Paul E Waggoner
Thank you for inviting me to deliver the second Kuehnast lecture in 1994 and attend Don Baker’s graduation.
I garden because I like to dig. Farmers farm to feed over 5 billion people now, and ahead in an uncertain climate‑‑feed ten billion. The world's farmers and I share this: We want to do something. So I shall push beyond Malthusian gloom to hope. I shall push on to doing something about feeding multitudes, coping with climate change and sparing Nature.
Near the time
Ten times the 1 billion that made Malthus gloomy triggers the cry, "Mobs will crowd out Nature".
in the Old Testament condemned sinners to wilderness, and medieval folk feared
bandits and trolls lurking in wilderness.
But before the French revolution, Rousseau wrote of the nobility of
unspoiled children and Nature. In the
era of Lewis,
Gloom caused a speaker at the AAAS meeting last winter to advocate a world population of 2 billion, requiring 3 billion of today's 5 billion depart.
In a gentler mode, legislatures proclaim and patrons
purchase nature or wilderness reserves.
But proclamations from
Representing the American states in
I asked myself what could be the reason that so many should be permitted to beg who are willing to work in a country where there is a very considerable proportion of uncultivated lands? These lands are kept idle mostly for the sake of game. ...
Whenever there is in any country, uncultivated lands and unemployed poor, it is clear that the laws of property have been so far extended as to violate natural right. The earth is given as a common stock for man to labour and live on. If we [allow land to be appropriated], we must take care that other employment be furnished to those excluded ... If we do not, the fundamental right to labour the earth returns to the unemployed. ...
The French soon restored the fundamental right with the guillotine. Reserves persist only when land can be spared.
Spared causes me to
write what I call
A = P * F *
The residuum after A is cropped will be spared for other uses, including Nature.
10% fewer people, 10% fewer calories per capita or 10% more yield per hectare (ha) spares 10% cropland. Changing one factor is as good as another is.
How much cropland?
In 1990, roughly 30% of the world's land was forest, 30%
grass, and 30% the miscellany called Other.
Crops grew on 10%. Crops cover
about twice the area of the 48
Wilderness accounts for the 27% without such development as crops, settlements or roads. The World Resources Institute (WRI) estimates that Wilderness, which overlaps the classes of the pie, occupies between two and three times as much land as crops.
For three centuries cropland advanced and forest retreated. Multiplication of people between 1980 and 1990 lowered the Food and Agricultural Organization (FAO) estimate of cropland per person to 0.27. Pessimists call less cropland per person, narrowing the resource base; optimists call it high yields sparing land.
In fact, FAO reports calories per capita rising about 0.4% per year in rich countries. In poor countries, they report twice as high percentage rise in calories per capita.
improved the food supply despite less cropland per capita? World farmers raised yields even faster than
people multiplied, simultaneously sparing land and improving food supply per
capita. A happy demonstration of
Ten times the population that frightened Malthus, twice
today's population living in an uncertain climate, however, makes the middle of
the 21st Century a new game. Given 90% of global land stands uncultivated, people
will expand cultivation if they are unemployed and poor.
stands near 1.5 billion ha now, yielding an average slightly less than 2 tons
or 8 million calories per ha in food, feed and fiber. In tons/ha yields range
from 1 for arid African wheat to 8 for Irish wheat and
Although 3,000 on the plate sustain people, the curve pertains to all crop production, and we use crops for many things besides food. For example, we feed some to animals, sip some as coffee and wear some as cotton. Because today's cropland grows about 6,000 original cal/day for today's population, diet and uses, I concentrate on the lower, red curve of 6,000 cal/day for tomorrow's ten billion.
Will changing climate lower yield and expand cultivation? I remember my promise to push on to doing something (Yes, doing something) about feeding multitudes, coping with climate change and sparing Nature.
