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Chapter 9- Conservation of Species and Habitats.docx

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University of Toronto Mississauga
Monika Havelka

Chapter 9- Conservation of Species and Habitats Value of Biodiversity Biodiversity Provides goods and services  Provides food, shelter, fuel  Purifies air and water, detoxifies wastes  Generates and renews soil fertility  Pollinates plants, controls pests and disease  Maintains genetic resources  Provides culture and aesthetic benefits  Allows us to adapt to change Organisms provide drugs and medicines  Plants: in response to herbivory, they produce: cyanide, caffeine, cocaine, mescaline, nicotine, atropine, strychnine, morphine, quinine, codeine, digitalis, and many more Eco-Tourism  Incentive to preserve natural areas and reduce impacts on the landscape and on native species  Particularly beneficial in developing countries  Thus, preserving biodiversity is economically important Deep ecology- concepts that nature has intrinsic rights and value  Do other organisms have intrinsic value?  Do other organisms have rights, including an inherent right to exist?  Do we have ethical obligations toward other species? Biodiversity helps maintain ecosystem functions  Biodiversity increases the stability and resilience of communities and ecosystems  Decreased biodiversity reduces natural system’s ability to function and provide services Measuring Biodiversity Species Diversity  Abundance= number of individuals  Richness= number of different species  Evenness= distribution of abundance over species  These three measures can be used to describe species richness: o Alpha- Diversity= # of species in local area of homogeneous habitat o Gama Diversity= # of species in large geographic area that comprises many habitats o Beta Diversity= turnover in species from one local area to another = gama/alpha  If the same species are found in different habitats over a wide area, then: Gama= Alpha and Beta=1  If different species are found in different habitats over wide area, then beta > 1 (high beta diversity)  If species are mostly generalist, beta diversity is low  If species are mostly specialists, beta diversity is high  Leopard frog: found in lakes, rivers, ponds, streams, wetlands  Tailed frog: Only in cold, clear mountain streams, sensitive to siltation warming Amazon Basin  300 tree spp per hectare  Tree species composition changes little over > 1,400 km  beta is low Isthmus of Panama  Smaller than South Carolina  Completely different tree assemblages 50 km apart  beta is high Implications for conservation design  SLLOSS debate: Single large or several small  Now known as Biological dynamics of forest fragments project, Manaus Brazil  Previously known as Minimum critical size of ecosystems project  “Nestedness” of species is a critical concept  If there is a small area vs. a large area, are small areas subsets of large areas or do they represent unique areas Factors that Affect Biodiversity Factors that drive species richness (number of different species)  Spatial factors: area size, proximity, fragmentation & isolation o Area size and proximity o Smaller the area, the fewer the species o Why is # of species a function of area?  Habitat heterogeneity: larger geographic areas will have a greater variety of habitat types and more niches  Population Buffers: Large areas have large populations, which are less likely to die out through stochastic (random) processes  Number of species in an area= equilibrium between the number arriving and the number dying out o Equilibrium theory of Island Biogeography  Trapped large animals and killed insects so islands in experiment had no insect life and kept coming back and sampling how many species of insects ended up on each island  The rate at which species go extinct on an island is a function of the number of species present (due to species interactions; niche space)  Most extinction happens by species interaction  The extinction rate will be higher on small islands than large islands (due to random loss; habitat heterogeneity)  The rate at which species immigrate (establish there) to an island is a function of the number of species present (due to species interactions; niche space)  The immigration rate will be higher on islands near to the mainland than islands far from
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