In the end, how does all of this matter?

Some issues arising from the study of crop evolution:

Will agriculture continue to feed and cloth the world?

© Paul Gepts 1997-2010


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Sources

  • Required:
    • Godfray HCJ, Beddington JR, Crute IR, Haddad L, Lawrence D, Muir JF, Pretty J, Robinson S, Thomas SM, Toulmin C (2010) Food Security: The Challenge of Feeding 9 Billion People. Science 327:812-818
      Available from course web site or PLB143-S10 Smartsite
    • Kiers ET, Leakey RRB, Izac A-M, Heinemann JA, Rosenthal E, Nathan D, Jiggins J (2008) ECOLOGY: Agriculture at a Crossroads. Science 320:320-321 Available from course web site or PLB143-S10 Smartsite
  • Others:
    • Cohen JE (1995) How many people can the earth support? Norton, New York.
    • Bongaarts J (1994) Can the growing human population feed itself? Sci. Amer. March 1994: pp. 36-42
    • Postel S (1994) Carrying capacity: Earth's bottom line. In: State of the World 1994. Norton, New York: pp. 3-21
    • Brown LR (1994) Facing food insecurity. In: State of the World 1994. Norton, New York: pp. 177-197
    • Brown LR, Kane H (1994) Full house. Norton, New York.
    • Eberstadt N (1995) Population, food, and income. In: Bailey R (ed.) The true state of the planet. Free Press, New York: pp. 7-47
    • Haub C (1995) Global and U.S. national population trends. Consequences 1 (2): http://www.gcrio.org/CONSEQUENCES/summer95/population.html
    • Rosenzweig C, Hillel D (1995) Potential Impacts of Climate Change on Agriculture and Food Supply. Consequences 1 (2): http://www.gcrio.org/CONSEQUENCES/ summer95/agriculture.html
    • Xiao J, Grandillo S, Ahn SN, McCouch SR, Tanksley SD, Li J, Yuan L (1996) Genes from wild rice improve yield. Nature 384: 223-224
    • Plant and Population: National Academy of Sciences Colloquium, Dec. 5-9, 1998, Irvine, CA:
    • Fedoroff NV, Cohen JE. 1999. Plant and population: is there time? Proc. Nat Acad. Sci. USA 96: 5903-5907 and additional papers in the series
    • Morris M, Hill A. 2006. Ethanol opportunities and questions. http://attra.ncat.org/attra-pub/ethanol.html
  • Presentation slides:

Issues (among others...)

How many people can agriculture (in the broadest sense) support?
    • Hunters-gatherers: most involved in food procurement --> developed societies: 2% involved in food production
    • Unprecedented growth in world population
    • Increases in food production. How much more and for how long?
  • Where do we find genetic resources and who owns them?
    • Increases in food production based in part on genetic improvement
    • Genetic resources is the raw material of plant (or animal) breeding
    • Most genetic resources are found in LDCs; most breeding efforts take place in DCs

Phases in human population growth (from Cohen 1995)

Phase Average date Population ( x 10^9) Doubling time before  Doubling time after
Local agricultural 8,000 BC 0.005 40,000-300,000 1,400-3,000
Global agricultural 1,750 AD 0.75 750-1,800 100-130
Public health 1,950 AD 2.5 87 36
Fertility 1,970 AD 3.7 34 (peak) >40 (since 1990)

At the peak, there was a global population growth rate of 2.1% per year. Currently, this growth rate has dropped to 1.4% per year.

Number of years required to add one billion people to the population of the earth

(from Haub 1995)


Date achieved Years required
First billion 1800 All of human history
Second 1930 130
Third 1960 30
Fourth 1974 14
Fifth 1987 13
Sixth 1998 11
Seventh 2009 11
Eighth 2021 12
Ninth 2035 14
Tenth 2054 19
Eleventh 2093 39

Demographic transition

(Cohen 1995)

  • Pattern of changes in birth, death, and population growth rates
  • Four phases:
    • High birth rate, high death rate: --> low population growth rate
    • High birth rate, lower death rate: --> higher population growth rate (mortality transition)
    • Lower birth rate, low death rate: --> population growth slows (fertility transition)
    • Low birth rate, low death rate: --> low population growth rate, but large population
  • All countries have undergone this transition (developed countries) or are undergoing it (developing countries)
  • Lower death rates:
    • Largely due to improvements in sanitation, diet; reductions of enviromental hazards; behavior
    • To a limited extent, improvements in medical care

Contrasting demographic transitions

(from Haub 1995)

  • Developed country: Sweden 
  • Developing country: Mexico 

Differential population increase between DCs and LDCs

(from Haub 1995)

  Currently, 1.2  billion people live in developed countries, whereas 4.8 billion people live in developing countries. This ratio of one in 5 may reach 1 in 10 in 2050.