A panel of CAST (The Council on Agricultural Science and Technology) kept the spotlight on doing something by asking this Big Question:
For a warmer planet with more people, more trade,
and more CO2 in the air, can
The first phrase begins with the warming of climate change. It implies rearranged precipitation. It emphasizes the simultaneous changes of more people and more trade. NAFTA, GATT and technology will accelerate trade. "More CO2 in the air" reminds that the greenhouse gas CO2 is the stuff of photosynthesis and crop yields.
The second phrase, "Can U. S. farming and forestry prepare within a few decades" sets a deadline for adaptation matching the period visualized for climate change.
"Sustain more production" quits scenarios of farmers and scientists dumbly suffering. By the time climate changes, the production of today will be irrelevant. To maintain and improve the human condition, the farmers of 2050 AD must more than double the present crop. And they must keep it up.
The final phrase is "While emitting less and stashing
away more greenhouse gases". Farming does emit the greenhouse gases CO2,
methane and nitrous oxide. Burning
fossil fuels dwarfs the climate forcing by
The Big Question asked by CAST brings home that the search for adaptations will be harder and cope with more than climate. The search will never end. But hardships are reasons for prompt action‑‑not transfixed dismay.
Returning to the first phrase, I ask whether warmth, water or CO2 will be the preeminent factor affecting crops in a new climate in the mid 21st Century.
I begin with CO2. Optimists see a stimulation of photosynthesis from more CO2, and pessimists see little benefit or even harm. Their disagreement commands newspaper headlines.
That more CO2 in the air enhances growth has been known for nearly two centuries, and growers enrich CO2 in greenhouse air about three fold to speed growth.
But will more CO2 outdoors help ten billion spare
more land for Nature? For a few weeks
after the CO2 around Alaskan tundra was raised, photosynthesis sped
up but subsequently slowed to that in normal CO2. In contrast, the
speeding of photosynthesis by extra CO2 in a
A major force in resolving how CO2 affects crops
is Idso, protege of Don Baker. When Idso
doubled CO2 around orange trees in
While research sorts out the effects of CO2 on a
global scale, the best refuge continues to be the speeding of photosynthesis by
CO2 as shown by
Carbon dioxide in the air likely will continue rising 1 to 2 ppm per year or one third while population grows to ten billion. Measurements of photosynthesis suggest that this will increase photosynthesis and perhaps crop growth some 10% in crops such as wheat and 5% in those such as maize. Although rising CO2 may not materially augment, it will certainly not limit food production for ten billion people nor lessen the land that they can spare for Nature.
What will warming cause? Bjorkman observed two C4 plants, one adapted to cool and one to warm temperatures. A few degrees warming harms these species little. In fact, warming helps the photosynthesis of the adapted species up to 45 C or 113 F.
Physiologists worry that warming will lower yields by speeding crops through their cycles. Certainly warming speeds up mathematical models that employ degree‑days. Although questions will continue whether faster passage through life will prevent exploiting the advantage of longer warm seasons, warming affects photosynthesis little and effects of warming pale beside the greater effects of water.
Frank and colleagues dried and re-wet wheat during the heading of winter wheat. As the water potential fell below the wilting percentage at -15 bars, photosynthesis promptly fell to a quarter. Watering above the wilting percentage recovered photosynthesis, eventually to about 3/4 of the initial rate.
One can call the jump in photosynthesis through the threshold of the wilting percentage a non-linearity. Put one way, if climate change passes through a non-linearity, it will affect matters profoundly. Put another way, discovering non-linearities far exceeds the importance of precise quantitative observation between non-linearities.
So while global warming grabs headline, the active ingredient of any climate change will be water supply, locally.
Because the active ingredient of climate change is water, scenarios of water supply in real fields are essential. The water that controls photosynthesis is not a global average but instead that around the roots in a specific field. Although average global warming may be easier to project, only projections of local water supply matter.
Puzzled by a patient's complaints a doctor said, "Why don't you have fits. I can cure fits." Reckoning average global warming is as futile as asking the patient to have fits because the doctor can cure fits.
Three world class computers projected changes in summer
precipitation. For your
And so it goes for other seasons and locales.
