current mass extinction is human caused • During this Quaternary period, we may lose more than half of all species – Hundreds of human-induced species extinctions, and multitudes of others, teeter on the brink of extinction • The current global extinction rate is 100 to 1,000 times greater than the background rate – This rate will increase tenfold in future decades due to human population growth and resource consumption People have hunted species to extinction for millennia Extinctions followed human arrival on islands and continents Current extinction rates are higher than normal • The Red List = an updated list of species facing high risks of extinctions – 23% of mammal species – 12% of bird species – 31 - 86% of all other species • Since 1970, 58 fish species, 9 bird species, and 1 mammal species has gone extinct – In the U.S., in the last 500 years, 236 animal and 17 plant species are confirmed extinct – Actual numbers are undoubtedly higher Biodiversity loss has many causes • Reasons for biodiversity losses are multifaceted, complex, and hard to determine – Factors may interact synergistically • Four primary causes of population decline are: – – – – Habitat alteration Invasive species Pollution Overharvesting • Global climate change now is the fifth cause Ecological interactions Biodiversity is more than the sum of the parts Interactions “structure” communities, maintain diversity, and make ecosystems work e.g. Competition Predation Mutualisms (e.g. pollination, seed dispersal) • Some estimates for current rate: – 1 species per hour – 1 million species total, so far – 10% of all species so far – 8.8% of all species – 27,000 species per year – 20% of neotropical plant species – 100 to 10,000 times the background rate • Numbers of threatened/endangered species: – 5,188 vertebrates (9%) – 1,992 invertebrates (0.17%) – 8,321 plants (2.89%) – 2 lichens (0.02%) • Since 1600, ~1000 species have gone extinct (probably many more) Why do species go extinct? 2 separate processes: 1. Something causes a large population to decline. 2. Small populations go extinct. Causes of species declines 1. Habitat destruction and fragmentation 2. Introduced species 3. Exploitation and overharvesting 4. Pollution 5. Climate change Conservation biology • Concerned with loss of biodiversity, not just loss of species – “Fundamental loss of resources in genetics, species, community attributes and ecosystem properties” – Flip side: maintenance of biodiversity, ecological and evolutionary processes Why care about biodiversity? • Intrinsic value (Muir, 1838-1914) – All species have value independently of their utility to humans • Utilitarian value (Pinchot, 1865-1946) – Species that provide the “greatest good to the greatest number” (over the longest time) have value • Cons Bio : (Leopold, 1886-1948) – can include both value systems – “To keep every cog and wheel is the first precaution of intelligent tinkering" (Leopold 1943). Aldo Leopold (1886-1948) Evolutionary-Ecological Land Ethic • Biological communities: assemblages of interdependent species • Maintaining the health of natural ecosystems and ecological / evolutionary processes • Humans exist within the ecological community; depend on ecosystem services • Synthetic approach: – Both intrinsic value and utilitarian value Why be concerned about biodiversity loss if extinction is a fact of life? Moderate certainty: extinction rates > by 100 – 1000 times Is extinctioncurrent outpacing speciation potential? 10 – 30 % of mammals, birds and amphibians threatened Major drivers of endangerment From Wilcove 1996 What’s missing? Threats to terrestrial species • Terrestrial habitat loss • 39-50% of land surface transformation • Habitat alteration causes biodiversity loss The greatest cause of biodiversity loss – Farming simplifies communities – Grazing modifies the grassland structure and species composition – Clearing forests removes resources organisms need – Hydroelectric dams turn rivers into reservoirs upstream – Urbanization and suburban sprawl reduce natural communities – A few species (i.e., pigeons, rats) benefit from changing habitats Result of habitat loss • Reduction in total area decrease in size, # of populations local extinctionsfewer species • Reduction in habitat diversity – Reduced species diversity – Cascading effects, co-extinctions Habitat alteration has occurred in every biome Particularly in tropical rainforests, savannas, and tropical dry forests The forested areas of Warwickshire, England Habitat fragmentation • Above and beyond habitat loss • Isolation: reduced immigration, recolonization • Edge effects From Primack 2002 Invasion HOMOGENIZATION – The distribution of species on Earth is becoming more homogenous – The rate of invasion is increasing over time Growth in Number of Marine Species Introductions in North America and Europe Introduced cheatgrass, Bromus tectorum, has transformed the Great Basin shrubsteppe ecosystem • Has increased fire frequency from once/80 years to once/4 years! • Occupies over 5 million hectares of Great Basin Pollution causes biodiversity loss • Harms organisms in many ways – Air pollution degrades forest ecosystems – Water pollution adversely affects fish and amphibians – Agricultural runoff harms terrestrial and aquatic species – The effects of oil and chemical spills on wildlife are dramatic and well known • The damage to wildlife and ecosystems caused by pollution can be severe – But it