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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 http://www.greenbeltmovement.org/ Watch second video 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: uncut or regenerated primary forest that has not been seriously disturbed by human activities or natural disasters for several hundred years or more • Second-growth forests: a stand of trees resulting from secondary ecological succession. Develop after trees have been removed by human activities such as clear cutting for timber or cropland or by natural forces such as fire, hurricanes, or volcanic eruption • Tree plantation; tree farm; commercial forest Old growth forest in the US state of Washington’s Olympic National Forest Fig. 9-2, p. 180 Short (25- to 30- year rotation cycle of cutting and regrowth of a monoculture tree plantation in modern industrial forestry. In tropical countries, trees grow more rapidly year round so rotation cycle can be 6-10 years. Fig. 9-3, p. 180 Old growth or second growth forest are clear cut to provide land for growing most tree plantations Fig. 9-3, p. 180 pFigure 9.4: Major ecological and economic services provided by forests (Concept 9-1). Question: Which two ecological services and which two economic services do you think are the most important? ital Forests Ecological Services Economic Services Support energy flow and chemical cycling Fuelwood Reduce soil erosion Lumber Absorb and release water Pulp to make paper Purify water and air Mining Influence local and regional climate Livestock grazing Store atmospheric carbon Recreation Provide numerous wildlife habitats Jobs Fig. 9-4, p. 181 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 • This is hundreds of times the economic value • Need to start factoring values into land use • Ecological services can be a sustainable source of ecological income Estimated annual global economic values of some ecological services provided by forests compared to the raw materials they produce (in billions of dollars). Fig. 9-A, p. 181 Harvest Methods • Step one: build roads – Erosion – Invasive species – Open up for human invasion • Step two: logging operations – Selective cutting: intermediate aged or mature trees in an uneven aged forest are cut singly or in small groups (Fig 9-6a) – Clear cutting: remove all the trees from an area – Strip cutting: involves clear cutting a strip of trees along the contour of the land within a corridor narrow enough the allow natural regeneration within a few years Cleared plots New highway for grazing Cleared plots for agriculture Highway Old growth Fig. 9-5, p. 182 Major tree harvesting methods. If you were cutting trees in a forest you owned which method would you choose and why? (a) Selective cutting Clear stream Fig. 9-6, p. 182 (b) Clear-cutting Muddy stream Fig. 9-6, p. 182 (c) Strip cutting Uncut Cut 1 year ago Dirt road Cut 3–10 years ago Uncut Clear stream Fig. 9-6, p. 182 Clear cut logging in the US state of Washington Fig. 9-7, p. 182 Forests and Fires • Surface fires – Burn only undergrowth and leaf litter – May kill seedlings and small trees but spare most mature trees; allow most wild animals to escape – Cool fire – Ecological benefits: help prevent more destructive fires, free mineral nutrients, release certain seeds and stimulate germination of some tree seeds, help control diseases and insects • Crown fires – Burn the entire tree – Hot fire – Occur in forests with lack of surface fires Type of fire? Fig. 9-8, p. 183 Type of fire? Fig. 9-8, p. 183 Loss of Original Forests • Deforestation • Over past 8,000 years, human activities have reduced the earth’s forest by 46%, most of this loss since since 1950 • Most in tropical areas, developing countries • Estimated loss of 40% intact forests within next 20 years Extreme tropical deforestation in Chiang Mai,Thailand. What do you think will happen to the dried out topsoil when the winds come? How does the term ecological tipping point apply here? Fig. 9-9, p. 184 Fig. 9-10, p. 184 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 Natural Capital Degradation Major Causes of the Destruction and Degradation of Tropical Forests Basic Causes Secondary Causes • Not valuing ecological services • Roads • Cattle ranching • Crop and timber exports • Fires • Logging • Government policies • Settler farming • Tree plantations • Poverty • Cash crops • Population growth Tree plantations Cattle ranching Logging Cash crops Settler farming Fires Roads Fig. 9-11, p. 186 Brazil’s Amazon basin What’s going on in this picture? Fig. 9-12, p. 187 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. Fig. 9-13, p. 188 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 