Agricultural Land and Water
Text extracted from
The World Food Problem
Leathers & Foster, 2004
ttp://www.amazon.com/World-Food-ProblemToward-Undernutrition/dp/1588266389
Agricultural Land Use
Source: NASA
http://lcluc.umd.edu/images/Science_Themes/Foley1-large.jpg
Land Availability
• Ag land has increased
slowly
–
–
–
–
2.8% 1960s
2.3% 1970s
3.7% 1980s
2.1% 1990s
• Most increases in
pasture land
Grazing cattle, Brazil
http://www.ypte.org.uk/docs/factsheets/env_facts/env_images/brazil_cattle.jpg
Land with Crop Potential
• 2.57 billion hectares of
land with crop potential
– Excluding china
• Only using < 1 billion
• Problems with most
unused potential land
– Hilly
– Poor soil
– Poor drainage
• Could increase ag land
– 30%
China
http://www.agapetea.com/store/images/common/about_blacktea3.jpg
Potential arable land
Agricultural Intensity
HANPP: Human Appropriation of Net Primary Production
http://www.eoearth.org/upload/thumb/4/45/HANPP_Figure_3.jpg/625px-HANPP_Figure_3.jpg
Land lost to Ag production
• Urban expansion
– Small effect worldwide
• Global warming may
flood coastal areas
• Soil degradation
– 1/3 cropland
worldwide abandoned
due to erosion
http://upload.wikimedia.org/wikipedia/commons/thumb/7/7b/Erosion.jpg/397px-Erosion.jpg
Irrigation
• World Water Use:
– Agriculture
– Domestic
– Industry
69%
8%
23%
• Irrigated crops provide
40% of food worldwide
• Yields with irrigation
increase 2-3X
Irrigated land
http://upload.wikimedia.org/wikipedia/commons/4/4a/Irrigated_land_world_map.png
Water withdrawals for irrigation
http://news.bbc.co.uk/nol/shared/spl/hi/pop_ups/04/sci_nat_feeding_the_world/img/3.jpg
Sandra Postel
• “Water use tripled
between 1950 and 1990
– as world population soared
by some 2.7 billion…
• Worldwide demand for
water cannot triple again
– without causing severe
shortages for
• crop irrigation,
• industrial use,
• basic household needs
http://www.hipco-ne.com/images/gated.gif
http://www.globalwaterpolicy.org/images/sandrapostel1_19.jpg
and
• critical life-supporting
ecosystems”
Conserving Ag water
• Water harvesting
– Collecting and
saving runoff
• Drip irrigation
• Drought tolerant
varieties
Drip irrigation
http://static.howstuffworks.com/gif/irrigation-drip.jpg
Colorado River
• River is drained dry
– before it reaches the ocean
• Heavy irrigation use
–
–
–
–
Colorado
Arizona
California
Mexico
• City water supply
California irrigation from the
Colorado River
http://aquafornia.com/wordpress/wp-content/uploads/2008/02/irrigation-_2-by-bor-pfs.jpg
– Las Vegas
– Phoenix
– Tucson
Irrigation in China
• Yellow river used for
irrigation
• River ran dry in 1972
– For 15 days
• Since 1986 runs dry
Yellow River
every year
• In 1997, dry for 227
days
India River Interlink Plan
• $200 billion plan
– to bring water to south India
• Will link 36 rivers with
canals
– Completed in 2016
• Potential benefits
– Reduce flooding
– Hydroelectric power
– Irrigation
http://www.ben-center.org/riverMaps/RiverLinkingMainMap.jpg
Vandana Shiva
• Industrial ag requires 5x
water of indigenous ag
– wheat and rice
• Pumping groundwater
not the solution
– Aquifers depleted
• Big dams not the
solution
Small dam, India
http://farm4.static.flickr.com/3018/2397775485_c4fce43d8d_m.jpg
http://www.netradiomeeting.it/public/foto/SHIVA_VANDANA.jpg
–
–
–
–
benefit cities, investors
Ecologically destructive
Displaces poor farmers
Many small dams better
Aswan Dam, Egypt
• Benefits
– Controls flooding of
Nile River
– Hydroelectric power
• Problems
– Fertile silt not
deposited
• Farmers must use
fertilizer
http://www.2travel2egypt.com/sightseeing/images/aswandam.jpg
– Schistosomiasis
increase
– Nile delta receding
– Increased salinity