tends to be less than the damage caused by habitat alteration or invasive species Climate change effects on biodiversity • Range shifts Latitudinal range Altitudinal range • Mis-matched interactions • Reassembled (scrambled) communities • Feedbacks (e.g. vegetation and climate) • Species Endangerment Climate change causes biodiversity loss • Emissions of greenhouse gases warms temperatures – Modifies global weather patterns and increases the frequency of extreme weather events – Increases stress on populations and forces organisms to shift their geographic ranges • Most animals and plants will not be able to cope Warming has been the greatest in the Arctic The polar bear is being considered for the endangered species list Climate change endangers polar bears • Sea ice is the key – Bottom up: habitat for micro-algae – Top down: seal hunting ground; corridors to dens • Loss of sea ice endangers polar bear • Loss of top predator: cascading effects on Arctic food web Climate change can induce coral reef bleaching http://www.ogp.noaa.gov/misc/coral/98bleaching/ Bleached and normally pigmented Pocillopora colonies Oceans and Freshwater Aquatic habitats • If anything are more vulnerable to same threats, with enhanced vulnerability to over-exploitation and pollution • Freshwater – USA: Very high endangerment levels in fish & amphibians (25-40%) and crayfish & molluscs (> 60%) compared to terrestrial vertebrates (15-18% Over-exploitation of global ocean fisheries • > 60% of the world’s fisheries are fully to over exploited, or depleted • By-catch increases fish-catch by 30% Botsford 1997 Conserving biodiversity • Genetic level: seed, egg, sperm banks • Population and species level – science of managing small populations – Captive breeding (zoos/botanical gardens) – Reintroductions – Population management in the wild • Protection (hunting, disease, habitat) • Genetic management (translocations) • Habitat restoration Conserving biodiversity: habitat, species, ecosystem level • Protected areas • Managing the matrix – Restoration – Wildlife-friendly agriculture Protected areas for Biodiversity Conservation • Select the areas that represent and maintain biodiversity over time… (Margules and Pressey 2000) REPRESENTATION Including as many different ecosystems and species in the reserve network Representing the full range of variation (genetic, ecological) present within target species A network of reserves that represents species efficiently • But it may not be so good at maintaining biodiversity – why not? Site selection in the Sierra Nevada foothills for conservation prioritization Maintaining biodiversity over time • Population persistence (viability) • Maintaining ecological processes – E.g. migrations • Maintaining evolutionary processes – Potential for adaptation within populations (genetic diversity) – Selecting areas where rapid speciation is occurring • Response to climate change Reserve design features for persistence SIZE Edge to area ratio Shape Environmental gradients Disturbance regime Corridors Matrix habitat CONNECTIVITY Functional units SIZE Larger size • More species (interactions, functions), S-A relationship • More habitats (interactions, functions) • Larger populations – • Protects vulnerable species – Area demanding: large-bodied, high-trophic level, rare – Habitat specialists (if habitat included) – Species requiring multiple habitat types • Shape Reduced edge/area ratio, edge effects • Disturbance regime: maintenance of disturbance-generated patch heterogeneity • Includes whole functional units • Includes whole environmental gradients SIZE & EDGE EFFECTS Edges create core versus edge habitat Example: many songbirds experience high nest predation near edges in woodlots within sub-urban areas From Prim Shape and edge effects Meffe & Carroll 1997 DISTURBANCE REGIME • Disturbance promotes habitat heterogeneity – By resetting successional sequence in parts of the landscape – Creating patchiness in the landscape which is determined by the temporal and spatial scale of the disturbance(s) Spatial and temporal scale of disturbance varies by type SIZE & DISTURBANCE REGIME • Disturbance promotes habitat heterogeneity – mosaic of patches at different successional stages • Habitat heterogeneity: – supports species requiring multiple habitat types – Supports early successional species (e.g. Heath fritillary butterfly = “Woodman’s follower”) • Size of reserve ideally as big as or bigger than scale of likely disturbances SIZE & FUNCTIONAL UNITS Functionally interdependent ecosystems: e.g. “a complex, dynamic patchwork of mangroves, sea grass bed and reefs” (Moberg & Ronnback 2003) Reserve design features for persistence SIZE: Bigger is better! Edge to area ratio Shape Environmental gradients Disturbance regime Corridors Matrix habitat CONNECTIVITY Functional units CONNECTIVITY • Isolation is a key factor causing loss of species from reserves – Preventing gene flow, maintenance of genetic diversity – Reducing recolonization following extinction (rescue effect) – Preventing access between summer/winter grounds for migratory species – Preventing access to multiple habitat types needed for different life stages – Preventing response to global warming Wildlife overpass Transportation Equity Act for the 21st Century provides funding Managing the Matrix Making matrix “friendly” to wildlife --- Reserve zonation: core, buffer, transition Wildlife friendly farming/Restoration