Mailing 15 May 2012

Article: organic and conventional yields

Another article that looks at organic versus conventional yields. It compares yields in both developed and developing world contexts and argues a. the case for a more nuanced approach to considering yield variations and b. for less dogmatism in the debate on sustainable agriculture.

Re. their method, in order to criticisms made of an earlier study by Badgley et al (see here) they (1) restricted their analysis to studies of ‘truly’ organic systems, defined as those with certified organic management or non-certified organic management, following the standards of organic certification bodies; (2) only included studies with comparable spatial and temporal scales for both organic and conventional systems; and (3) only included studies reporting (or from which they could estimate) sample size and error. Conventional systems were either high- or low-input commercial systems, or subsistence agriculture. Sixty-six studies met these criteria, representing 62 study sites, and reporting 316 organic-to-conventional yield comparisons on 34 different crop species

Reference and summary as follows:

Seufert V, Ramankutty N and Foley J A (2012).  Letter: Comparing the yields of organic and conventional agriculture, Nature doi:10.1038/nature11069

“Numerous reports have emphasized the need for major changes in the global food system: agriculture must meet the twin challenge of feeding a growing population, with rising demand for meat and high-calorie diets, while simultaneously minimizing its global environmental impacts. Organic farming—a system aimed at producing food with minimal harm to ecosystems, animals or humans—is often proposed as a solution.However, critics argue that organic agriculture may have lower yields and would therefore need more land to produce the same amount of food as conventional farms, resulting in more widespread deforestation and biodiversity loss, and thus undermining the environmental benefits of organic practices. Here we use a comprehensive meta-analysis to examine the relative yield performance of organic and conventional farming systems globally. Our analysis of available data shows that, overall, organic yields are typically lower than conventional yields. But these yield differences are highly contextual, depending on system and site characteristics, and range from 5% lower organic yields (rain-fed legumes and perennials on weak acidic to weak-alkaline soils), 13% lower yields (when best organic practices are used), to 34% lower yields (when the conventional and organic systems are most comparable). Under certain conditions— that is, with good management practices, particular crop types and growing conditions—organic systems can thus nearly match conventional yields, whereas under others it at present cannot. To establish organic agriculture as an important tool in sustainable food production, the factors limiting organic yields need to be more fully understood, alongside assessments of the many social, environmental and economic benefits of organic farming systems."


“In short, these results suggest that today’s organic systems may nearly rival conventional yields in some cases—with particular crop types, growing conditions and management practices—but often they do not. Improvements in management techniques that address factors limiting yields in organic systems and/or the adoption of organic agriculture under those agroecological conditions where it performs best may be able to close the gap between organic and conventional yields.

Although we were able to identify some factors contributing to variations in organic performance, several other potentially important factors could not be tested owing to a lack of appropriate studies. For example, we were unable to analyse tillage, crop residue or pest management. Also,most studies included in our analysis experienced favourable growing conditions, and organic systems were mostly compared to commercial high-input systems (which had predominantly above-average yields in developing countries). In addition, it would be desirable to examine the total human-edible calorie or net energy yield of the entire farm system rather than the biomass yield of a single crop species. To understand better the performance of organic agriculture, we should: (1) systematically analyse the long-term performance of organic agriculture under different management regimes; (2) study organic systems under a wider range of biophysical conditions; (3) examine the relative yield performance of smallholder agricultural systems; and (4) evaluate the performance of farming systems through more holistic system metrics.

As emphasized earlier, yields are only part of a range of economic, social and environmental factors that should be considered when gauging the benefits of different farming systems. In developed countries,the central question is whether the environmental benefits of organic crop production would offset the costs of lower yields (such as increased food prices and reduced food exports). Although several studies have suggested that organic agriculture can have a reduced environmental impact compared to conventional agriculture, the environmental performance of organic agriculture per unit output or per unit input may not always be advantageous. In developing countries, a key question is whether organic agriculture can help alleviate poverty for small farmers and increase food security. On the one hand, it has been suggested that organic agriculture may improve farmer livelihoods owing to cheaper inputs, higher and more stable prices, and risk diversification.

On the other hand, organic agriculture in developing countries is often an export-oriented system tied to a certification process by international bodies, and its profitability can vary between locations and years. There are many factors to consider in balancing the benefits of organic and conventional agriculture, and there are no simple ways to determine a clear ‘winner’ for all possible farming situations.”

The article ends with this eminently sensible comment “… instead of continuing the ideologically charged ‘organic versus conventional’ debate, we should systematically evaluate the costs and benefits of different management options. In the end, to achieve sustainable food security we will probably need many different techniques—including organic, conventional, and possible ‘hybrid’ systems—to produce more food at affordable prices, ensure livelihoods for farmers, and reduce the environmental costs of agriculture.”

