Transcript File
Chapter 3.2 Forests and Fisheries Pre-Chapter Activity What happened to the Tuna? Forest Resources Forest provides many valuable resources: -maple syrup -rubber -nuts -wood pulp for making paper -construction and paper -furniture -oxygen for people -prevent flooding and control soil erosion What are some of the things made from trees in this classroom? • • • • • • • Writing paper Cardboard Poster board Toilet paper Textbooks Furniture Pencils Managing Forests • There are 300 million hectares of forest in USA. • 1 million of people work for the forest industry • Because new trees can be planted or replaced trees that are cut down, forests can be renewable resources. Logging Methods 2 methods of logging: 1. Clear cutting 2. Selective cutting 1. Clear-cutting method • Cutting down all the trees in an area at once. • Advantages: faster and cheaper; safer for loggers • Disadvantages: more damages to forests; ecosystem changes, the soil is exposed to wind and rain, and can be blown away or washed away. Clear-cut forest 2. Selective cutting method • Is cutting some trees in a forest and leaving a mix of tree sizes and species behind. • Advantages: less damaging to forest • Disadvantages: loggers must move their heavy equipment around the forest Selective cut forest Sustainable forestry • Forests should provide a sustainable yield which is an amount of renewable resource such as trees that can be harvested regularly without reducing the future supply. • # Cut trees = # of planted trees Certified Wood The Forest Stewardship Council is an international organization dedicated to sustainable forest management. The certify forests that are well managed and provide good working conditions for workers. Fisheries • Is an area with a large population of marine organisms. • They are valuable renewable resources. • In the past, there were so many fish to catch. Over time, the population of fish declined. WHY??? WHY??? What happened? The fish were caught faster than they could breed, so the population decreased. This is called “overfishing.” Managing fisheries for a sustainable yield includes: 1. Setting fishing limits 2. Changing fishing methods 3. Developing aquaculture techniques 4. Finding new resources 1. Fishing Limits • Laws can ban fishing of certain species. • Laws can limit the number or size of fish or require that fish be in a specific size range. • Laws want to make sure that fish survive long enough to reproduce and that not all of the largest adult fish aren’t caught. 2. Fishing Methods • Today many fishermen catch fish with nets with a larger mesh size that allow small young fish to escape. • Some fishing method are controlled by laws. Some of them are old; like the one that allows poison fish with cyanide and stunning them with dynamite under water. These methods hurt all the fish in an area rather than targeting certain fish. 3. Aquaculture • Is a practice of raising fish for food in artificial ponds or bays (ex. salmon, catfish, shrimp) • Disadvantages: replace natural habitats; cause pollution and spread diseases into wild fish population 4. New Resources -9,000 different fish species are caught for food -one way is to help feed a growing human population is to fish for a new species such as monkfish, tile fish and tilapia. Questions: Why is forests important? What is a sustainable yield? What is aquaculture? How can setting limits on the size of fish that can be caught help maintain fish populations? What steps do you think scientists might take to convince the public to eat different species of fish? Ch 2.3 Assessment 1a. Why are forests considered renewable resource? 1b. How does the clear-cutting logging method differ from selective cutting? 1c. You are walking in a clear-cut section of forest a few days after a heavy rainstorm. A nearby stream is very muddy and has many dead fish. What might have happened? Ch 3.2 Assessment (con’t.) 2a. What are four ways fisheries can be managed for a sustainable yield? 2b. What are two kinds of laws that regulate fishing? How can they help ensure the health of a fishery? 2c. What might happen to a fish population over time if all the largest fish in the population were caught? Explain.