CHAPTER 13 Restoration Ecology

Transcription

1 CHAPTER 13 Restoration Ecology 85 Chapter Objectives Illustrate the ways that we can help nature heal. Show how nature is resilient. Explain how restoring forests has benefits. Summarize plans to restore prairies. Compare approaches to restoring wetlands and streams. Key Terms Intervention Mitigation Reallocation Reclamation Re-creation Rehabilitation Remediation Restoration Concept Review 13.1 Helping Nature Heal Humans have disturbed and degraded nature as long as we ve existed. However, we are able to repair some of the damage we ve caused. This relatively new field is called ecological restoration. Recovery is linked to the idea that if we leave nature alone it will eventually return to the natural climax community. Modern ecology has shown that this may not be the case and is a random process Many research ecologists point out that the aims of restoration often are driven by human values, such as beauty, recreation, utility, and other social or philosophical issues rather than pure science General principles in restoration are drawn from many sciences such as ecology, hydrology, soil science, etc. The most influential American forester was Gifford Pinchot. He introduced a system of selective harvest and replanting of choice tree species that increased the value of the forest while also producing a sustainable harvest of trees. Pinchot became the first head of the U.S. Forest Service. Another pioneer in restoration ecology was Aldo Leopold. He is known as a visionary pioneer and an important figure in conservation history.

2 Nature Can Be Remarkably Resilient The first step in conservation and ecological restoration is generally to stop whatever is causing damage. For example, prohibiting logging, mining, or excessive burning may be enough to allow nature to heal by itself. Sometimes rebuilding populations of native plants and animals is a simple process of restocking breeding individuals to an area Restoring Forests Has Many Benefits Lumber companies routinely replant forests they have harvested to prepare a future crop. Seedlings are grown in nurseries, and tractor drawn planters allow a team of workers to plant thousands of new trees per day. This mechanical reforestation results in a monoculture of uniformly spaced trees that have little resemblance to diverse, complex native forests. However, they do supply ground cover, provide habitat for some wildlife species, and grow valuable lumber for paper pulp. Japan was almost completely deforested at the end of World War II, but in the 60 years since then, Japan has carried out a massive reforestation program. Now, more than 60 percent of the country is forest-covered. The biggest reforestation project in history is now taking place in China, where at least a billion people have planted 50 billion trees over the past 30 years to create a green wall to hold back the deserts. This effort has been intensified recently to help clean the air before the 2008 Olympics. Planting trees within cities can be effective in improving air quality, providing shade, and making urban environments more pleasant. In 2007, the United Nations announced a billion tree campaign that hopes to gather pledges to plant one billion new trees around the world. Historically, fire was important in controlling vegetation in savannas. When settlers eliminated fire and grazing by native animals, savannas were invaded by a jumble of shrub and tree growth. Now, accumulated vegetation and fuel are cleared before fires are started, and herbicide treatment may be necessary to prevent regrowth of invasive species until native vegetation can become established. Many national parks now recognize the necessity for fire to maintain forests. Seventy years of fire suppression in Sequoia National Park allowed dense undergrowth that crowded around the base of the sequoias. These smaller trees allowed a ladder for fire to climb up the trees and

3 kill them. Fuel removal and periodic prescribed fires are now a regular management tool for protecting the giant trees Restoring Prairies Before European settlement, prairies covered most of the middle third of what is now the United States. Tallgrass prairies covered the eastern edge of the Great Plains. This prairie has almost entirely disappeared, having been plowed and converted to corn and soybean fields. Less than 2 percent of the original prairie remains in its original condition. Fire is also crucial for prairie restoration because it kills many weedy species and, also removes nutrients (especially nitrogen). This gives native species, which are adapted to low-nitrogen soils, an advantage. The Nature Conservancy has established many preserves throughout the eastern Great Plains to protect fragments of tallgrass prairie. Huge areas of shortgrass prairie are being preserved. Bison help maintain prairies and, together with fire, are considered important tools in prairie restoration Restoring Wetlands and Streams Although wetlands currently occupy less than 5 percent of the land in the United States, the Fish and Wildlife Service estimates that onethird of all endangered species spend at least part of their lives in wetlands. Until recently, federal, state, and local governments encouraged wetland drainage and filling to create land for development. The 1972 Clean Water Act began protecting streams and wetlands by requiring discharge permits for dumping waste into surface waters. For wetlands, sometimes all that s needed is to stop the destructive forces. This might mean to restore water supplies that have been diverted elsewhere. The Everglades is a river of fresh water that comes from springs near Orlando and moves through Lake Okeechobee southward to the Gulf. This has been diverted, causing 90 percent of wading birds to be lost; many are worried that the entire aquatic ecosystem may be collapsing. It is hoped that by simply restoring the former flow to the Everglades that this will allow the biological community to recover. The Chesapeake Bay is a drowned river valley with fresh water flowing south and saltier water flowing north. Tides and currents mix this water, distributing nutrients and flushing out wastes. Overfishing, sewage discharge, silt from erosion, heavy metals, toxic chemicals, and heat from industry, pesticides, and herbicides from

