We should replace input-intensity with management-intensity and use more diverse biological systems. By mixing crops and by mixing crops and livestock we can use all of the ecological and biological niches in our production system and thereby increase production. In most cases, this requires more careful management and more people – but people can hardly be a limiting factor on an over-populated planet.
An extract from Global Eating Disorder
From 1700 to 1993 there was an 11 fold increase in human population but only a 5.5 fold increase in cropland area.[i] This was possible because yield per area unit increased rapidly. FAO estimates that, between 1960 and 1999, 78% of the increase in food supply came from higher yields per area unit, 7% from more yields by taking two or even three crops per year instead of one and only 15% came from an increase in area. A very important driver of increase in yield is irrigation. On our farm I think putting in an irrigation system was the most profitable investment we ever made and we farmed in an area with rather good rainfall. Increased cropping intensity has also been very important. In slash and burn cultivation land is only used for one or two years in every twenty, in the old European production systems land was used every one or two years out of three. In Asia today many fields give two crops per year, facilitated by a longer growing season than in temperate climates. A major reason for the yield increases in China in recent decades is this higher intensity in land use. In rare cases one can take three major crops per year, and for specialty crops that grow rapidly, such as lettuce, five to six harvests per year can be possible.
Different parts of the agriculture sector claim credit for yield increases. In reality there are many interlinked factors within the technological and socioeconomic complex in which access to energy and the integration of farming within markets are key drivers.[ii] According to the World Bank’s Development Report 2008, seed breeding has been central; hybrid rice is supposed to explain half of the increase in yields in China from 1975 to 1990 and improved varieties are said to explain 53% of the increased productivity in Punjab (Pakistan). But there can be many other reasons for improved productivity, some of which may not be obvious at first. Roads (!) are said to have improved farm productivity in India by 25%. Better nutrition meant a lot for productivity among African farmers, shedding light on the vicious circle of low yields, low income, little food of low quality, illness, low labor availability, low yields, etc. Twenty percent of the increase in yields is attributed to the use of chemical fertilizers, perhaps a surprisingly small figure considering how often they are said to be so important and even more surprising in the light of the tremendous increase in the use of chemical fertilizers in the same period.[iii] One factor which is often overlooked is that when farmers retire their land, such in the set-aside programs of the European Union or the Conservation Reserve Programme of the United States, they will set aside the least productive land: as such average yield will increase even with no progress whatsoever.
It is still possible to increase yields per area unit in many parts of the world. There was, at the end of the last century, a substantial scope for increasing yields in Argentina, Australia, Canada, Hungary, India, Italy, Poland, Romania, Turkey, Ukraine and the United States. If these countries increased their yields just half-way towards the theoretical optimal, this would generate a 23% increase in the world’s wheat harvest.[iv] In most parts of Africa, small holder farmers harvest 1-2 tons per hectare of maize. They could quite easily double this even without using chemical fertilizers or GMOs.[v] In the article Possible changes to arable crop yields by 2050 researchers from the Rothamstead write “If this [yield gap] is closed and accompanied by improvements in potential yields then there is a good prospect that crop production will increase by approximately 50 percent or more by 2050 without extra land.” Interestingly they also project that the yield of most crops will increase by 13% as a result of increase of carbon dioxide in the atmosphere.[vi]
But the picture is complicated. Lester Brown from the Earth Policy Institute notes that yield increases have tapered off in the more developed parts of the world, and that globally grain yields grew by 2.2 % per year 1950-1990 but only 1.3 % per year in the period 1990-2011.[vii] Three researchers from the University of Nebraska caution us, in an article in Nature Communications, against believing in continued yield increases. In several parts of the world yield increases have reached a plateau, “this seems to be the case in high-yield systems for rice in East Asia (China, the Republic of Korea and Japan), wheat in Northwest Europe (the United Kingdom, France, Germany, the Netherlands and Denmark) and India, and maize in South Europe (Italy and France).[viii]
Progress in maize yields in United States have not decreased, however, notes a report from the USDA; “for example, trend growth rates in Illinois maize yields shifted from about 1 bushel[1] per acre per year from 1940 to 1959 to 1.7 bushels from 1960 onward.[2]” But the authors also caution that “extrapolating past yield trends may help to forecast crop yield growth, but trends differ based on starting points and are not necessarily linear over time.”[ix] Many farmers in United States regularly harvest 10 tons maize per hectare. But wheat yields in the United States have not increased so much as maize: wheat yields increased three fold since the 1940s while maize yields increased five fold. This might be because maize has pushed wheat towards colder, drier and less productive lands. Wheat yields in Unites States are lower than in many other countries, less than half that in Germany, the United Kingdom and France and well below China, Zimbabwe, Uzbekistan, Poland and Mexico. And while maize farmers in United States harvest five times more than their Zambian colleagues, Zambian wheat farmers have more than double the yield of the United States.