Beyond the variation among computers, I offer two more demonstrations of uncertainty. In their 1983 appraisal the National Academy of Sciences (NAS) saw so little progress in computation that they simply repeated a 4-year-old appraisal: Doubling CO2 would warm the global average 2.5 to 3.5 C.
In 1992 the NAS again appraised computations. Instead of narrowing the range of uncertainty after nine years, they broadened it from 2.5 to 3.5 out to 1 to 5 C. This month an IPCC report says 1.5 to 4.5 C.
The second demonstration of uncertainty comes under the heading of crying wolf. During the severe drought of 1988, computers of global warming proclaimed before Congress and in the press that global warming had arrived. Five years later, in 1993, rain inundated you.
Before answering the Big Question of how agriculture should prepare for changing climate, the panel of CAST concluded that the heart of the issue was uncertainty. So when I come to action, I shall propose action, not for a neat and naive scenario of climate, but for climate that is uncertain.
A challenge in weighing impacts is compounding climate with
other changes. To grasp the changes that
next century might accompany climate change and 10 billion people, look back to
1919 when Earl Kuehnast appeared on an
A book from Iowa entitled “In No Time at All” shows horses pulled 1919 plows, farmers walked behind, and fuel for horses and mules occupied a quarter of cropland. The environmental issue was flies, and a quarantine sign nailed to the front door arrested scarlet fever’s spread. High tech meant a cow tester in a buggy, and a cream separator on the back porch. Yes, in no time at all.
The ice on
Changes since 1919 teach that we must go beyond computation of the effect of 1 to 5°C warming on today's corn. We must foresee farmers' adaptations to warming amidst a flood of technological, social and economic changes. If we ignore these adaptations, we shall write a "dumb farmer scenario". Imposing the climate near the middle of the next century on the activities of 1994 implies dumbly ignoring new circumstances for decades.
Simulating effects of future weather on present farming does provide a worst case scenario, the case of dumb farmers. The CAST report on climate change cited two climate change scenarios for doubled greenhouse gases along with more CO2 in the air. All climate scenarios specified in the underlying Environmental Protection Agency (EPA) study called for warming--but different precipitation. Compared to the present yields, the scenarios produced yields ranging from mild gains to severe losses. Again, the uncertainty of the impacts of climate change, even on imaginary farmers dumbly suffering.
Encouraged by report of the Panel on Policy Implications of
Greenhouse Warming (NAS) report naming adaptation among the options for global
warming, investigators have turned their minds to adaptation, to farmers like
the real, smart ones. The so-called MINK
study, MINK for
During 1951-80 unirrigated corn yielded near 8 tons/ha. The MINK investigators envision yields rising to about 13 tons by 2030 if climate doesn't change. A yield of 10 is their estimate of what the analog climate, the Dust Bowl, would do to unadapted farming growing corn in 300 ppm CO2. Adding the benefit of more CO2 produces 11. Finally, they envision CO2 plus the adaptations on the right would raise yields over 12, higher than now and about the same as 2030 without climate change.
Recently, Rozenzweig and Parry reported an ambitious, international estimate of the effect of a warming of 4 to 5 C, at the top end of IPCC's 1.5 to 4.5 C. They asked agronomists around the world to opine what adapted farming would suffer. Although the authors warned that poor countries would likely suffer, they estimated this severe warming would change global production little.
Nordhaus and others at Yale sought a measure of real rather
than conjectured adaptation. Arguing
that land prices reflect the best adaptation farmers can make, Nordhaus related
land prices rather than yields in U.S. counties to climate. For a
The generality is: For each uncertain scenario, someone can compute its impact on fictitious farmers who would dumbly suffer the change without adapting. And someone can speculate about a world of real, adaptable farmers.
I, however, promised to do something about feeding multitudes, sparing Nature and coping with climate change.
Answering their Big Question, the CAST panel found the crux of climate change is uncertainty. They proposed a prudent nation will hedge for the risks of uncertainty by assembling a diverse portfolio of ten agricultural assets and assure flexibility to use them. The assets:
Land, Water, Energy, Physical infrastructure, Genetic diversity, Research, Information systems, Human resources, Institutions, Market.
