Chapter 12 – Agricultural land, water and yields

I. Food supply A. Total output = output/acre * acres 1. Focus is on cereal crop production since 50% of calories worldwide come from rice, wheat, maize (corn), sorghum, millet, etc. (16% comes from meat products)

2. Output per acre = yield 3. Between increase in crop production: a. 69% from improved yields b. 31% from additional land brought into cultivation

II. Available land in Developing Countries A. Can we increase output by increasing land in production? 1. Currently 760 million hectares (1.9 billion acres) in use

billion hectares of “rainfed land with crop potential” in developing countries (not counting China) a. 67% of this land is hilly, has poor soil, or has drainage problems  Cultivation may not be sustainable on these marginal lands

3. Potential to increase ag land varies by region a. Little potential for expansion in South Asia, Near East, North Africa b. Some potential for expansion in Brazil and Africa (Republic of the Congo and surrounding countries)

4. Land can be lost to ag production a. Farmland paved over by urban expansion b. Global warming may expand oceans and flood coastal areas or cause increased desertification

c. Ag land is degraded by soil erosion or contamination  nearly 1/3 of the world’s cropland has been abandoned over the last 40 years due to erosion

B. Can production be increased without increasing yields or acres? 1. Increase in double or triple cropping (getting 2 or 3 crops off of the same land in one year) 2. Increase in non-land-based food production (aquaculture, hydroponics)

III. Water A. Agriculture uses large amounts of water

1. Amount of irrigated land has grown steadily over time a. 10.3% of arable land irrigated in 1961 b. 17.8% of arable land irrigated in 2001

2. Irrigation is important for growing rice 3. Irrigated land provides 40% of total food worldwide 4. Yields on irrigated land are % higher than on non-irrigated land

B. Can irrigated land be increased? 1. FAO expects 1/2-2/3 of future increases in crop production to come from irrigated land 2. World Bank/UNDP estimate an additional 110 million hectares could be brought under irrigation

3. One study says ag cannot increase water use without causing substantial environmental problems a. UN overestimates potential  20% of the water is too remote  75% of the water occurs during floods

b. Water shortages are already showing up as groundwater depletion  Water tables are dropping

C. Water will have to be used more efficiently 1. Water harvesting (collecting runoff and using it when needed) 2. Drip irrigation (water delivered in small amounts to the roots of plants)

3. Crop varieties that need less water 4. Chemicals and/or more organic matter that hold water in the soil