geog 5_notes1

geog 5_notes1 - Agro-Ecosystems vs. Natural Ecosystems 1....

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Agro-Ecosystems vs. Natural Ecosystems 1. In farming we try to stop ecological succession & keep the agro-ecosystem in the early stages of succession; maximizes sunlight, water, & nutrients for crops; prevent establishment of shrubs, trees… 2. In farming, monoculture (mono-cropping) is the norm a. Problems of monoculture i. More vulnerable to pests, parasites, fungal attacks ii. Repeatedly planting the same crops can reduce soft fertility 3. Farming greatly simplifies biological diversity 4. Crops are planted in rows, incr’g efficiency but making them more vulnerable to pests a. Plants “hide” too from pests in complex ways making it harder for…? 5. Farming usu involves plowing a. Plowing is unlike any natural disturbance b. Brings nutrients to surface, enhances short-term productivity but ultimately requires the addition of outside nutrients (fertilizers) c. 6. Genetic modification a. In the USA, ¾ of soybeans, 1/3 corn are genetically modified Some Environmental Impacts of Agriculture 1. Soil Erosion a. b. Leads to declining soil fertility c. The natural replacement rate of top soil averages 1 mm every 10-40 yrs d. Since end of WWII, farming has has seriously damaged about 10? 75? 5%?? Of the world’s best soil e. In the US about 1/3 of the best top soil has been lost Some strategies to mitigate the impact agriculture on soil erosion
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geog 5_notes1 - Agro-Ecosystems vs. Natural Ecosystems 1....

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