Human Food Supply We wish to know: is the world food supply keeping pace with population growth? What are the means of increasing the world food supply?

Human Food SupplyHuman Food Supply

We wish to know:

• is the world food supply keeping pace with population growth?

• What are the means of increasing the world food supply?

• What are the limits to how much we can increase the world’s food supply?

Population and Food - A Historical View

• Malthus, 1798, predicted that population growth would outrun food supply

• doom-sayers of 1960s echoed Malthus’ prediction• world grain output expanded by a factor of 2.6

from the 1950s to the 1980s• except for parts of Africa, food production

exceeded population growth throughout the world

World:• Total area: 510.072 million sq km • Land area: 148.94 million sq km • Water area: 361.132 million sq km • Comparative area: land area 16 X US

Land use:• Arable land: 10% • Permanent crops: 1% • Meadows and pastures: 24% • Forest and woodland: 31% • Other: 34% (surface not covered with plants, e.G.

Antartica, deserts, mine sites, urban areas).

Need slides on Green rev. and

NPP

Need slides on Green rev. and

NPP

Can We Increase the Amount of Arable Land?

• Arable land is approx 10% of total land area• most land is too wet, dry, steep, or cold• most arable land is already under

production (eg, 80% in Asia)• much land that is highly productive under

native vegetation (eg, rain forests) is not useful to us, and not productive if farmed

• does not appear to be a promising solution

Can We Increase the Yield per Unit of Land?

• Green Revolution is spectacular evidence of success with cereal crops, especialy rice

• selective plant breeding produced high yielding varieties (HYVs)

• yields of rice, sorghum, maize rose dramatically, and even increased substantially on a per capita basis

World NPP and Human Consumption

• World NPP is approx 224.5 Pg/yr

• 1 pentagram = 1015 g = 109 metric tonnes (1 metric tonne = 1,000 kg)

• Terrestrial NPP > Aquatic NPP (despite oceans being 70% of area)

World Net Primary Production

Area (left) and total (right) NPP. From http://www.sprl.umich.edu/ GCL/Notes-1998-Fall/energyflow.htm

Climate and NPP

NPP is strongly dependent upon climate. From http://www.sprl. umich.edu/GCL/Notes-1998-Fall/energyflow.htm

The Need to Explore New Crop Species

• 90% of world’s food comes from just 15 plant and 9 animal species

• cereal grains-- wheat, rice, maize, millet and sorghum -- provide more than 2/3rds of the world’s production of edible dry matter and half of the world’s protein.

Biotech Crops: Risk and Promise

• Frankenfoods, or a boon for the world? • Vitamin A-producing rice could benefit

malnourished millions• drought, disease and pest-resistant crops

could provide the next green revolution• but genes could “jump” from trangenic plants

to wild plants, creating monster weeds• today, a large fraction of our corn and soybeans are

“roundup-resistant”, allowing wide use of herbicide (and no-till agriculture which protects waterways)

• Much bigger issue in Europe than in USA

Bt Corn Pollen kills Monarch Butterflies

Transgenic corn containing Bt genes is resistant to ravenous larvae of the European corn borer and corn earworm. But a heavy dusting of its pollen on milkweed kills larvae of the Monarch.From: Transgenic Corn vs. Monarch Butterflies, Barry A. Palevitz, June 7, 1999 <<http://www.thescientist.library.upenn.edu/yr1999/june/palevitz_p1_990607.html>>

Biotech Foods - Dilemma for Producers• Genetically-modified crops are now widely grown

– 52% of soybeans (38 m of 73 million acres)– 25% of corn (19 m of 76 m acres)

• Foodstream can not easily separate g.m. from non-g.m. crops

• American Medical Association: – g.m foods are "substantially equivalent to their

conventional counterparts" – no long-term side effects have yet been detected

• Major food producers are unsure of public’s response to genetically altered crops– McDonald’s has asked suppliers not to ship genetically-

modified potatoes, but cooks fries in vegetable oil made from g.m. corn and soybeans (NewYork Times 4 June 2000)

Biotech Crops: Biotech Crops: Some WebsitesSome Websites

• www.nbiap.vt.edu

• http://usinfo.state.gov/topical/global/biotech/

• www.nal.usda.gov/bic/

Summary

• long-held expectation that pop. will outrun food supply • from 1950s to 90s, per capita food production increased.• The Green Revolution produced enormous increases in

yield per hectare. However, environmental costs are high.• Most arable land already is farmed, and the land area

under agriculture has slightly declined.• Improved agricultural methods that increase yields while

minimizing environmental impacts hold the greatest promise

• humans now use or co-opt a substantial fraction of the world’s terrestrial net primary production