Human Impacts on Ecosystem (Part 2) Lesson 13

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

  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

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

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

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

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

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

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

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