4 88 agricultural runoff, oil spills, and habitat destruction is causing a loss of productive fisheries in the area. Restoration efforts in the Chesapeake Bay are having minimal success, but maybe someday the area may be a productive, healthy ecosystem. Many cities are finding that artificial wetlands provide a low-cost way to filter and treat sewage effluent. Stabilizing stream banks, stopping pollution, controlling invasive organisms, preventing erosion are restoring streams and other human caused problems are repairing streams that have been damaged. Remediation means finding remedies from problems involving noninvasive techniques. Reclamation implies using intense physical or chemical methods to clean and repair ecosystems. Class Time: The Acorn outline suggests 5-10 percent of the course include habitat loss, overuse, pollution, introduced species, maintenance through conservation, management of wilderness areas, national parks, wildlife refuges, forests, and wetlands. Plan to spend 3-5 days to cover the material presented in this chapter. Approach and Tips Begin by having the students describe what the habitat they live in was like 20, 50, and 100 years ago. Some research may be needed to determine what changes have taken place; others may have not experienced as much change, depending upon their location. Discuss the role of ecosystem management in preserving habitat and how developers in your area succeeded or failed according to the student s viewpoint. You may want to assign specific national parks or refuges for students to research, or have them research the roles of the U.S. Forest Service or National Park Service to determine what students may view as the conflicts of interest that occur with multiple use contracts (for example, logging in national forests). The portions of the chapter that deal with remediation and the importance of wetlands should be given additional emphasis at some point during the course. You may choose to include this discussion when you cover water pollution and the students have more background information to refer to. Have students design an experiment examining habitat fragmentation or reduction. Commonly used organisms include land snails, crickets, mealworms, and daphnia.

5 Applications 89 Ecotourism Brochure Lab Objective: To learn ways that we can help nature heal and show that restoring ecosystems has benefits. Materials: construction paper, Internet access or the library, markers Procedure: 1. Assign each group of two to four students an area that needs restoration. Ex. Forests (Costa Rica, National Parks, Japan after WWII, etc.), prairies (Great Plains), wetlands and streams (Everglades, Chesapeake Bay), Great Barrier Reef. 2. Have each group design a tri-fold ecotourism travel brochure. The idea is to include information on how their company is restoring this ecosystem and why tourists would want to visit and hire this company to take them on the trip. 3. Information that should be included in the brochure: Conclusion: a. Why is this environment important? b. What is being done to restore this habitat? c. Are noninvasive species a problem and, if so, how are these being addressed? d. What percentage of the natural environment is left? e. What caused the destruction of this habitat in the first place? f. A map of the area should be included. g. List some native species that inhabit this environment. h. What are some things that the travelers can do to help? i. What are the unique characteristics of this area? j. From an environmental perspective, why should we care what happens to this environment? k. Be sure to include your company s name, phone number, price of the trip, and what all is included. Have students answer the following questions on a separate sheet of paper. 1. What if you are so successful that too many people want to visit your ecosystem? What might happen to the area? Can you think of examples of where this has happened in the real world? 2. When might Ecotourism not be an ideal strategy for conservation?

6 Common Mistakes and Misconceptions 90 How clean is clean enough? Many students are under the impression that in order to clean up an ecosystem we must get it 100% clean. Most of the time this is impossible. Economic concepts come into play as well as the damage that might be done to the environment in staying around to clean the area. A good way to explain this is the Exxon Valdez oil spill. Exxon had to decide at some point that they had cleaned as much as they could. When is it clean enough? Must Exxon get every last drop of oil off the bottom of every rock? Once they had cleaned the water, the beaches and the area until they were restored to 90%, is that good? What about 80%? Each decision must be made considering the area, the economics, and the harm to the environment that is incurred by staying around to clean anymore. For example, could the $50 million dollars needed to clean the underside of each pebble on an oil covered beach be put to better use conserving some other part of the environment? Suggested Website For more information on the Exxon Valdez disaster, go to Questions 1. Compare and contrast the four aspects of restoration ecology: rehabilitation, remediation, reclamation, and re-creation. Discuss what human activities would have caused the disturbances in each case. 2. Explain why maintaining biological diversity is a key component of ecosystem management. Give an example of a keystone species in a particular ecosystem, and discuss its importance. 3. For many years, the U.S. Forest Service suppressed fires in national forest lands by removing brush and other vegetation. More recently, using adaptive management practices, vegetation is not cleared and fires are allowed to burn (to an extent) in order to rejuvenate the ecosystem. Explain why this is a controversial practice and how this is considered an adaptive management practice.