First I illustrate diversity and flexibility with the assets of land, trade and institutions. Then I turn to water--the active ingredient of climate change, and to research--your business.
In land, diversity brings diverse climates. Good weather and improving climate in one region can balance losses in another.
Trade exchanges the fruit of diverse climates. As the invisible hand that coordinates adaptation, the world market is a priceless climate change asset. Freeing trade imparts the essential flexibility.
Governments exemplify institutions. If their policies are harmonized, their subsidies of, say, declining crops or water will not hobble adaptation. Neither will their disaster relief discourage adaptation to a new climate or water supply.
Now, water. Water
already limits cropping in places, other demands are cutting into the water
left for irrigation, and irrigated area is shrinking in all
Ahmad found Pakistani farmers fertilize to raise the yield from three levels of irrigation. Lifting the yield from each level of irrigation fertilizer improved water use efficiency. Ahmad wrote, "Water cannot be considered to have become a real constraint to meeting the world food supplies as long as there is the scope for manipulation of the various underlying factors for further increasing the agricultural production".
use efficiency is the kg of crop grown per cubic meter of water evaporated. Observations assembled by Jensen’s showed the
gilt edge of research in employing the asset of water. From the 1960s into the 1980s,
evapotranspiration ET from
CAST wrote that on an inflexible globe, research is the gilt-edge investment that will be asked to do much of the work of adaptation. The right response to an uncertain future is technical change widening the possibilities of substitution among natural resources and between resources and technology.
Given this central importance of research and their responsibility for knowledge of the landscape and farming the agricultural experiment stations in 1994 published “A guide for agricultural experiment stations to the questions and research anticipating global climate change”. The guide focuses on weather, its relations to crops and exchanges of energy, water and gas between crops and atmosphere. It puts central questions about climate change that Stations have a comparative advantage for answering.
I report five of the questions, beginning with a micrometeorological one.
How much does cutting or planting forests change the energy budget and so the climate of a region?
Lists of activities affecting greenhouse gas condemn deforestation and urge reforestation. By and large, however, they overlook the full effect of vegetation on the energy budget of the earth.
Tall forests lessen the reflection of solar radiation. Gash and colleagues computed that less reflection raises by a quarter the energy for evaporation and heating. Other scientists computed that cutting boreal forests and exposing more reflective snow overwhelmed the expected warming from the carbon released from the forest. Tall, dark trees evaporating water drawn by deep roots may affect climate in more, surprising ways than foreseen by a single-minded focus on carbon in their trunks.
Agricultural meteorologists hold a comparative advantage for removing uncertainties about the energy budgets of forests versus short vegetation.
Although the label global warming focuses attention on temperature, the lever of climate change that harms or helps crops and forests will be water. So the question
How will changed climate and CO2 plus changed vegetation alter evapotranspiration?
An open question is whether more CO2, which is feared as a greenhouse gas, will narrow foliar pores enough to change evapotranspiration. In the long-run outdoors? Up, down or inconsequentially? Plant physiologists need professional help--from meteorologists.
Can the microclimatic models for the soil-plant-atmosphere continuum of plots be put together to simulate regions in general circulation models (GCMs)?
The tools for anticipating climate change by calculation, GCMs, must simulate processes from the small scale of evaporation from fields to the great ocean currents. Having invested years in models of the soil-plant-air continuum, agricultural meteorologists should now realize a return by furnishing an underpinning for GCMs that is realistic enough to reflect the physics of the landscape but simple enough to put in GCMs.
The NAS Panel on Policy Implications of Greenhouse Warming wrote, “Monitor climate, forecast weather”. They hoped to relieve the obsession with forecasting the climate a century from now while neglecting to observe whether climate is changing. So the question:
Are climate, radiation and pollution changing in the countryside?