The discussion about yield increase, often based on agronomic considerations, tend to largely overlook the effect of economic conditions on yields. While there are certainly biological limits to yields, in most parts of the world economic factors limit yields more than biological factors. Just look at the pepper greenhouse I discussed in the beginning of the book. They produce 30 kg of peppers per square meter, about ten times as much as the average yield in China, the biggest producer of peppers in the world. They do this because they are good growers but also because they invest massive resources into farming, for example they use natural gas equivalent of one liter of oil for every kg of peppers.[x] Ironically they can barely make ends meet, because the highest yield is not necessarily the most profitable. They are an extreme case, but ultimately farmers all over the world are continually making choices about how much to invest. Susan and Fred Mkandawire in Zambia sacrifice maize yield by reducing their weeding or by not applying more fertilizers. They do it knowingly. It simply doesn’t pay to increase their investment; or as expressed by scientists in Nature Communications, “such fine-tuning [to further increase yields] is often difficult to achieve in farmer’s fields, and the associated marginal costs, labor requirements, risks and environmental impacts may outweigh the benefits”.
A problem I already discussed is that high yields often come with high energy input and a high price in the form of eutrophication, pesticide use, the depletion of water and phosphorus and increased erosion. And the question is ‘can we afford this in the long run?’ We should not reduce intensity, but we should replace input-intensity with management-intensity and use more diverse biological systems. By mixing crops and by mixing crops and livestock we can use all of the ecological and biological niches in our production system and thereby increase production. In most cases, this requires more careful management and more people – but people can hardly be a limiting factor on an over-populated planet. Ultimately there is not one recipe for all as conditions differ considerably.
[1] 1 bushel of shelled maize is 25.4012 kg.
[2] The reader should be aware that an increase by a fixed quantity per year means a decline in yield increase as the increase over that of the previous yield will be smaller every year. These differences can, to some extent, explain how different experts reach different conclusions–or how their results are reported by media. ‘Stagnating yields’ in this sense means that the rate of increase (in percentage terms) is stagnating.
[i] Trewavas, A. J. 2001 ‘The Population/Biodiversity Paradox. Plant Physiology January 2001 vol. 125 no. 1 174-179.
[ii] Rundgren, G. 2013 Garden Earth - from hunter and gatherers to global capitalism and thereafter Regeneration.
[iii] World Bank 2007 World Development Report 2007 World Bank.
[iv] Rundgren, G. 2013 Garden Earth - from hunter and gatherers to global capitalism and thereafter Regeneration.
[v] Auberbach, R, G. Rundgren and N. El-Hage Scialabba 2013 Organic Agriculture: African experiences in resilience and sustainability United Nations Food and Agriculture Organization.
[vi] Jaggard, K. W. A. Qi and E.S. Ober 2010 ‘Possible changes to arable crop yields by 2050’ Philosophical Transactions of the Royal Society.
[vii] Brown, L. 2013 Full Planet, Empty Plates: the new geopolitics of food scarcity Earth Policy Institute
[viii] Grassini, P., K.M. Eskridge and K.G. Cassman 2013 ‘Distinguishing between yield advances and yield plateaus in historical crop production trends’ Nature Communications, 17 December 2013.
[ix] Heisey, P. W. 2009 ‘Science, technology, and prospects for growth in US corn yields’ Amber Waves 7 (4). USDA/ERS.
[x] Meyer von Bremen, A-H. and G. Rundgren 2012, Jorden vi äter, Swedish Society for Nature Conservation.
No comments:
Post a Comment