Bài giảng habitat loss and degradation

Threats to Biodiversity Habitat Loss and Degradation Significant and largely irreversible changes to biodiversity in the world – The distribution of species on Earth is becoming more homogenous – The population size or range (or both) of the majority of species across a range of taxonomic groups is declining – Humans have increased the species extinction rate by as much as 1,000 times over background rates typical over the planet’s history (medium certainty) – 10–30% of mammal, bird, and amphibian species are currently threatened with extinction (medium to high certainty) Unprecedented change: Ecosystems – – 5-10% of the area of five biomes was converted between 1950 and 1990 More than two thirds of the area of two biomes and more than half of the area of four others had been converted by 1990 Millenium Ecosystem Assessment Assessment Synthesis Report http://www.maweb.org/ Unprecedented change: Biogeochemical Cycles • Since 1960: – Flows of biologically available nitrogen in terrestrial ecosystems doubled – Flows of phosphorus tripled • > 50% of all the synthetic nitrogen fertilizer ever used has been used since 1985 • 60% of the increase in the atmospheric concentration of CO2 since 1750 has taken place since 1959 Human-produced Reactive Nitrogen Humans produce as much biologically available N as all natural pathways and this may grow a further 65% by 2050 Human Population Growth Source: Data from U.S Census Bureau World Population Clock Human Footprint Source: Sanderson et al., 2002 • Biodiversity is in decline due to a diversity of threats (direct threats: overexploitation, habitat loss, pollution, etc and indirect threats: poverty, population growth etc.) Threats Biodiversity Direct • Habitat loss and degradation • Overexploitation • Invasive species • Pollution • Global climate change Underlying (indirect) • Overpopulation • Over-consumption • Reduced or negative incentives to conserve • Lack of enforcement Road Construction - Roads damage habitat - Roads cause habitat fragmentation - Roads increase disturbance - Roads limit movement of wildlife - And more… Source: NASA Effects of road on exotic/native plant species Source: Gelbard and Belnap, 2003 Survival rate before and after dam construction Source: Raymond, 1979 Deforestation ■ Forests are habitat for a majority of the earth’s known species ■ Forests are being lost faster than they are growing Source: nimbuseco.com ■ Forests cover less than 6% of the earth’s total surface area Effects and Types of Fragmentation • Loss of Ecosystems and Habitats • Decreased Patch Size • Increased Edge Effects • Increased Patch Isolation • Changes in Species Diversity, Composition and Interactions Area: 16 sq km Edge: 32 km Source: Murphy©AMNH-CBC Area: 16 sq km Edge: 16 km Dispersal and fragmentation Source: Gibbs Habitat quality: Interior vs Edge Edge zone: - Windier - Drier - Warmer - Higher competition between: Native and exotic species - More disturbance Edge Effects • Physical – Microclimate changes in light, temperature, & wind – Humidity  100m • Biological – Exotic Plants and Insects – Invasive Plants, Insects and animals – Bird Density  100m • Synergistic – Fire – Hunting pressure by humans and other predators Frey © AMNHCBC Nature of Fragmentation Natural SOURCE: DEPARTMENT OF THE INTERIOR, A ADAMS Complex patch Less distinct edge Human Caused SOURCE: FREY©CBC-AMNH Distinct Edge Simplified Patch Loss and Degradation of Natural Habitat - It is estimated that forests (including mangroves) cover about 17.4 to 27.5 percent of the country, but only a small subset of this area can be considered in healthy condition - Primary forest continues to decrease drastically and presently covers less than 10% of the country’s land (MOSTE, 1998; Poffenberger and Nguyen, 1998) Kevin Frey/CBC-AMNH Loss and Degradation of Natural Habitat Source: World Bank, 2005 Wetlands • Fresh and Marine – Drained – Filled – Developed All photos Source: National Oceanic & Atmostpheric Administration Commerce Department Changes in mangrove forest area Source: World Bank, 2005 Causes • Agriculture • Resource Extraction • Human Settlement • Industrial Development Source: Frey©AMNH-CBC Causes of Deforestation - Uncontrolled logging - Agricultural expansion Don Pirot - Road construction Ned Horning Causes of Deforestation - Fire wood collection - Ultimately, pressures from high population growth Craig Lieb Forest Islands [...]... Loss and Degradation of Natural Habitat - It is estimated that forests (including mangroves) cover about 17.4 to 27.5 percent of the country, but only a small subset of this area can be considered in healthy condition - Primary forest continues to decrease drastically and presently covers less than 10% of the country’s land (MOSTE, 1998; Poffenberger and Nguyen, 1998) Kevin Frey/CBC-AMNH Loss and Degradation. .. of the earth’s total surface area Effects and Types of Fragmentation • Loss of Ecosystems and Habitats • Decreased Patch Size • Increased Edge Effects • Increased Patch Isolation • Changes in Species Diversity, Composition and Interactions Area: 16 sq km Edge: 32 km Source: Murphy©AMNH-CBC Area: 16 sq km Edge: 16 km Dispersal and fragmentation Source: Gibbs Habitat quality: Interior vs Edge Edge zone:... Changing turbidity - Filtering out of woody debris which provides habitat and sustain a food change -Trapping silt in reservoirs and reducing downstream productivity - Changing temperature and oxygen conditions Source: bashny.net - And more … Survival rate before and after dam construction Source: Raymond, 1979 Deforestation ■ Forests are habitat for a majority of the earth’s known species ■ Forests are... Windier - Drier - Warmer - Higher competition between: Native and exotic species - More disturbance Edge Effects • Physical – Microclimate changes in light, temperature, & wind – Humidity  100m • Biological – Exotic Plants and Insects – Invasive Plants, Insects and animals – Bird Density  100m • Synergistic – Fire – Hunting pressure by humans and other predators Frey © AMNHCBC Nature of Fragmentation... decrease drastically and presently covers less than 10% of the country’s land (MOSTE, 1998; Poffenberger and Nguyen, 1998) Kevin Frey/CBC-AMNH Loss and Degradation of Natural Habitat Source: World Bank, 2005 Wetlands • Fresh and Marine – Drained – Filled – Developed All photos Source: National Oceanic & Atmostpheric Administration Commerce Department Changes in mangrove forest area Source: World Bank,... Uncontrolled logging - Agricultural expansion Don Pirot - Road construction Ned Horning Causes of Deforestation - Fire wood collection - Ultimately, pressures from high population growth Craig Lieb Forest Islands