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Sustaining Biodiversity: The Ecosystem Approach
Chapter 9
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Types of Forests Old-growth- not seriously disrupted for at least several hundred years Second-growth - results from secondary succession Tree plantation or tree farm - managed tract of uniformly aged trees of one or two species. Clear cut when commercially valuable, then replanted.
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Major Services of Forests
Natural Capital Ecological services of world’s forests valued at $4.7 trillion per year Forests Value of ecological services much greater than value of economic services Ecological Services >>> Much greater than Economic Services Support energy flow and chemical cycling Reduce soil erosion Absorb and release water Purify water Purify air Influence local and regional climate Store atmospheric carbon Provide numerous wildlife habitats Fuelwood Lumber Pulp to make paper Mining Livestock grazing Recreation Jobs Fig. 9-4, p. 181
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Types of Forest Management
Even-aged management (= industry forestry) trees about same age and size- simplified tree plantation- 1-2 fast-growing species harvested on rotation cycle Rotation cycles: years (temperate), 6-10 years (tropical) Uneven-aged management- variety of species w/ range of ages & sizes. Goals: biodiversity, sustainable high quality timber Sustainable management intensive management of as little as 20% of world’s forests could meet current and future demand for commercial wood / fiber
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Tree Plantation
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Management Strategies: Rotation Cycles
Weak trees removed Seedlings planted Clear cut 25 15 10 30 Years of growth 5 Growth faster in tropical countries (6-10 years)
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Degradation of Forests from Logging Roads
Increased erosion and sediment runoff Habitat fragmentation Biodiversity loss Pathways for pests, diseases, and invasive species More accessible for humans
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Degradation of Forests
Highway Old growth
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Degradation of Forests
Cleared plots for grazing Highway Cleared plots for agriculture
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Degradation from Clear-cut Logging
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Tradeoffs of Clear-cutting Forests
Advantages Disadvantages Higher timber yields Maximum economic return in shortest time Can reforest with genetically improved fast-growing trees Short time to establish new stand of trees Needs less skill and planning Best way to harvest tree plantations Good for tree species needing full or moderate sunlight for growth Reduces biodiversity Disrupts ecosystem processes Destroys and fragments some wildlife habitats Leaves moderate to large openings Increases soil erosion Increases sediment water pollution and flooding when done on steep slopes Eliminates most recreational value for several decades
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Harmful Effects of Deforestation
© 2006 Brooks/Cole - Thomson Natural Capital Degradation Deforestation Decreased soil fertility from erosion Runoff of eroded soil into aquatic systems Premature extinction of species with specialized niches Loss of habitat for migratory species such as birds and butterflies Regional climate change from extensive clearing Releases CO2 into atmosphere from burning and tree decay Accelerates flooding
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Global Outlook: Extent of Deforestation
Extensive deforestation by humans over past 8,000 years ( % reduction) Deforestation continues Some reforestation in North America and Europe. However, tree plantation ≠ old growth forest Some regrown tropical forests show increased tree cover
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Protecting Tropical Forests
Solutions Sustaining Tropical Forests Prevention Restoration Protect most diverse and endangered areas Educate settlers about sustainable agriculture and forestry Phase out subsidies that encourage unsustainable forest use Add subsidies that encourage sustainable forest use Protect forests with debt-for-nature swaps, conservation easements, and conservation concessions Certify sustainably grown timber Reduce illegal cutting Reduce poverty Slow population growth Reforestation Rehabilitation of degraded areas Concentrate farming and ranching on already-cleared areas
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World’s Forests Deforestation
Economic value of forests: value of ecological services could be as high as $4.7 trillion / year. Value of ecological services >>> economic value Should we make economic estimates? ”Our economic system has been constructed under the premise that natural services are free.” Profits are short term, services long-term Sustainable management of forests Certifying sustainably grown timber 2002 Mitsubishi agreed to certify practices as sustainable (Home Depot & Lowes sell only certified wood)
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Sustainable Forestry Conserves biodiversity, water & soil resources
© 2006 Brooks/Cole - Thomson Solutions Sustainable Forestry Conserves biodiversity, water & soil resources Grow more timber on long rotations Rely more on selective cutting and strip cutting No clear-cutting, seed-tree, or shelterwood cutting on steeply sloped land No fragmentation of remaining large blocks of forest Sharply reduce road building into uncut forest areas Leave most standing dead trees and fallen timber for wildlife habitat and nutrient recycling Certify timber grown by sustainable methods Include ecological services of trees and forests in estimating economic value
