Crosson, P. R. and S. Brubaker. 1982. Resource and Environmental Effects of U.S.
Agriculture. Research paper from Resources for the Future. Washington, D.C.
2.6.1. Description
2.6.1.1. Scale and resolution
The Crosson and Brubaker study analyzes how agriculture will evolve in the U.S.
through the year 2010. Production and environmental effects are analyzed for ten produc- ing regions in the U.S. with attention focused on crop production. Non-U.S. production and consumption through 2010 is also analyzed to establish world demand for U.S. pro- ducts.
2.6.1.2. Approach
The objective of the RFF study is to determine if long-term trends in U.S. agricul- tural production will put pressure on the environment and on land and water resources.
A number of issues are evaluated in the stages leading up to this analysis. T o assess future pressures one needs the levels of resource use and resource availabilities. However resource use depends on choices of inputs which is influenced by agricultural technology and crop yields. Quantities of inputs in turn depend upon output levels which are driven by demand for U.S. agricultural products.
Projections of resource use and environmental effects are derived without the aid of a formal model. Instead, the authors rely on trends in prices, technologies, yields and input use to approximate the evolution of resource use in agriculture. Knowledge of environ- mental effects based on existing and past usage is then used to estimate the environmen- tal implications of the future use projections.
The authors present only one scenario of growth and distribution of population and income from which agricultural demand is derived. A single scenario is also advanced for agricultural supply. Parameters for this scenario are drawn in part from existing litera- ture with adjustments described by the authors. The single scenario approach is chosen t o avoid a "confusing array of projections."
2.6.1.3. Key assumptions and exogenous variables
Each stage of the study's analysis rests upon a number of key assumptions and exo- genous variables. Most important for the demand analysis are assumptions about regional population, income growth and demand elasticities. Future trade patterns, exchange rates and national agricultural policies also influence the demand for each region's output. The stage analyzing future production choices relies heavily on
projections of future relative prices and availabilities of inputs. For the stage of project- ing resource use, assumptions regarding trends in input use and concerning future improvement in input qualities or use techniques are important. For example, fertiliza- tion patterns for crops and regions may change over time and there may be discoveries of better fertilizers or application procedures. Finally, the evaluation of future environmen- tal degradation depends upon assumptions about linkages between resource uses and how they affect the environment.
2.6.1.4. R e s u l t s
The results of the study can be divided into two categories. First are projections regarding resource use and agricultural production. The second category is projections on environmental effects.
Resource and production projections focus on four crop categories which together account for the bulk of resource use and environmental effects in the U.S. These are wheat, feedgrains, soybeans and cotton. Two chapters of the study are devoted t o describing how these crops will be produced. Estimates are presented for future yield lev- els and for technique choices by farmers. Future relative prices of inputs are discussed as the factors determining input mix and productivity.
The study presents estimates of resource use by crop and by region. Resources and inputs are grouped in the broad categories of cropland, fertilizers, insecticides, herbicides and irrigation. Use estimates are derived by combining projections of outputs, techniques and yields with data on availability and use trends of the resources. Land projections are based mostly on demand and supply considerations whereas fertilizer and pesticide projec- tions rely largely on marginal effectiveness of the inputs and on developments in produc- tion techniques.
Environmental effects of agriculture are traced in the study from the projected resource uses. Future fertilizer usage is discussed with respect t o nitrate levels in drinking water and eutrophication of lakes and ponds. Pesticide use is evaluated in terms of threats t o humans from toxins. Projections for future irrigation are linked with both salinity of surface waters and the build up of salts on croplands. Finally, cropland conversion and cropping techniques are discussed in relation to soil erosion. The environmental impacts chapter stresses the high degree of uncertainty in ( i ) linking resource use causally to environmental degradation, and (ii) limiting the discussion to problems currently identified.
2.6.2. E v a l u a t i o n
2.6.2.1. Sensitivity analysis
Sensitivity of the results t o changes in the assumptions is not directly discernable due t o the discursive nature of the presentation. It is difficult for a reader t o alter a set of assumptions and trace through the effects. However it is possible to describe the type of effects that would result.
Altering the population, income, income elasticity and production policy assump tions would act t o scale the demand for agriculture and the study's results up or down with little effect on the interlinking stages or relationships. A change in agricultural trade patterns however may lead t o a major shift in demand and move the U.S. away from export oriented crop production.
A change in assumptions regarding input prices, availabilities or qualities may have a significant effect on resource use and the environment. For example cheaper or better non-land inputs could lead t o land intensive expansion of production, a reversal of the
extensive mode of expansion described in the study. The resulting new input use rates and techniques would change the scale and nature of environmental effects.
