Agriculture notes

1. Agriculture notes

2. Brief History • Fossil evidence indicates that modern humans evolved in East Africa about 200,000 years ago • During most of there existence they survived by hunting and gathering • Agriculture started about 10,000 years ago • The development of agriculture gave rise to civilization. • http://www.history.com/shows/mankind-the-story-of-all-of-us/videos/mankind-the-story-of-all-of-us-farming

3. Subsistence Farming • Early agriculture was mostly subsistence farming • Subsistence farming – when the family produces just enough food to support the family unit (without excess intended for sale or trade) • Although this early farming method could deplete soil, it did not involved many of the environmentally detrimental techniques that are characteristic of modern farming.

4. Manipulating the environment • Agriculture by its very nature requires humans to manipulate the natural environment • Examples -plowing, tilling land -fertilizers -pesticides -monocultures -artificial selection -genetically modified organisms

5. Pests • Pest – a troublesome, destructive, or annoying organism (this definition is from a human’s perspective of course) • Pests can cause many problems -can compete with humans for food (destroy crops) -can carry disease (example – malaria and yellow fever) -can have negative effects on native wildlife/environment -can cause damage to residential and commercial property

6. Pests - examples • Insects (can be killed by insecticides) • Fungi (can be killed by fungicides) • Mammals (can be killed by rodenticides and other poisons) • Nematodes (can be killed by nematicides) • Birds (can be killed by avicides) • Weeds (can be killed by herbicides) • Any organism that “interferes” with human activities can be considered a pest

7. Pests – a man-made problem • Introduced species – often become pests • Monocultures (growing a single kind of plant over a large area) encourages pest development -provide abundant food supply -often eliminate/reduce natural predators • Pesticides – often make the pest problem worst by making the targeted pest stronger and destroying natural predators

8. The evolution of pesticides • Early pesticides – natural minerals or chemicals, were expensive and had limited success at controlling pests • Chlorinated hydrocarbons (including DDT) -discovered during WWI when insects were used to test chemicals (nerve gas) -became the most important group of insecticides

9. Chlorinated hydrocarbons • Cheap and easy to use • Killed many different kinds of insects • Continued to kill insects long after they were applied (persistent) • DDT was the first widely used chlorinated hydrocarbon • DDT was banned in the U.S. in 1972 due to its adverse effects on the environment http://www.cbsnews.com/news/the-legacy-of-silent-spring/

10. Pesticides -types • Persistent vs biodegradable – persistent take a long time to break down in the environment while biodegradable pesticides break down more easily • Broad-spectrum vs. selective – broad-spectrum kill many different organisms including the target pest while selective kill the target organism *In North America only 1 out 8 insects is considered a pest!

11. Pesticides Pros and Cons • Pro – saved millions of lives and billions of dollars worth of crops, protect humans from disease and hunger • Con – can affect the natural ecosystem (often times in ways that we can not predict), can cause health problems, often make pests stronger (resistant)