Lecture 25 Fall04

Lecture 25 Fall04 - Lecture 25: Environmental Impact of...

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Unformatted text preview: Lecture 25: Environmental Impact of Lecture 25: Environmental Impact of Agriculture and World Food Issues Agriculture and World Food Issues I. Environmental impact of agriculture Declining biodiversity Soil erosion Salinization Desertification Chemical fertilizers Pesticides II. World food issues Introduction Current agricultural practices are aimed at increasing and maximizing yields: ________________ bred for high yield, easier harvesting _______________ use of chemical fertilizers to nourish the crops _______________ use of chemical pesticides to control pests and increase yields _____________ chemical herbicides to kill off weeds The Green Revolution The Green Revolution the introduction of scientifically developed food crops that can produce _________ yields, under conditions of high inputs of water, fertilizers and pesticides. The Green Revolution saved millions of people from starvation in developing countries... But with serious ___________________ consequences! These practices deplete and destroy future capacity to produce food. I. Environmental impact of agriculture Six environmental problems created by current agricultural practices 1. Declining _______________ 2. Soil _________________ 3. Soil _________________ 4. Desertification 5. Chemical fertilizer pollution 6. Pesticide/herbicide pollution Well also look at some solutions to these problems 1. Declining biodiversity Seed companies focus on a few varieties for farmers (high yielding, easier to harvest, resistant to disease) Putting all your eggs in one basket Out of 30,000 __________ plants, only _____ are major sources of food in the world Wild populations have greater genetic ________ This contributes to a populations long-term survival (_____________ = adapting to changing conditions) Domesticated crops Domesticated crops have much ________ genetic diversity Selective breeding results in crop uniformity (traits may be lost) Lower genetic diversity => likely for crop to succumb to unexpected stresses (new diseases, pests, drought, flooding, high UV, etc) _________ evolve much more rapidly Uniform domesticated populations are ________ vulnerable New diseases dont hurt wild populations as much, because of genetic diversity 2. Soil erosion Loss of soil comes from ___________ (plowing) the land and the effects of wind and water Soil is made of organic and inorganic matter ____________ matter gives texture (for root growth) and feeds microorganisms that plants need Topsoil is richest in organic matter Problems: Soil erodes at about 18 to 100 metric tons per hectare per year Soil forms about 1 metric ton per hectare per year Topsoil is lost (it contains ______________, etc.) Subsoil is left after erosion: it contains less nutrients, minerals, holds less water its like concrete! Solutions to prevent soil erosion...
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Lecture 25 Fall04 - Lecture 25: Environmental Impact of...

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