Conservation Biology lecture 28 PDF

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Conservation Biology I.

Biodiversity Number and types of species and their abundance in a given location or on the planet 1.8 million species described and named 10-100 million more species still out there! A. Levels of diversity 1. Genetic Variation within and between populations 2. Species Variety of species in ecosystem/biosphere 3. Ecosystem Variety of ecosystems in biosphere

B. Benefits of biodiversity 1. Biophilia Sense of connection to nature and all life Philosophical and moral justifications 2. Products for human use Ex: ~25% of pharmacy prescriptions contain substances derived from plants (Fig.47.8 Madagascar periwinkle is source of vincristine, a drug used in the treatment of lymphomas 3. Genetic resources Ex: genes from wild plants could improve related crop species 4. Ecosystem services Processes through which natural ecosystems help sustain human life Air and water purification Waste decomposition Reduce impact of extreme weather and flooding Crop pollination No monetary value → ecosystem services undervalued C. Threats to biodiversity 1. Habitat loss (via) Agriculture Urban development Mining Forestry Pollution 2. Introduced species = exotic species Accidental and intentional movement by humans of species from native locations to new geographic regions Native habitat → Limited by predators, parasites, pathogens In new habitat → No constraints so may spread rapidly Global problem → ~40% of extinctions since 1750

(Fig.47.12 The brown tree snake has caused numerous extinctions on the island of Guam since its accidental introduction in 1950) 3. Overharvesting Harvesting of wild organisms at rates exceeding ability of population to rebound Species most at risk: Restricted habitats Low reproductive rate (K-selected) Ex: elephants, rhinos, whales 4. Global change Alterations in climate, atmospheric chemistry, and ecological systems → Reduce capacity of Earth to sustain life (Fig.47.15 Grizzly bear populations spreading) Grizzly bears have been spotted farther north than their historic range. Grizzly bear habitat now overlaps polar bear habitat. Considered separate species as historically they lived in different habitats and never met. The two are capable of mating and producing viable offspring. In 2006, a hunter shot a wild grizzly-polar bear hybrid known as a grolar bear. D. Extinction Natural phenomenon (Fig.47.5 Mass extinctions) Current high rate of extinction → Species-level - public awareness Human activities throughout biosphere Altering trophic structures, E flow, and chemical cycling → Causing more extinctions than asteroid that triggered mass extinction 65.5 mya Threatened Considered likely to become endangered in near future (ex: beluga) Endangered In danger of extinction throughout all or significant portion of range (ex: Florida panther) Local extinction Species lost in one particular area Global extinction Species lost from all ecosystems in which it lived Conservation biology Integrates molecular biology, genetics, physiology, ecology, and evolutionary biology → conserve biodiversity II. Population conservation A. Small population approach 1. Extinction vortex 2. Minimum viable population (MVP) Minimum size for population to sustain itself Estimated using computer models that consider many factors 3. Effective population size

What actually matters is which members will breed (not total population number) Breeding potential of population Ne = (4NfNm)/(Nf + Nm) Ex: idealized population of 1,000 individuals Sex ratio is 500 females to 500 males Every individual breeds Ne = (4x500x500)/(500 + 500) = 1000 B. Declining population approach 1. Focuses on populations in downward trend even if not yet at MVP 2. Emphasizes environmental factors that cause population decline 3. Ex: red-cockaded woodpecker a. Normal habitat is pine forests in southeastern US b. Forest needs low undergrowth of plants around pine trees → Fires keep undergrowth low c. Habitat destruction and fragmentation Result of logging and agriculture → Woodpecker population decline d. Recognition of key habitat factors Protecting pine forests Controlled fires to reduce forest undergrowth Habitat restoration → Viable populations C. Conflicting demands 1. Society vs. biodiversity conservation Ex: restocking of wolves in Yellowstone Wolf population vs human and livestock safety 2. Ecological role of a species Cant save every endangered species → Which is most important? Determine which species is most important for conserving biodiversity as a whole → What are keystone species? (greatest impact on ecosystem) (Fig.47.17 Gibbon wolf pack in Yellowstone national park represents a keystone species) Wolves reintroduced into Yellowstone in 1995 → To avoid predation, elk no longer grazed exposed stream and riverbeds → Willow and cottonwood seedlings could grow; decreased erosion and provided shade Improved fish habitat Beavers also benefitted from the habitat change Goals of conservation Historic → save individual species Current → broader scope; sustain biodiversity of entire communities, ecosystems, and landscapes III. Landscape conservation Several different ecosystems linked by exchanges of E, matter, and organisms A. Edges and fragmentation

