Transcript Chapter 9
ENVIRONMENTAL SCIENCE 13e CHAPTER 9: Sustaining Biodiversity: The Ecosystem Approach Wangari Maathai and the Green Belt Movement • • • • Began in Kenya in 1977 Organizes poor women in rural Kenya 50,000 members protect forests Planted 20 million trees – Fruits – Building materials – Firewood • Similar programs in 30 African countries • 2004: Nobel Peace Prize 9-1 What Are Major Threats to Forest Ecosystems? • Concept 9-1 Ecologically valuable forest ecosystems are being cut and burned at unsustainable rates in many parts of the world. Types of Forests • Forests cover 30% of earth’s land surface • Old-growth forests • Second-growth forests • Tree plantation Science Focus: Putting a Price Tag on Nature’s Ecological Services • Estimated value of earth’s ecological services – $33.2 trillion per year – $4.7 trillion per year for forests • Need to start factoring values into land use • Ecological services can be a sustainable source of ecological income Harvest Methods • Step one: build roads – Erosion – Invasive species – Open up for human invasion • Step two: logging operations – Selective cutting – Clear cutting – Strip cutting Forests and Fires • Surface fires – Burn undergrowth only – Cool fire – Ecological benefits • Crown fires – Burn the entire tree – Hot fire – Occur in forests with lack of surface fires Loss of Original Forests • Deforestation • 46% in 8,000 years, most since 1950 • Most in tropical areas, developing countries • Estimated loss of 40% intact forests within next 20 years Good News on Forests • 2000–2007 net total forested area stabilized or increased • Most of the increase due to tree plantations • Net loss of terrestrial biodiversity Return of Forests in the United States (1) • U.S. forests – Cover ~30% of land – Contain ~80% of wildlife species – Supply ~67% of nation’s surface water • Forest cover greater now than in 1920 • Secondary succession Return of Forests in the United States (2) • Second- and third-growth forests fairly diverse • More wood grown than cut • 40% of forests in National Forest System • Some forests transformed into tree plantations Tropical Forests • Cover 6% of earth’s land area • Habitat for 50% of terrestrial plants and animals – Vulnerable to extinction – specialized niches • Rapid loss of 50,000–170,000 km2 per year • Some second-growth forests Causes of Tropical Forest Deforestation and Degradation • Population growth and poverty • Economic reasons – Logging – Ranching – Farming • Government subsidies • Fires raise temperatures and reduce rainfall 9-2 How Should We Manage and Sustain Forests? • Concept 9-2 We can sustain forests by emphasizing the economic value of their ecological services, removing government subsidies that hasten their destruction, protecting oldgrowth forests, harvesting trees no faster than they are replenished, and planting trees. Management of Forest Fires (1) • Fire suppression in all types of forests • Increased amounts of underbrush • Increased probability of crown fires Management of Forest Fires (2) • • • • • Prescribed fires Allow some fires to burn Thin vegetation from forests Thin around vulnerable homes Decrease flammability of homes Science Focus: Certifying Sustainably Grown Timber • Forest Steward Council certification of forest operations – Environmentally sound practices – Sustainable yield harvest – Minimal erosion from operations – Retention of dead wood for wildlife habitat Trees and Paper • Many trees are cut for paper production • Alternatives – Pulp from rice straw and agricultural residues (China) – Kenaf (U.S.) – Hemp 9-3 How Should We Manage and Sustain Grasslands? • Concept 9-3 We can sustain the productivity of rangeland by controlling the number and distribution of grazing livestock and by restoring degraded grasslands. Grasslands • Provide important ecological services • Second most used and altered ecosystem by humans • 42% grazed by cattle, sheep, and goats – rangeland (open) and pasture (fenced) • Overgrazing 9-4 How Should We Manage and Sustain Parks and Nature Reserves? • Concept 9-4 We need to put more resources into sustaining existing parks and nature reserves and into protecting much more of the earth’s remaining undisturbed land area. National Parks • >1,100 national parks in 120 countries • Only 1% of parks in developing countries are protected – Local people invade parks to survive – Logging – Mining – Poaching Problems Protecting National Parks • • • • Illegal logging Illegal mining Wildlife poaching Most parks too small to protect large animals • Invasion of nonnative species Stresses on U.S. National Parks • • • • • 58 major national parks Biggest problem is popularity Damage from nonnative species Threatened