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US Forests Reforestation Old-growth forests still decline
Forest fires: surface, crown, and ground
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Surface and Crown Forest Fires
Ground fire = underground surface fire, common in northern peat bogs
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Minimizing Forest Damage from Fire
Prescribed burning- reduce underbrush Allow small fires in National Parks, forests & wilderness to burn (if people & property not threatened) Defensible space- clear 200 feet around buildings Effects of the Healthy Forests Initiative Timber Co. allowed to take large/medium trees in Nat. Forests if they clear away smaller, fire-prone trees- criticized by fire scientists (large tree most fire resistant, logging creates slash)
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Reintroducing Wolves to Yellowstone (1995)
Why wolves were killed- 2 million killed to “make the west safe for livestock and big-game animals” Wolf protection 1974 listed as endangered species Ecological importance- Keystone predator- culled herds of bison, elk, caribou and mule deer, keep coyote pop low, … Yellowstone controversy- ranchers, hunters, miners all opposed Importance of biodiversity- ecological success- willow & aspen re-growth in riparian areas, more beavers, elk carcasses feed grizzlies, coyote population reduced, squirrel & fox pop increase = more food for eagles & hawks
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Establishing, Designing, Protecting Nature Reserves
Currently 12% of earth’s land is “protected” Include large to moderate tracts of land Preserve biodiversity Involve government, businesses, and private groups Buffer zone concept: biosphere reserves Costa Rica’s accomplishments Adaptive ecosystem management Emergency action and biodiversity hot spots Wilderness
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Biosphere Reserve Fig. 8-23, p. 174 Biosphere Reserve Core area
Buffer zone 1 Buffer zone 2 Tourism and education center Human settlements Research station Fig. 8-23, p. 174
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Biodiversity Hot Spots
Fig. 8-26, p. 176
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Types of US Public Lands (35% of US is public land)
Multiple-use lands: National Forest System; Natural Resource Lands (BLM) Moderately restricted-use lands: Natural Wildlife Refuges Restricted-use lands: Natural Park System; Natural Wilderness Preservation System
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US Federal Public Lands
National parks and preserves National forests (and Xs) National wildlife refuges Fig. 8-6b, p. 158
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Logging in U.S. National Forests
Trade-Offs Logging in U.S. National Forests Advantages Disadvantages Helps meet country’s timber needs Cut areas grow back Keeps lumber and paper prices down Provides jobs in nearby communities Promotes economic growth in nearby communities Provides only 4% of timber needs Ample private forest land to meet timber needs Has little effect on timber and paper prices Damages nearby rivers and fisheries *Recreation in national forests provides more local jobs and income for local communities than logging Decreases recreational opportunities
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Kenaf Holds potential to greatly reduce pressure to cut trees for paper
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Ecological Restoration
= “process of repairing damage caused by humans to the biodiversity & dynamics of natural ecosystems” Restoration, rehabilitation and replacement Creating artificial ecosystems 4 Principles of Ecological Restoration: Mimic nature Recreate important ecological niches Rely on pioneer, keystone and foundational species and natural ecological succession Control or remove nonnative species Accomplishments in Costa Rica
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Restoration of a Stream Bank
Area restored in 10 years after banning grazing and off-road vehicles.
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Major Human Impacts on Aquatic Biodiversity
Loss and degradation of habitat is greatest threat Damage to coral reefs and other habitats Dredging / trawler operations destroy bottom habitats Overfishing Premature extinction
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Degradation of the Ocean Floor
Fig. 8-29, p. 179
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Protecting and Sustaining Marine Biodiversity
Protecting endangered and threatened species Establish large and unpolluted protected areas- marine reserves work. Integrated coastal management Protect wetlands Prevent overfishing Regulate and prevent pollution
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Managing Fisheries Fig. 8-30, p. 181 Solutions Managing Fisheries
Fishery Regulations Set catch limits well below the maximum sustainable yield Improve monitoring and enforcement of regulations Economic Approaches Sharply reduce or eliminate fishing subsidies Charge fees for harvesting fish and shellfish from publicly owned offshore waters Certify sustainable fisheries Protected Areas Establish no-fishing areas Establish more marine protected areas Rely more on integrated coastal management Consumer Information Label sustainably harvested fish Publicize overfished and Bycatch Use wide-meshed nets to allow escape of smaller fish Use net escape devices for seabirds and sea turtles Ban throwing edible and marketable fish back into the sea Aquaculture Restrict coastal locations for fish farms Control pollution more strictly Depend more on herbivorous fish species Nonative Invasions Kill organisms in ship ballast water Filter organisms from ship ballast water Dump ballast water far at sea and replace with deep-sea water Fig. 8-30, p. 181
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