Prediction of future population increases

  • TFR: Total fertility rate = average number of children per woman
  • Some values for TFR:
    • replacement TFR? 2.06
    • current average TFR in LDCs:
      • including China: 3.6 children
      • without China: 4.2
    • in the 1950s: 6.1
  • Difficult to predict future values of TFR:
    • e.g., U.N. 1951 prediction for world population in 1980: predicted: 3.0-3.6 x  109; actual: 4.4 x 10 9

TFRs and L(0)s in selected LDCs


1950-55 1970-75 1990-95

TFR E(0) TFR E(0) TFR E(0)
Kenya 7.5 41 8.1 51 6.3 56
Mali 7.1 33 7.1 39 7.1 46
India 6.0 39 5.4 50 3.4 60
Philippines 7.3 48 5.5 58 3.9 66
Mexico 6.8 51 6.4 63 3.2 71
Brazil 6.2 51 4.7 60 2.9 66

TFR: total fertility ratio;  L(0): life expectancy at birth

Factors affecting TFR change

(Cohen 1995)

No consistent factors explaining changes in fertility except " P arents must be ready, willing, and able to control their fertility. "
  • Acceptable mode of thought and form of behavior
  • Reduced fertility must be advantageous: e.g., children become a liability, for ex., by requiring schooling
  • Techniques of fertility reduction must be available

Organized efforts to lower fertility

  • Examples: Governments of China vs. India: 1 child per couple vs. 2 children per couple (green: below carrying capacity; blue: below current national average TFR of 3.6; red above TFR of 3.6)
  • Policies to reduce fertility:
    • promote family planning & contraceptives 
    • develop economies
    • protect children
    • educate and employ women
    • educate men (about fertility)

Predictions of U.N. on future world population levels

  • Pessimistic scenario: current growth at 1.4% per year continues without reduction of the yearly growth rate; this leads to a doubling of the world population to 12 billion in 50 years.
  • Optimistic scenario: annual increase of 80 million per year drops to 0 over 50 years; this leads to a population increase of 2 billion to 8 billion over 50 years.




  • Carrying capacity

    Some concepts
    • How many people can the earth support?
    • = "Largest number of any given species that a habitat can support indefinitely."
    • Indefinitely: without damaging the resource basis
    • Major difference with animals: not local, but (increasingly) worldwide (trade, transportation)
    Examples
    • Vancouver (Canada): I
      • Individual needs:
        • 1.1 ha food
        • 0.5 forest products
        • 3.5 ha biomass (fuel)
      • For 1.7 million people: 8.7 million ha land vs. 400,000 ha in Vancouver and surroundings (x22)
    • Netherlands: Requires x14 productive lands
    Net primary productivity (NPP)
    • "The rate at which energy is bound or organic matter is created by photosynthesis, per unit of the earth's surface per unit time."
    • Humans appropriate 40% of NPP on earth.



    Food production trends

    (from FAO Yearbook by Avery 1995)


    Total food production Total food production/capita

    1978 1984 1990 1978 1984 1990
    All LDCs 99 116 141 99 105 114
    Africa 103 106 132 103 94 98
    Latin America 100 109 127 100 100 103
    Asia 99 119 145 99 110 120

    What can be done to increase food production?

    Increase land under cultivation

    • Only 11% of farmable land now used

    • Additional areas: mainly grasslands in Africa and Latin America
    • Increase frequency of cropping
    But:
    • Slowdown in harvested grain area in 1990s

    • Reduction in world grain land per person


    • Potential additional land available for agriculture






    Increase potential yield of crops

    • No reduction in yield increases apparent
    • Xiao et al. (1997)
      • Two genes from a wild rice species, Oryza rufipogon
      • Increase yield by 18 and 17%, respectively
      • Unexpected: because O. rufipogon yields only half of cultivated rice

    (from D. Mackill, formerly at USDA-ARS Rice Genetics Program at UC-Davis )




    Close gap between potential and actual yields

        • may require too much fertilizers, irrigation, etc
        • breeding for tolerance to low soil fertility, drought, etc.




    Reduce storage and distribution losses


    Alternative crops:

    e.g., kenaf (Hibiscus cannabinus)

    • Same family as cotton and okra
    • Originated in Africa
    • Used traditionally for rope, twine, sack (from stem phloem)
    • Proposed for paper pulp: bond paper to newsprint (from stem core)
    • Produces 3-5 more tons of fiber per acre per year that the southern white pine. Uses 15-25% less energy to pulp than southern white pine.




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