Where our food comes from… Croplands (77%) Rangelands, pastures & feedlots (29%) Aquaculture (7%) There are 50,000 plant species that we can eat, yet 14 supply 90% of the worlds calories!!!
Food Sustainability 14 varieties of plants 2/3 of the world survives primarily on corn, wheat & rice alone Small number of species provide for meat & fish This all leads to food specialization Disease Environmental degradation Climate change
Industrialized Agriculture Heavy machinery Goal is to produce more food per area of land Characteristics include high fertilizer use, pesticide use, irrigation, genetic engineering, factory-like conditions Monocultures High resource use
Case Study: Industrialized Food Production in the United States Industrialized agriculture uses about 17% of all commercial energy in the U.S. and food travels an average 2,400 kilometers from farm to plate. Figure 13-7
Traditional Agriculture Labor- intensive Polyculture Usually lower resource use Can have a higher output than Industrialized Less susceptibility to changes
Traditional Agriculture: Low Input Polyculture Many farmers in developing countries use low-input agriculture to grow a variety of crops on each plot of land (interplanting) through: Polyvarietal cultivation: planting several genetic varieties. Intercropping: two or more different crops grown at the same time in a plot. Agroforestry: crops and trees are grown together. Polyculture: different plants are planted together.
SUSTAINABLE AGRICULTURE THROUGH SOIL CONSERVATION Modern farm machinery can plant crops without disturbing soil (no-till and minimum tillage. Conservation-tillage farming: Increases crop yield. Raises soil carbon content. Lowers water use. Lowers pesticides. Uses less tractor fuel.
Contour Farming –sloping your growing crops, etc. You run terraces parallel to the ground to stop soil from running down a steep slope. Plowing and planting crops in rows across, rather than up and down, the sloped contour of the land.
Terracing – (what you use for contour farming.) Dirt goes up to hold the dirt in place. Broad, nearly level terraces that run across the land contour. Helps to retain water for crops at each level and reduce soil erosion by controlling runoff.
SUSTAINABLE AGRICULTURE THROUGH SOIL CONSERVATION Terracing, contour planting, strip cropping, alley cropping, and windbreaks can reduce soil erosion. Figure 13-16
Strip Cropping – a row crop such as corn alternates in strips with another crop that completely covers the soil, reducing erosion. It catches and reduces water runoff and helps prevent the spread of pests and plant diseases.
Cover Cropping (alley cropping) – several crops are planted together in strips or alleys between trees and shrubs that can provide shade (which reduces water loss by evaporation) and helps to retain and slowly release soil moisture.
Irrigation Techniques Conventional center-pivot irrigation- allows 80% of the water input to reach crops Gravity-flow irrigation- Valves that send water down irrigation ditches. Drip irrigation- Can raise water efficiency to 90-95% and reduce water use by 37-70%. Floodplain irrigation- allowing the natural floods to irrigate the crops. Soils in flood zones tend to be nutrient rich and fertile.
The Green Revolution Increased food production using industrialized crop production (heavy machinery) Steps of the Green Revolution 1. Plant monocultures of high yield crops (wheat, corn, rice). Often genetically modified. 2. Use high amounts of fertilizers and pesticides to increase yield 3. Increase the number of crops grown per year
Meat consumption on the rise Effects: More densely packed feedlots High use of grain and or fish meal Increased need of grain can lead to dependance on other countries
Fig. 13-21, p. 289 Trade-Offs Animal Feedlots AdvantagesDisadvantages Increased meat production Need large inputs of grain, fish meal, water, and fossil fuels Higher profits Concentrate animal wastes that can pollute water Less land use Reduced overgrazing Reduced soil erosion Antibiotics can increase genetic resistance to microbes in humans Help protect biodiversity
PRODUCING MORE MEAT Efficiency of converting grain into animal protein. Figure 13-22
Harmful Environmental Impacts of Agriculture Erosion Degradation of soil Water depletion Water pollution Greenhouse gasses Air pollution Biodiversity loss **according to the EPA, agriculture is responsible for 75% of water quality issues in US rivers & streams
Higher use of Biofuel Biofuel is a renewable energy alternative However, using too much biofuel aggravates the problems brought on by agriculture. Are we replacing one problem with another?
Aquaculture Raising fish in ponds and underwater cages (43%) Helps with over-fishing Decrease contamination (ex. Mercury)
Fig. 13-24, p. 292 Trade-Offs Aquaculture AdvantagesDisadvantages High efficiencyNeeds large inputs of land, feed, and water High yield in small volume of water Large waste output Destroys mangrove forests and estuaries Can reduce overharvesting of conventional fisheries Uses grain to feed some species Low fuel use Dense populations vulnerable to disease Tanks too contaminated to use after about 5 years High profits Profits not tied to price of oil
Purse Seines A large purse-like net is put into the ocean and is then closed like a drawstring purse to trap the fish. Tuna is a fish typically caught in purse seines Dolphins are a by-catch of purse seines
Long-line fishing Lines are put out that can be up to 80 miles long w/ thousands of baited hooks on them. These are left out free- floating for days and then the boat comes back and picks them up. Pilot whales, dolphins, sea turtles, and birds are by-catch of this technique.
Drift-net fishing Each net hangs as much as 50 feet below the surface and up to 34 miles long. Anything that comes into contact w/ these nearly invisible nets are entangled. This leads to overfishing Many unwanted fish and marine mammals, turtles and seabirds are caught.