islands of biodiversity Need $6 billion for overdue repairs Nature Reserves Occupy a Fraction of Earth • 12% of earth’s land protected • Only 5% fully protected – 95% reserved for human use • Need for conservation – Minimum 20% of land in biodiversity reserves – Protection for all biomes Solutions for Protection • “Ecological insurance policy” • Buffer zones around protected areas • Locals to manage reserves and buffer zones • United Nations: 531 biosphere reserves in 105 countries Science Focus: Reintroducing the Gray Wolf to Yellowstone National Park • Reduced to a few hundred in lower 48 by 1973 • Keystone species • Restoration proposal angered ranchers, hunters, loggers • 1995 - reintroduced in Yellowstone, 124 by 2008 • Positive ripple effect after reintroduction Case Study: Costa Rica • Superpower of biodiversity • Conserved 25% of its land, 8 megareserves • Government eliminated deforestation subsidies • Paid landowners to maintain and restore tree coverage • Boosts ecotourism Protecting Wilderness Protects Biodiversity • Wilderness • Preserves biodiversity • Centers for evolution Case Study: Controversy over Wilderness Protection in the U.S. • 1964 Wilderness Act • Ten-fold increase from 1970 to 2008 • 4.6% of U.S. land protected, 75% of that in Alaska 9-5 How Can We Help to Sustain Terrestrial Biodiversity? • Concept 9-5 We can help to sustain terrestrial biodiversity by identifying and protecting severely threatened areas (biodiversity hotspots), rehabilitating damaged ecosystems (using restoration ecology), and sharing with other species much of the land we dominate (using reconciliation ecology). Three Principles to Protect Ecosystems 1. Map and inventory the world’s terrestrial and aquatic ecosystems 2. Locate and protect the most endangered ecosystems, with a focus on biodiversity 3. Seek to restore as many degraded ecosystems as possible Protecting Global Biodiversity Hotspots • 17 megadiversity countries, mostly in tropics and subtropics – Two-thirds of biodiversity • Developing countries economically poor and biodiversity rich • Protect biodiversity hotspots Ecological Restoration • • • • Restoration Rehabilitation Replacement Creating artificial ecosystems Science-based Principles for Restoration • • • • Identify cause of degradation Stop abuse by reducing factors Reintroduce species if necessary Protect area from further degradation Case Study: Ecological Restoration of Tropical Dry Forest in Costa Rica • One of world’s largest ecological restoration projects • Restore a degraded tropical dry forest and reconnect it to adjacent forests • Involve 40,000 people in the surrounding area – biocultural restoration • Ecotourism Restoration Ecology • Creating new habitats to conserve species diversity in areas where people live, work, play • People learn to protect local species and ecosystems • Sustainable ecotourism • Golden Gate Park in San Francisco 9-6 How Can We Help to Sustain Aquatic Biodiversity? • Concept 9-6 We can help to sustain aquatic biodiversity by establishing protected sanctuaries, managing coastal development, reducing water pollution, and preventing overfishing. Impacts on Aquatic Ecosystems (1) • Destroyed or degraded by human activities • Coastal habitats disappearing 2-10 times faster than tropical forest • Rising sea levels will destroy coral reefs and some low islands • Ocean floor degradation 150 times larger than area clear-cut annually Impacts on Aquatic Ecosystems (2) • Freshwater habitat disruption – Dams – Water withdrawals from rivers • Likely extinction – 34% marine fish species – 71% freshwater species – Greater than any other group of species Overfishing • • • • Fishery Fishprint 157% overfishing 90% of large open-ocean fishes have disappeared since 1950 Case Study: Industrial Fish Harvesting Methods • • • • Trawler fishing Purse-seine fishing Longlining Drift-net fishing Why Is Protection of Marine Biodiversity So Difficult? • Human aquatic ecological footprint expanding • Not visible to most people • Viewed as an inexhaustible resource • Most ocean areas outside jurisdiction of a country Solutions for Marine Ecosystems • Protect endangered and threatened species • Establish protected marine sanctuaries • Marine reserves – work well and quickly • Integrated coastal management • Protect existing coastal wetlands Three Big Ideas from This Chapter - #1 The economic values of the important ecological services provided by the world’s ecosystems need to be included in the prices of goods and services. Three Big Ideas from This Chapter - #2 We can sustain terrestrial biodiversity by protecting severely threatened areas, restoring damaged ecosystems, and sharing with other species much of the land we dominate.