AGRICULTURE NOTES

Brief History Fossil evidence indicates that modern

humans evolved in East Africa about 200,000 years ago

During most of their existence they survived by hunting and gathering

*Picture taken from http://www.jantoo.com/cartoons/keywords/scavange

Brief History

Agriculture started about 12,000 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

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.

Subsistence Farming *Picture taken from http://

cnx.org/contents/7ccdfd4e-aa8a-4beb-b05a-9fa2be510152@1/Commercial_and_subsistence_far

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

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

Pests Picture of a female mosquito feeding*Picture taken from http://cal.vet.upenn.edu/projects/merial/introduction/intro_2.htm

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

Pests *Picture taken from http://npic.orst.edu/pest/learnpest.html

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

The evolution of pesticides

Early pesticides – natural minerals or chemicals, were expensive and had limited success at controlling pests

*Picture taken from http://www.awesomelyluvvie.com/2013/03/greyhound-roach-ride.html

Chlorinated Hydrocarbons -chlorinated hydrocarbons are a family a pesticides which include the pesticide DDT-discovered during WWI when insects were used to test chemicals (nerve gas) -became the most important group of insecticides*Picture taken from http://www.123rf.com/stock-photo/cockroach.html

Chlorinated hydrocarbons Cheap and easy to use Killed many different kinds of insects Continued to kill insects long after they

were applied (persistent)*Picture taken fromhttp://www.123rf.com/stock-photo/cockroach.html

Chlorinated Hydrocarbons 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/

Bald eagle populations decreased as a result of DDT use. * Picture taken from www.fws.gov

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!

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)