Kenaf Fig. 9-14, p. 189 Ways to Reduce Tropical Deforestation • • • • Debt-for-nature swaps Conservation concessions Gentler logging methods Encourage use of wood substitutes Solutions Sustaining Tropical Forests Prevention Restoration Protect the most diverse and endangered areas Encourage regrowth through secondary succession Educate settlers about sustainable agriculture and forestry Subsidize only sustainable forest use Protect forests with debt-for-nature swaps and conservation concessions Rehabilitate degraded areas Certify sustainably grown timber Reduce poverty Slow population growth Concentrate farming and ranching in already-cleared areas Fig. 9-15, p. 190 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 What happens to overgrazed rangeland? Fig. 9-16, p. 191 Manage Rangelands Sustainably • Practice rotational grazing • Fence out riparian zone areas • Suppress invader plants – Herbicides – Mechanical removal – Controlled burning – Short-term trampling Fig. 9-17, p. 191 Fig. 9-17, p. 191 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 The Gray Wolf and Yellowstone National Park Fig. 9-B, p. 193 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 Costa Rica Panama Pacific Ocean National parkland Buffer zone Fig. 9-18, p. 194 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 34 biodiversity hotspots identified by ecologists as important and endangered centers of terrestrial biodiversity that contain a large number of species found nowhere else. Identifying and saving these critical habitats requires a vital emergency response. Fig. 9-19, p. 196 Supplement 4, Fig. 2, p. S16 Ecological Restoration • Restoration: returning a particular degraded habitat or ecosystem to a condition as similar as possible to its natural state • Rehabilitation: turning a degraded ecosystem into a functional or useful ecosystem without trying to restore it to its original condition ex. Removing pollutants and replanting to reduce soil erosion in abandoned mining sites • Replacement: replacing a degraded ecosystem with another type of ecosystem ex. A degraded forest could be replaced by a pasture or tree plantation • Creating artificial ecosystems: ex. Creating artificial wetlands to help reduce flooding or treat sewage 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 Fig. 9-20, p. 198 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 Area of ocean bottom before a trawler net scraped it like a gigantic plow. Fig. 9-21, p. 199 The same area after the trawler scraped the ocean bottom. According to marine biologist Ellie Norse, “Bottom trawling is probably the largest human-caused disturbance to the biosphere.” Trawler fishers disagree and claim that the ocean bottom life recovers after trawling. Fig. 9-21, p. 199 Overfishing • • • • Fishery Fishprint 157% overfishing 90% of large open-ocean fishes have disappeared since 1950 Collapse of Canada’s 500 year old Atlantic cod fishery off coast of Newfoundland Fig. 9-22, p. 200 Case Study: Industrial Fish Harvesting Methods • • • • Trawler fishing Purse-seine fishing Longlining Drift-net fishing Major commercial fishing methods Fish farming in cage Trawler fishing Spotter airplane Sonar Purse-seine fishing Drift-net fishing Long line fishing Float Buoy lines with hooks Deep sea aquaculture cage Fish caught by gills Fig. 9-23, p. 201 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 Solutions Managing Fisheries Fishery Regulations Bycatch Set catch limits well below the maximum sustainable yield Use wide-meshed nets to allow escape of smaller fish Improve monitoring and enforcement of regulations Use net escape devices for seabirds and sea turtles Economic Approaches Ban throwing edible and marketable fish back into the sea Sharply reduce or eliminate fishing subsidies Charge fees for harvesting fish and shellfish from publicly owned offshore waters Aquaculture Certify sustainable fisheries Control pollution more strictly Protect Areas Restrict coastal locations for fish farms Establish no-fishing areas Depend more on herbivorous fish species Establish more marine protected areas Nonnative Invasions Rely more on integrated coastal management Kill organisms in ship ballast water Consumer Information Label sustainably harvested fish Filter organisms from ship ballast water Publicize overfished and threatened species Dump ballast water far at sea and replace with deep-sea water Fig. 9-24, p. 202 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. Three Big Ideas from This Chapter - #3 We can sustain aquatic biodiversity by establishing protected sanctuaries, managing coastal development, reducing water pollution, and preventing overfishing.