1. Human Impacts on Ecosystem (Part 2)
Lesson 13

2. Forestry Practices
natural forest ecosystems provide us with valuable resources
Canada is a large source of wood
Approximate 60% of our original forests have been cut at least once

3. Clear-cutting
Shelterwood cutting
Selective cutting
What is it?
Removal of all or most of the trees in an area
Mature trees are left standing to provide shelter for the new growth
Selected trees are harvested
Advantages
-least expensive
-quickest
-allows for new growth
-mimics fire patterns
- not all trees in an area are cut down
-has the least impact on the ecosystem
Disadvantages
-has the greatest impact on the ecosystem
-soil is washed or blown away
-soil health suffers
-the area is not cleared for new growth
-the most expensive method

4. 90% of trees harvested in Canada are through clear-cutting
It is important to have practices that keep the forests as sustainable as possible

5. Stewardship: taking responsibility for managing and protecting the environment
If we take a resource from the ecosystem, we must accept the responsibility for keeping the ecosystem healthy
With stewardship of earth’s resources, we can live in harmony with the ecosystems that we rely on

6. Problem with Pesticides
Pesticides: A substance used to kill a pest
e.g. Herbicides kill plants, insecticides kill insects, fungicides kill fungi

7. a) Pollution
Some pesticides are sprayed and may cause air, soil, or water pollution
b) Non-Target Organisms
Pesticides can harm organisms that are not the intended target

8. c) Bioaccumulation
Some pesticides build up in the bodies of individual organisms
Bioaccumulation occurs when a pesticide cannot dissolved in water, but does dissolve in fats and oils

9. d) Bioamplification
Remember all individuals in an ecosystem are a part of a food chain
Toxins stored in an organism at one trophic level are passed on to the organisms at the next tropic level
Pesticides become more concentrated as they move up the food chain

10. e) Resistance to Pesticides
Species may become resistance to it when a pesticide is used for a long period of time
Farmer needs to apply more pesticide or a stronger pesticide to control the pests