Habitat loss and degradation PVA: Essay 12.2 (and adjacent text) - PDF document

Book reading that covers lectures up to the test Habitat loss and degradation PVA: Essay 12.2 (and adjacent text) Loss: Irreversible damage of a habitat Species invasion: p 293 - 331 (Case study 9.4 is informative Degradation: permanent or temporal degradation (reduction on biological control), no other boxes or essays. Some parts of its function) of a habitat in this chapter were not discussed in class. Transformation from one type into another one Overexploitation: p 257-258, p 260-262 p 265 - 274 !! (no Box or Essays) Habitat degradation: p 174-188, Essay 6.1 Habitat fragmentation: p 213-234, Essay 7.1, Box 7.1 Loss of rain forest Source of 1620, 1850, and 1920 maps: William B. Greeley, The Relation of Geography to Timber Supply, Economic Geography, 1925, vol. 1, p. 1-11. Source of TODAY map: compiled by George Draffan from roadless area map in The Big Outside: A Descriptive Inventory of the Big Wilderness Areas of the United States, by Dave Foreman and Howie Wolke (Harmony Books, 1992)hi. Loss of wetlands

Longleaf pine forests degradation Fringed prairie orchid loss transformation Fragmentation Process of fragmentation Effects on habitat Native habitat Transformed habitat Gap formation Fragmentation Time Western Warwickshire, Madagascar, England 500-1990 400 - 1960

Willamette US Pacific National Northwest, Forest, 1940-1981 Oregon, 1979 Major changes in fragmented Habitat “shredding” habitats natural Size: decreases Isolation: increases Edge/interior: increases “shreds” Native habitat Transformed habitat Shredding Patchy Habitat fragmentation isolated patches (island biogeography) fragments have small area and (typically) a center and an edge Habitat shredding connected to “good” habitats (theory?) consists mostly of edge

Fragmentation and Heterogeneity Fragmentation and Heterogeneity Fragmentation and Heterogeneity Fragmentation and Heterogeneity Quantifying fragmentation Shannon-Wiener variant H ∗ = − � k p k ln p k ln s Shannon-Wiener index p k = frequency of map class k Shape complexity s = total number of map classes Proximity index spatial statistics Range of H* is scaled between 0 and 1 0 → low diversity and uneven habitat classes 1 → high diversity and even habitat classes

Comparison of such indices! Complexity of habitat patches log A ∼ d log P Shannon - Wiener ignores shape (interior versus edge) A = area of a patch Complexity measures only within patch class, but takes edge P = perimeter of a patch versus interior into account d = fractal dimension Simple indices often do not tell the (whole) truth d is found by regression and then scaled between 1 and 2. A value of two means more edge per patch and a value of 1 is equivalent with circular patches. Fragmentation Roads increase invasives Effects on habitat Effects on species Wilderness designation Importance of roads Fragmentation Spread if invasive species Settlement/Development Wilderness designation • Is the area 5,000 acres in size or larger? Or a roadless island? • Does the area generally appear to be natural and is human presence relatively unnoticeable? • Does the area offer the opportunity for primitive and unconfined recreational activities like camping, hiking, and skiing? • Does it provide opportunities for solitude? • Does the area contain features of ecological , geological , scientific , educational , scenic , or historical significance? http://www.wilderness.net/index.cfm?fuse=NWPS&sec=designation total = 106,402,582acres

Effects of fragmentation on species: Fragmentation small patches and isolation Genetic drift Effects on habitat Inbreeding Effects on species Heterozygosity Effects of smaller patches Population size Effects of isolation Demographic stochasticity Migration, gene flow Colonization / Extinction Diversity Area effect, distance effects (Island biogeography theory) Area effect Distance effect � Demographic stochasticity � Patch isolation � Patch size � Gene flow Extinction � Population size Migration � local adaptation, � FST, � Genetic drift, � Extinction risk � Colonization � Patch � inbreeding, � inbreeding, � Colonization occupancy � heterozygosity � heterozygosity � Metapopulation � Diversity � Diversity Relaxation: adjusting to a lower level of diversity Relaxation = reduction in diversity of a patch after fragmentation after isolation from old “equilibrium” number of species to new equilibrium number. Habitats that are fragmented will adjust to a lower level of diversity Wolves Islands that were once connected to the mainland will adjust Coyotes Elk to a lower level of diversity Coyotes Elk Islands that never were connected to a mainland will build up diversity Pronghorn Plants Pronghorn Plants