Agriculture employs many of the nation's environmental observatories in the countryside. The countryside is exactly where global changes must be detected. It is where crops and forests grow. So agriculture has an advantage--and responsibility--to assure the comparability and continuity of their observations of weather, radiation and pollution. Starting the St Paul Climatological observatory in 1960 and--even harder--keeping it going, Don Baker has done the Lord's work.
The second phrase of “Monitor climate, forecast weather” means a farmer must pick a variety to plant this spring or pesticide to apply this week. The climate of the next century matters little, but the weather of the coming week or season matters greatly. Monitoring the excursions of weather during the evolution of a new climate and forecasting them even shortly beforehand will make adaptation logical rather than haphazard. The question:
How can monitoring, forecasts and timely information mitigate the harm or heighten the benefits of climate change?
Although the National Weather Service regularly publishes medium to long range weather outlooks, Kuehnast Lecturer Changnon found agricultural managers use them infrequently. They don't use today's predictions in quantitative decisions. Paradoxically, they call for forecasts with accuracy and lead-time already available.
Growing computer power plus knowledge of such things as El Nino will surely improve forecasts for weeks and seasons. Agricultural meteorologists should invent ways for farmers to exploit the improving forecasts.
The analysis and dissemination of weather information to
make it profitable are deficient, whether the information is about climate,
current weather or forecasts. Being
close to farmers, scientists at Stations have a special advantage, even a
responsibility, for remedying this deficiency that could hinder warning and
adapting to climate change.
Removing the stumbling block that inhibits the profitable use of present information is as important as more accurate forecasts.
across the climatic zones of NAFTA from arctic to tropics plus a bent to unite
theory with practice imparts advantages for research in climate change to
So in the end, I kept my promise. I give you something to do about feeding
multitudes, sparing Nature and coping with climate change.
fear we have exhausted our ingenuity, that the gap between average and maximum
yields is closing. The record of farmers
winning the Iowa Masters Contest, however, shows otherwise. The world average
corn yields at the bottom are not closing on the
Other pessimists fear that growing susceptibility to weather will nullify research to improve yields. Duvick, however, found otherwise. He grew corn cultivars from old Reid's Yellow Dent to the newest hybrids. He grew them together in dry 1991, flooded 93 and favorable 92. The advantage of the new varieties was as big in bad years as good. Weather did not cancel what breeding accomplished.
I give you this final, Indian encouragement that
The orange area at the bottom shows the actual ha of wheat grown in
To feed ten billion and spare nature in an uncertain climate, hope makes a better partner than despair and action a better response than paralysis. We have things to do.
Ahmad, M. 1987. Water as a constraint to world food
supplies. In W R Jordan (ed.) Water and water policy in world food supplies.
Bjorkman, O, M Badger and P Armond. 1980. In N C Turner and P J Kramer (eds.) Adaptations of plants to water and high temperature stress. Wiley Interscience, NY. P. 231.
Council for Agricultural Science and Technology (CAST).
Duvick, D N. 1996. What is yield? In Edmeades, G O, M
Banziger, H R Mickelson and C B Pena-Valdivia (eds.). Developing drought- and low N-tolerant maize.
Easterling, W E, M McKenney, N J
Experiment Station Committee on Organization and Policy.
1994. A guide for agricultural
experiment stations to the questions and research anticipating global climate
Frank, A B, J F Power and W O Willis. 1973. Effect of temperature and plant water stress on photosynthesis, diffusion resistance, and leaf water potential in spring wheat. Agron. J 65:777-780
Gash, J H C, and W J Shuttleworth. 1991. Tropical deforestation: albedo and the surface-energy balance. Climatic Change 19:123-133.
Hamilton, C. 1994. In no time at all.
Panel on Policy Implications of Greenhouse Warming. 1992.
Policy implications of greenhouse warming.
Waggoner, P E. 1994. How much land
can ten billion people spare for Nature?
 At the
end of this manuscript, I list “Further
reading”. The booklet referenced
here is “CAST. 1992.
 The diagram of Indian wheat sparing cropland was first published in “How much land can ten billion people spare for Nature?” in 1994. In August 2002, the version above was updated to 2001.