CONNECTIVITY: Multi-scale responses PROBLEM of FRAGMENTATION RESPONSE – Preventing gene flow, maintenance of genetic diversity – Reducing recolonization following extinction (rescue effect) •Create corridors between reserves •Manage the matrix around reserves – Preventing access between summer/winter grounds for migratory species Protect migratory routes/stop-overs – Preventing access to multiple habitat types needed for different life stages – Preventing response to global warming Stop-over sites along songbird migration routes • Neotropical birds • Use radar to detect nocturnal bird movement – Timed to get departure events from stopover points (20-40 min after sunset) – Signal characteristics http://www.njaudubon.org/Education/Oases/RadImages.html Breeding wintering CONNECTIVITY: Multi-scale responses PROBLEM of FRAGMENTATION RESPONSE – Preventing gene flow, maintenance of genetic diversity – Reducing recolonization following extinction (rescue effect) •Create corridors between reserves •Manage the matrix around reserves – Preventing access between summer/winter grounds for migratory species Protect migratory routes/stop-overs – Preventing access to multiple habitat types needed for different life stages •Include whole functional units, disturbance regimes, environmental gradients within reserves or reserve networks – Preventing response to global warming •Include elevational or latitudinal gradients within reserves Designing Masoala National Park, Madagascar •Habitat heterogeneity – connectedness between habitats, marine and terrestrial •Species response to climate change: Include elevational gradients within reserve Masoala, Madagascar New Reserve Design Methods • Represent species or habitats efficiently • Minimize edge effects, maximize clustering • Maximize connectivity Leslie et al. 2003 Ecol App. Biodiversity provides free ecosystem services • Provides food, shelter, fuel • Purifies air and water, and detoxifies wastes • Stabilizes climate, moderates floods, droughts, wind, temperature • Generates and renews soil fertility and cycles nutrients • Pollinates plants and controls pests and disease • Maintains genetic resources • Provides cultural and aesthetic benefits • Allows us to adapt to change The annual value of just 17 ecosystem services = $16 - 54 trillion per year Biodiversity helps maintain ecosystem function • Biodiversity increases the stability and resilience of communities and ecosystems – Decreased biodiversity reduces a natural system’s ability to function and provide services to our society • The loss of a species affects ecosystems differently – If the species can be functionally replaced by others, it may make little difference – Extinction of a keystone species may cause other species to decline or disappear • “To keep every cog and wheel is the first precaution of intelligent tinkering” (Aldo Leopold) Biodiversity enhances food security • Genetic diversity within crops is enormously valuable – Turkey’s wheat crops received $50 billion worth of disease resistance from wild wheat • Wild strains provide disease resistance and have the ability to grow back year after year without being replanted • New potential food crops are waiting to be used – Serendipity berry produces a sweetener 3,000 times sweeter than sugar Organisms provide drugs and medicines • Each year pharmaceutical products owing their origin to wild species generate up to $150 billion in sales – The rosy periwinkle produces compounds that treat Hodgkin's disease and leukemia Biodiversity generates economic benefits • People like to experience protected natural areas, creating economic opportunities for residents, particularly in developing countries – Costa Rica: rainforests – Australia: Great Barrier Reef – Belize: reefs, caves, and rainforests • A powerful incentive to preserve natural areas and reduce impacts on the landscape and on native species • But, too many visitors to natural areas can degrade the outdoor experience and disturb wildlife Do we have ethical obligations to other species? • Humans are part of nature and need resources to survive • But, we also have conscious reasoning ability and can control our actions – Our ethics have developed from our intelligence and our ability to make choices • Many people feel that other organisms have intrinsic value and an inherent right to exist Conservation scientists work at multiple levels • Conservation biologists integrate evolution and extinction with ecology and environmental systems – Design, test, and implement ways to mitigate human impacts • Conservation geneticists = study genetic attributes of organisms to infer the status of their population • Minimum viable population = how small a population can become before it runs into problems • Metapopulations = a network of subpopulations – Small populations are most vulnerable to extinction and need special attention Island biogeography • Equilibrium theory of island biogeography = explains how species come to be distributed among oceanic islands – Also applies to “habitat islands” – patches of one habitat type isolated within a “sea” of others – Explains how the number of species on an island results from an equilibrium between immigration and extirpation – Predicts an island’s species richness based on the island’s size and distance from the mainland Species richness results from island size and distance • Fewer species colonize an island far from the mainland • Large