SE5 Investigate human impact on ecosystems

Suggested time: 3-5 hours

Learning Objectives

1. Explain why ecosystems with similar characteristics can exist in different geographical locations. (CCT)
   
2. Compare a natural and a disturbed (altered) ecosystem and suggest ways of assuring their sustainability.
   
3. Explain why different ecosystems respond differently to short-term stresses and long-term changes.
   
4. Compare the risks and benefits to society and the environment of applying scientific knowledge or introducing a technology . (TL)
   
5. Propose a course of action on social issues related to sustainability, taking into account human and environmental needs. (IL, PSD, TL)
   
6. Predict the personal, social, and environmental consequences of a proposed action. (PSD)
   
7. Defend a decision or judgement and demonstrate that relevant arguments can arise from different perspectives. (CCT, COM)
   
8. Describe how Canadian research projects in science and technology are funded. (TL)
   

Key Questions

1. How do human actions impact ecosystems?
   
2. What are examples of short-term and long-term stresses on an ecosystem?
   

Key Concepts

• Scientific and technological developments impact every person's life. Some effects are desirable; some are not.
  
• Applications of scientific knowledge and technological products and practices are ultimately determined by society. Scientists and technologists have a responsibility to inform the public of the possible consequences of such applications.
  
• The selection of problems investigated by scientific and technological research is influenced by the needs, interests, and financial support of society.
  

Pre-Instructional Questions

1. Do students know the difference between a disturbed or altered ecosystem and a natural ecosystem?
   
2. Can the students identify human activities that affect ecosystems?
   
3. Do students understand how private companies, and non-governmental and governmental agencies fund scientific research?
   

Suggested Teaching Strategies and Activities

1. Students could prepare a case study of an ecosystem that addresses the characteristics of the ecosystem and how it has changed over time. Such a case study should include information that relates to the major concepts studied in this unit - biodiversity, population dynamics, and the cycles of matter. The case study should extend beyond a written description and include data, graphs, and photographs that show evidence of change in the ecosystem. Students could incorporate predictions of future changes to the ecosystem as part of their case study. (COM)
   
   
2. Students could identify examples of ecosystems that have similar characteristics but that exist in different locations across Canada . Students should be able to provide explanations for why these ecosystems can exist in different physical locations. Such explanations should include analysis of biotic and abiotic factors in the ecosystem.
   
   
3. Students should research the ways in which humans have disturbed or altered a specific ecosystem. Students might focus on one particular action within an ecosystem or on multiple actions within the same ecosystem. Examples of human actions to consider include: transportation (e.g., burning fossil fuels or building roads, pipelines, electrical transmission lines), urban development, habitat destruction (e.g., burning forests, draining wetlands, damming waterways, polluting), hunting, poaching, re-locating species, introducing domesticated species into an area, agriculture, forestry, and mining. Students should identify the outcomes of the changes on biotic and abiotic factors in the ecosystem and the overall sustainability of the ecosystem. Students should recognize that society's needs and functions, as well as the global economy, affect one's community. (CD 6.3)
   
   
4. Students should discuss the limits of science in influencing peoples' attitudes and behaviour. Students should consider whether they intend to change their behaviours as they learn more about the effect of humans on their local ecosystems. Students should also consider how they might influence others (e.g., friends, family, community members, politicians) to change their behaviours. (CCT, PSD)
   
   
5. Students could engage in an action project to address an issue of sustainability that is relevant to their local community. Examples of such approaches are identified in materials from Learning for a Sustainable Future ( www.lsf-lst.ca ).
   
   
6. Students could research the role of federal and provincial governmental agencies, universities, environmental groups, tourism groups, and other organizations in funding scientific research related to the environment. Students might investigate issues such as: why these groups fund research, what they hope to learn as a result of the research, how they disseminate their research, where they conduct research, and how much money is spent on environment-related research in Canada. (IL, PSD)
   
   
7. Students could explore the opportunities and trends in occupations related to environmental studies and management, and reflect on how societal knowledge and attitudes drive these employment trends. ( SaskNetWork.ca provides information specific to careers in Saskatchewan .) (CD 6.3)
   
   
8. Students should identify an issue of concern related to sustainability and begin to identify possible solutions. Students could take part in a public deliberation or debate about the issue, or develop and implement an action plan. Many of the illustrative examples listed below might be considered controversial in some communities. Teachers should not shy away from such topics but should make parents aware of the topics that their children may be studying. Teachers should also encourage students to use local resource people as a source of information when researching these topics. Students should be prepared to address social, economic, environmental, political, and technological perspectives when researching these issues. Example topics include:
   
   • Consumers throw away hundreds of billions of plastic shopping bags each year. Plastic bags do require less energy to produce and generate less air pollution and solid waste than paper bags. However, those that are not recycled or buried in landfills may choke birds and clog gutters and sewers. In addition, plastic bag production requires oil and other non-renewable energy sources.
     