You can download the paper here (subscription needed).

An earlier paper by two of these three authors (Foley and Ramankutty) is also worth reading – and is summarised on the FCRN website here.

Two studies on biodiversity

Two studies, one in Nature and the other in Science present evidence to demonstrate the importance of biodiversity in maintaining long term ecosystem productivity and sustainability.

The paper in Science presents data from two 14-year field experiments which looked at how the effect of diversity on plant productivity changed over the long-term.  According to one of the paper’s authors "Prior shorter-term studies, most about two years long, found that diversity increased productivity, but that having more than six or eight species in a plot gave no additional benefit," Reich says. However this study finds that over a 14-year time span, all 16 species in the most diverse plots contributed more and more The study also found that different species have different ways of acquiring water, nutrients and carbo, and of maintaining them in an ecosystem.

Reference and abstract as follows:

Reich P B, Tilman D, Isbell F, Mueller K, Hobbie S E, Flynn D F B and Eisenhauer N (2012). Impacts of Biodiversity Loss Escalate Through Time as Redundancy Fades, Science 2012: 589-592.DOI:10.1126/science.1217909

Plant diversity generally promotes biomass production, but how the shape of the response curve changes with time remains unclear. This is a critical knowledge gap because the shape of this relationship indicates the extent to which loss of the first few species will influence biomass production. Using two long-term (≥13 years) biodiversity experiments, we show that the effects of diversity on biomass productivity increased and became less saturating over time. Our analyses suggest that effects of diversity-dependent ecosystem feedbacks and interspecific complementarity accumulate over time, causing high-diversity species combinations that appeared functionally redundant during early years to become more functionally unique through time. Consequently, simplification of diverse ecosystems will likely have greater negative impacts on ecosystem functioning than has been suggested by short-term experiments.

You can access the paper here (subscription only).

The paper in Nature bases its conclusions on a data synthesis which finds that species loss ranks among the major drivers of primary production and decomposition - key processes involved in the carbon cycle and the provisioning of many ecosystem services.  This effect appears to be as significant as other forms of environmental stress, such as climate change and pollution.

Reference and abstract as follows:

Hooper D U, Adair E C, Cardinale B J, Byrnes J E K, Hungate B A, Matulich K L, Gonzalez A, J Duffy J E, Gamfeldt L, O’Connor M I (2012). A global synthesis reveals biodiversity loss as a major driver of ecosystem change. Nature, 2012; DOI: 10.1038/nature11118

Evidence is mounting that extinctions are altering key processes important to the productivity and sustainability of Earth’s ecosystems. Further species loss will accelerate change in ecosystem processes, but it is unclear how these effects compare to the direct effects of other forms of environmental change that are both driving diversity loss and altering ecosystem function. Here we use a suite of meta-analyses of published data to show that the effects of species loss on productivity and decomposition - two processes important in all ecosystems - are of comparable magnitude to the effects of many other global environmental changes. In experiments, intermediate levels of species loss (21–40%) reduced plant production by 5–10%, comparable to previously documented effects of ultraviolet radiation and climate warming. Higher levels of extinction (41–60%) had effects rivalling those of ozone, acidification, elevated CO2 and nutrient pollution. At intermediate levels, species loss generally had equal or greater effects on decomposition than did elevated CO2 and nitrogen addition. The identity of species lost also had a large effect on changes in productivity and decomposition, generating a wide range of plausible outcomes for extinction. Despite the need for more studies on interactive effects of diversity loss and environmental changes, our analyses clearly show that the ecosystem consequences of local species loss are as quantitatively significant as the direct effects of several global change stressors that have mobilized major international concern and remediation efforts.

You can access the article here (subscription only).

Coverage of the study’s findings can be found here.

Global Food Policy Report - IFPRI

The International Food Policy Research Institute has launched its inaugural Global Food Policy Report, the first in a new annual series. The Report provides a comprehensive overview of major policy changes at the global, regional, national, and local levels, as well as their significance for food and nutrition security.   The report covers trends and policies in relation to: global food prices and price volatility; disasters; climate change, biofuels, the agri-nutrition nexus; land; emerging players (industrialising economies, major philanthropists, the G20; public-private partnerships); and regional developments (Pages 4-6 of the report provide a useful timeline of key developments and events).

It points to somehigh-priority areas for action in 2012. First, the G20 should take further steps to rein in food price volatility by, for example, doing more to reduce the competition between biofuel and food production and to discourage trade restrictions that exacerbate price swings. Second, the international community should consolidate global and regional agricultural growth strategies and create or strengthen the institutions and capacities needed to make these strategies work. In particular, this year’s G8 summit should work to ensure that the industrial countries meet their financial commitment in support of a country-led development process for achieving food security in developing countries. Third, participants in the Rio+20 meeting should integrate economic, social, and environmental sustainability efforts and commit to concrete action to meet the long-term challenges of development, including poor nutrition, degraded soils, and scarce water. Finally, a broad intersectoral coalition should work together to address issues related to nutrition, food, and health.