islands have higher immigration rates • Large islands have lower extinction rates The species-area curve • Large islands contain more species than small islands – They are easier to find and have lower extinction rates – They possess more habitats Small “islands” of forest rapidly lose species • Forests are fragmented by roads and logging • Small forest fragments lose diversity fastest – Starting with large species • Fragmentation is one of the prime threats to biodiversity Should conservation focus on endangered species? • Endangered Species Act (1973) (ESA) = forbids the government and private citizens from taking actions that destroy endangered species or their habitats – To prevent extinction – Stabilize declining populations – Enable populations to recover • As of 2007, the U.S. had 1,312 species listed as endangered or threatened Despite opposition, the ESA has had successes • Peregrine falcons, brown pelicans, bald eagles, and others have recovered and are no longer listed • Intensive management has stabilized other species – The red-cockaded woodpecker – 40% of declining populations are now stable • These successes occur despite underfunding of the U.S. Fish and Wildlife Service and the National Marine Fisheries Service – In recent years, political forces have attempted to weaken the ESA The ESA is controversial • Many Americans support protection of endangered species • Opponents feel that the ESA values endangered organisms more than the livelihood of people – Private land use will be restricted if an endangered species is present – “Shoot, shovel, and shut up” = landowners conceal the presence of endangered species on their land • But, the ESA has stopped few development projects – Habitat conservation plans and safe harbor agreements = landowners can harm species if they improve habitat for the species in other places Other countries have their own version of the ESA • Species at Risk Act (2002) = Canada’s endangered species law – Stresses cooperation between landowners and provincial governments – Criticized as being too weak • Other nations’ laws are not enforced – The Wildlife Conservation Society has to help pay for Russians to enforce their own anti-poaching laws Protecting biodiversity • Captive breeding – individuals are bred and raised with the intent of reintroducing them into the wild – Zoos and botanical gardens • Some reintroductions are controversial – Ranchers opposed the reintroduction of wolves to Yellowstone National Park – Some habitat is so fragmented, a species cannot survive Protecting biodiversity • Cloning – a technique to create more individuals and save species from extinction – Most biologists agree that these efforts are not adequate to recreate the lost biodiversity • Ample habitat and protection in the wild are needed to save species Umbrella species • Conservation biologists use particular species as tools to conserve communities and ecosystems – Protecting the habitat of these umbrella species helps protect less-charismatic animals that would not have generated public interest • Flagship species – large and charismatic species used as spearheads for biodiversity conservation – The World Wildlife Fund’s panda bear • Some organizations are moving beyond the single species approach to focus on whole landscapes International conservation efforts • UN Convention on International Trade in Endangered Species of Wild Fauna and Flora (1973) (CITES) – protects endangered species by banning international transport of their body parts • Convention on Biological Diversity (1992) – – Seeks to conserve biodiversity – Use biodiversity in a sustainable manner – Ensure the fair distribution of biodiversity’s benefits – By 2007, 188 nations had signed on – Iraq, Somalia, the Vatican, and the U.S. did not join Community- based conservation • Protecting habitats makes good sense, but this affects people living in and near these areas • Community-based conservation = conservation biologists actively engage local people in protecting land and wildlife – Protecting land deprives people access to resources – But, it can guarantee that these resources will not be used up or sold to foreign corporations and can instead be sustainably managed • Many projects have succeeded – But, others have not, due mainly to funding Innovative economic strategies • Debt-for-nature swap = a conservation organization pays off a portion of a developing country’s international debt – In exchange for a promise by the country to set aside reserves – Fund environmental education, and – Better manage protected areas • Conservation concession = conservation organizations pay nations to conserve, and not sell, resources Conclusions • Biodiversity has great value, both intrinsically, and also because human life depends on it • But, it is under threat, from habitat loss and degradation, invasive species, climate change, pollution and over-exploitation • Conservation biologists have many tools to protect biological diversity, from genetic to ecosystem levels. Conclusions • Protected areas are an important tool for biodiversity conservation. • The design of protected areas and reserve networks should foster representation of biodiversity and its persistence. – Reserves need to be sited efficiently to represent biodiversity. – Size, shape and connectivity of reserves and relationship with the surrounding landscape matrix are essential considerations for biodiversity persistence.