Results of the study are perhaps most sensitive to assumptions regarding linkages between resource use and the environment. New assumptions introducing additional damaging effects or eliminating links could dramatically alter the results. Given the uncertainty about these interactions such new assumptions are not unrealistic. However discoveries revealing major new degradations would probably also alter the control regu- lations, production technologies and resource use rates.
2.6.2.2. Sources of s u r p r i s e
We were also interested in the sensitivity of studies t o surprises or discontinuities in trends not discernable from current trends. Crosson and Brubaker forecast trends into the future based largely on present trends and current knowledge about possible changes.
No attempt is made t o incorporate surprise type shocks into their study. Such shocks can be introduced a t each stage of the study. On the demand end, changes in consumption habits or a reordering of trade policies and patterns could significantly alter agricultural demand. The next stage's estimates for production techniques and crop yields are extremely sensitive t o breakthroughs in technological research. New crop varieties or fer- tilization techniques could reverse input use and yield trends. These trends also depend on input prices which are projected to increase steadily throughout the thirty year period.
Unforeseen scarcities or market interventions can suddenly change these input prices.
Production techniques and input use are also sensitive t o major pest or disease outbreaks.
Finally, as mentioned earlier, the environmental impacts are derived in the study from currently identified damages. It is possible that present input usage is causing an undiscovered type of damage. Crosson and Brubaker mention this possibility in passing with respect to pesticide effects on soil micro- organisms.
2.6.2.3. Environmental c o m p o n e n t s i n the RFF s t u d y
Unlike most of the other agricultural studies described in this section the RFF study directly addresses issues of environmental degradation resulting from agricultural develop ment. Environmental quality is approached through projections of both resource use and production technologies. For example water quality is closely related t o actual quantities of fertilizers, pesticides and irrigation water used in agriculture. Equally important how- ever is the way these inputs are used including such considerations as use rates per acre and the method and timing of application. By combining estimates of both quantities and techniques for specific crops and regions, the study draws conclusions about possible threats of eutrophication, nitrate levels, toxins, and salinity.
Land quality is addressed principally through the soil erosion issue. As with water quality, erosion possibilities are derived from estimates of both the quantity of land that is cultivated and how that land is used. Salt accumulations with irrigation and possible damages t o soil micro-organisms from insecticides are also discussed.
Land and water quantities are not dealt with explicitly but are implicit in the dis- cussion of future relative prices of inputs which in turn determine input use. Scarcities of energy and mineral resources are handled in the same way. Major loss of soil and water
Indicators of economic development are used as exogenous inputs t o the RFF study.
Income growth and national self sufficiency enter the study t o project world demand and supply which are then used in estimating the demand for U.S. agricultural output. The issues of air quality, climate change, equity, and nutrition are not addressed in the Cros- son and Brubaker study.
2.6.2.4. Relevance to long-term, large-scale environmental studies
The study is probably most useful for studies of development-environment interac- tions in defining an approach to identify agricultural activities relevant t o the environ- ment. It focuses not only on what resources are used but also on how and where they are used. This information is critical in evaluating the environmental impacts of agriculture.
The interim steps leading to the environmental impact chapter identify the types of ques- tions that must be asked in any environmental study. Of particular value are descriptions of how and why various production techniques and input mixes will be selected by farm- ers. The regional choices of crops, inputs and techniques are also important. This analyt- ical procedure can be employed by others with interests in different regions or with differing initial assumptions of population, incomes or technical change.
For the immediate purpose of evaluating long-term sustainability of worldwide agri- cultural development the study leaves many important questions unanswered. Two key limitations are the focus on the United States only and the selection of a single develop ment scenario. One cannot look up or extrapolate for global environmental effects or easily incorporate new scenario assumptions. Instead, the analysis must be repeated.
Also the study does not deal with longer term effects of agriculture on the environ- ment. For instance, levels of contamination that may not pose problems in the year 2010 may accumulate t o significant proportions by 2030 or 2040. This may be true for nitrification and eutrophication levels or the effects of organophosphorus pesticides.
Another uncertainty is the long run availability of resource inputs. Crosson and Brubaker find U.S. resources adequate through 2010 but what about sustainability beyond that year given water and land degradation? Also environmental problems elsewhere in the world could greatly expand demand for U.S. output. With international trade in agri- cultural goods the issue is one of global not regional resource availability.
2.6.3. Reviews
1) Batie, S. in Food Policy. 9,1:85. Feb 1984.
A description of the study's contents and analytical approach t o the problem.
Emphasizes that "the book is designed for professionals" and not recommended for a
"lay reader."
2) Beattie, B. in American Journal of Agricultural Economics. 65,4:838. Nov 1983.
A description of the objectives and contents of the study. Beattie criticizes the choice of rejecting a formal modeling approach. Such an approach would clarify "the underlying cause and effect relationships and provide a more structured framework for the critical reader in assessing the validity of the results." He also comments that the single scenario approach "implies a far greater level of precision than is war- ranted."