1. Edge Boundary between ecosystems Physical conditions which differ from those on either side Ex: between lake and surrounding forest 2. Fragmentation Habitat broken into smaller pieces → Increases amount of edges 3. Some organisms thrive in edges because use resources from both areas 4. As habitats become more fragmented and edges increase → biodiversity decreases because only edge species will thrive Fragmentation Populations in habitat fragments have higher probability of local extinction 5. Movement corridor Narrow strip that connects habitat fragments Promote dispersal and reduces inbreeding Can promote spread of parasites and disease B. Establishing protected areas → Attempt to slow biodiversity loss 1. Biodiversity hot spots a. Relatively small area with numerous endemic species (found nowhere else) and many threatened and endangered species b. Can be difficult to identify Hot spot for one group of organisms may not be hot spot for another (Fig.47.4 34 biodiversity hotspots) 2.3% of Earth’s surface 42% of terrestrial vertebrate species 50% of plant species 2. Nature preserves a. Protected “islands” of biodiversity in a sea of habitat altered by human activity b. Management policy considerations How are natural disturbances managed? Ex: some ecosystems are fire-dependent Many small reserves vs fewer large reserves? Ex: large far-ranging species may need larger areas than smaller organisms 3. Urban ecology Species preservations in cities Cities expanding in size → Incorporating protected areas previously outside of city Balancing species preservation and other ecological concerns with needs of people IV. Effects of human activity on Earth A. Nutrient enrichment 1. Farming

a. Crops grown → Use nutrients in soil at that location Instead of decomposing and recycling nutrients back into soil Plants harvested and exported → Nutrients leave farm soil Natural store of nutrients in soil eventually exhausted b. Use of fertilizers N is main nutrient lost through agriculture Fertilizers increase amount of fixed N in soil 2. Critical load Amount of added nutrients that can be absorbed by plants without damaging ecosystem integrity When critical load exceeded → Excess can be hazardous Nitrogenous minerals that exceed critical load → Leach into groundwater Water unsafe to drink Run off into aquatic environments → Eutrophication → Kills fish B. Toxins 1. Humans release many toxins into environment Many are synthetic compounds → Unknown in nature Little regard for ecological consequences Organisms acquire toxic substances from environment along with nutrients and water 2. Biological magnification Accumulation of toxins become more concentrated in successive trophic levels a. Ex: DDT Pesticide which contains chlorinated hydrocarbons Endocrine disrupter in many animals including humans Rachel Carson’s book Silent Spring → DDT banned in US Still used in other parts of world to control mosquitoes b. Ex: Pharmaceuticals Drugs excreted in waste If not broken down in sewage treatment plants → Enter lakes and rivers Spreading in low concentrations across world’s freshwater ecosystems Ex: estrogens Fish are very sensitive Very low concentrations (a few parts per trillion) Can alter sex differentiation and shift sex ratios toward females C. Greenhouse gases 1. Greenhouse effect Much of solar radiation that strikes Earth reflected back into space Gases in atmosphere

Ex: CO2, methane, and water vapor Absorb much of IR radiation and re reflect it back to Earth → Planet retains heat and can sustain life Problem Increased levels of greenhouse gases now trapping too much heat → Global temperatures rising 2. Carbon dioxide Levels increasing as a result of burning fossil fuels and deforestation 3. Climate change solutions More efficient use of energy Replacing fossil fuels with renewable solar and wind power Stabilizing CO2 emissions Reduce deforestation → conserve biodiversity We are most likely to protect what we understand → Learning about the processes and diversity of life is critical...