   • Farmers often clear wetlands and wooded areas to increase the amount of land available for crops or ranch land. One result of this approach is a reduction in the amount of natural habitat for animal species. How can their practices change to enhance the sustainability of their entire ecosystem without dramatically affecting their economic well-being?
     
   • Producing a single 32MB computer chip requires at least 72 grams of chemicals, 700 grams of elemental gases, 32,000 grams of water, and 1,200 grams of fossil fuels. Production facilities generate huge volumes of toxic chemical waste. How should this waste be handled?
     
   • The ubiquity of cell phones has led to millions of cell phones being discarded in landfills throughout the world. These phones contain lead and non-degradable plastics. Hundreds of thousands of kilograms of lead may leach into the water supply and contaminate this portion of the nutrient cycle. What can people do to eliminate or reduce this problem?
     
   • The suppression of forest fires close to urban areas has led to a build-up of material on the forest floor. In the past, this build-up burned away in natural fires. Now, there are fewer fires but the ones that do occur are more devastating, primarily because they have more fuel to burn. How should provincial forestry agencies use controlled burns to manage forest ecosystems?
     
   • Many city lawns are heavily watered and fertilized in order to maintain a lush look and feel. The grasses used on these lawns may have been introduced to the region from other parts of the country or from other countries. In response, some citizens have planted indigenous grasses, plants, and flowers that require little maintenance or watering. How much freedoms should landowners be given in order to maintain their yard in any way that they choose?
     
   • Nitrate poisoning can occur in cattle raised in the Prairies because microbes in the digestive tract favour the conversion of nitrate to nitrite. Poisoning is usually associated with animals ingesting forage or feed with a high nitrate content. If cattle rapidly ingest large quantities of plants that contain high levels of nitrate, nitrite will accumulate in the rumen. This problem did not exist until the development of nitrate-based fertilizers in the early part of the 20^th century. Each year, more and more nitrate-based fertilizers are applied to crops in the Prairies. Can farming practices change to reduce this problem without creating other problems in the ecosystem?
     
   • A second problem related to the use of nitrate-based fertilizer use is the build-up of nitrates in water supplies. Plants are only able to absorb a certain amount of the nitrogen from fertilizer. Excess nitrogen often washes away into surface and groundwater systems where it becomes more concentrated. Discuss the impacts of increased nitrogen build-up on biotic and abiotic components of aquatic or terrestrial ecosystems.
     
   • The global transportation of products influences the balance of energy in nutrient cycles by moving the finished products away from their sources. As a result, the environment that contains the finished product may not be able to effectively use the energy available in the product. Consider a typical Prairie house that contains many wood products. Abandoned houses in rural settings may naturally decay over many years, returning the energy stored in the wood back to the ecosystem. In a city, older houses are typically demolished and the wood products transported to a landfill where they may never decay. What actions can individuals or communities take to help restore this balance of energy?
     
   • People who live in larger communities generally rely on others to provide them with clean, safe drinking water. Typically, governmental agencies regulate the procedures for municipal water and sewage treatment that includes physical, chemical, and biological methods of removing pollutants. What can an individual do to reduce the need for more technologically advanced systems of treating our water?
     
   • The primary logging practice throughout North America for most of the 20^th century was clear-cutting where all trees and undergrowth are removed from a large area at once. There has been a shift away from clear-cutting, even though it appears to be economical on a large scale, towards selective cutting in which loggers harvest only the best trees. Should there be a ban on clear-cutting in all circumstances and locations?
     
   • Organic approaches to farming attempt to use the natural characteristics of plants, insects, and animals to grow vegetable and cereal crops that are free of disease. Modern North American agricultural practice uses a monoculture approach which requires the use of herbicides and pesticides to support the growth of a single crop on a large scale. Compare and contrast these approaches, their consequent effects on biodiversity, and their vulnerability to environmental changes.
     
   • Many areas of the Prairies are experiencing an overabundance of deer as a result of decreases in natural predators such as wolves, bears, and lynx and restrictions on hunting. The deer feed on crops, lawns, and gardens that were not planted for that purpose. Is hunting an appropriate method of attempting to control populations that humans perceive as annoyances? Is re-introducing natural predators such as the grey wolf a better alternative?
     
   • Some scientists believe that the human population may have grown beyond the Earth's carrying capacity, given that our actions have used up most of the original biomass of the Earth. Other scientists believe that advances in technology are able to increase the Earth's carrying capacity. How does the human ability to disrupt the flow of energy and matter through ecosystems affect the sustainability of the entire planet?
     
   • As of mid 2005, the world's human population is growing at a rate of 200,000 new people each day. Is this growth sustainable given that there are essentially no new unoccupied lands for people to pioneer, as was true up until the 20^th century?