Fragmentation Fragmentation Effects on habitat Effects on habitat Effects on species Effects on species Effects of smaller patches Effects of smaller patches Diversity � , Extinction � Diversity � , Extinction � Effects of isolation Effects of isolation Edge effects Edge effects Edge effects = edges of habitat are not the same as “interior” of habitat (biotic and abiotic differences) Field Forest Forest “edge” Forest Field Field Edge effects = edges of habitat are not The smaller the patch, the more edge the same as “interior” of habitat (biotic relative to interior and abiotic differences) Edges have: 1 Ha � � � 10 Ha �� � 100 Ha more light higher temperature 100% less moisture edge 48% interior different species 53% edge higher extinction rates If edge width is 50 m 81% interior 19% edge

Fragmentation None of 16 species breed Effects on habitat Effects on species Effects of smaller patches Diversity � , Extinction � Effects of isolation Edge effects Species composition changes, Extinction � 6 of 16 species breed Biological Dynamics of Forest Fragments (BDFF) Secondary Extinctions Brazilian Amazon Extinctions resulting from other extinctions Initiated in 1979 by WWF and INPA

Summary of BDFF edge effects: Fragment sizes: 1, 10, 100, 1000 Ha; Plus continuous forest Abiotic variables Biotic variables Decrease in species richness of birds, some � insects, primates, bees, and termites Increase in species richness of small � mammals, amphibians, and butterflies Changes in composition of communities of � butterflies and small mammals Plots are square with side: 100m, 316m, 1000m, 3162m Fragmentation Landscape context Native habitat Transformed habitat Effects on habitat Effects on species Forest fragmentation project in Brazil Landscape context Effect of urbanization Study of e � ects of urban land on reserves: Shortgrass steppe 66 study plots in four grassland types • Shortgrass steppe • Mixed grass prairie • Tallgrass prairie • Hayfields

Mixed grass prairie Tallgrass prairie Hayfields Hispid pocket mouse Grasshopper sparrow 2 Abundance index 1.5 1 0.5 0 0 10 20 30 Measure of Landscape suburbanized (%) landscape Urban index context Bock et al. 2002, Conservation Biology Haire et al. 2000, Landscape and Urban Planning

Fragmentation “What do we know for sure?” Rate of extinction Harrison and Bruna 1999 versus park area (Newmark 1995) Species in fragmented habitats are vulnerable to extinction Medium-large mammals Fragmentation of landscape as a cause for genetic subdivision of bank vole populations. Gabriele Gerlach and Kerstin Musolf Conservation Biology 14 (2000) 1 – 10 We studied the barrier effects of various roadways on genetic subdivision of bank vole ( Clethrionomys glareolus ) populations. Allele frequencies, genetic variability, and genetic distances of natural populations were calculated based on polymorphism of 7 microsatellite markers. We compared bank vole populations in control areas without such barriers with animals from both sides of a country road, a railway, and a highway, all roadways older than 25 years. Using F- and R-statistics, we demonstrated significant population subdivision in bank vole populations separated by the highway, but not in populations on either side of the other roadways or in the control area. Correlations between geographic and genetic distances were revealed by an extended method based on a Mantel analysis. This allowed us to measure genetic barrier effects and express them as additional geographic distances. For instance, statistically significant differences in allele frequencies in all 7 loci examined existed among populations in southern Germany and Switzerland, which are separated by the Rhine River and Lake Constance. The real geographic distance between bank vole populations in Konstanz and those in Lengwil, Switzerland, is 6 km. According to this analysis the genetic barrier effect of the Rhine could be defined as an additional distance of 7.7 km.