You can read an overview, access the press materials or download the full report here.

People and the planet: Royal Society Report

The Royal Society has published a new report arguing that the most developed and the emerging economies must stabilise consumption levels, then reduce them, to help the poorest 1.3 billion people to escape absolute poverty through increased consumption. Alongside this, education and voluntary family planning programmes must be supported internationally to stabilise global population. Key recommendations are as follows:

  • The international community must bring the 1.3 billion people living on less than $1.25 per day out of absolute poverty, and reduce the inequality that persists in the world today. This will require increased per capita consumption for this group, allowing improved nutrition and healthcare, and reduction in family size in countries with high fertility rates. It will require focused efforts in key policy areas including economic development, education, family planning and health.
  • In the most developed and the emerging economies, unsustainable consumption must be urgently reduced. This will entail scaling back or radical transformation of damaging material consumption and emissions and the adoption of sustainable technologies, and is critical to ensuring a sustainable future for all. At present, consumption is closely linked to economic models based on growth. Improving the wellbeing of individuals so that humanity flourishes rather than survives requires moving from current economic measures to fully valuing natural capital. Decoupling economic activity from material and environmental throughputs is needed urgently for example by reusing equipment and recycling materials, reducing waste, obtaining energy from renewable sources, and by consumers paying for the wider costs of their consumption. Changes to the current socio-economic model and institutions are needed to allow both people and the planet to flourish by collaboration as well as competition during this and subsequent centuries. This requires farsighted political leadership concentrating on long term goals.
  • Global population growth needs to be slowed and stabilised, but this should by no means be coercive. A large unmet need for contraception remains in both developing and developed countries. Voluntary family planning is a key part of continuing the downward trajectory in fertility rates, which brings benefits to the individual wellbeing of men and women around the world. In the long term a stabilised population is an essential prerequisite for individuals to flourish. Education will play an important role: well educated people tend to live longer healthier lives, are more able to choose the number of children they have and are more resilient to, and capable of, change. Education goals have been repeatedly agreed by the international community, but implementation is poor.
  • Population and the environment should not be considered as two separate issues. Demographic changes, and the influences on them, should be factored into economic and environmental debate and planning at international meetings, such as the Rio+20 Conference on Sustainable Development and subsequent meetings.

Other recommendations focus on:

  • The potential for urbanisation to reduce material consumption
  • Removing barriers to achieve high-quality primary and secondary education for all
  • Undertaking more research into the interactions between consumption, demographic change and environmental impact
  • Implementing comprehensive wealth measures
  • Developing new socio-economic systems.

You can download the report here.

Greenhouse Gas Action Plan: one year on progress report

The UK agricultural industry has published its first report on progress made in delivering its Greenhouse Gas Action Plan. The report says that the sector’s plans for the provision of an innovative pilot Farm Efficiency Hub – an electronic library service to support farm advisers, farmers and land managers – are advancing. It has also set out plans for its next phase – the Delivery Plan, which features 25 actions through to 2015. These cover strategic coordination, communication, management skills and advice, crop nutrient management, soil and land management, livestock nutrition; livestock health and fertility, energy efficiency and renewables.

The NFU’s press release is here, and you can download both the full report and a summary version here.

LCIRAH workshop: 'The Role of Agricultural and Food Systems Research in Combating Chronic Disease for Development'

The Leverhulme Centre for Integrative Research on Agriculture and Health (LCIRAH) is organising a two-day workshop in London during 2nd and 3rd July 2012 on 'The Role of Agricultural and Food Systems Research in Combating Chronic Disease for Development'.

Confirmed speakers/discussants at the workshop include Srinath Reddy, John Barrett, Per Pinstrup-Andersen, Ismael Thiam, Marion Nestle, Marie Ruel, John McDermott and Gert Meijer, among others.

Registration opens 8th May and closes 22nd June.

The workshop is free and open to all, but space is limited. For more information see here.

Useful presentation: global burden of chronic diseases

This World Health Organisation ppt provides an overview of the causes, trends and impacts of chronic diseases worldwide, and points out very strongly that it’s increasingly a problem affecting poor people in the developing world. You can download the presentation here.

Fully Funded PhD Studentship: Models to support policy-making for a secure and sustainable food supply

The Centre for Environmental Strategy at the University of Surrey invites application for a fully funded PhD studentship associated with the interdisciplinary research project ERIE (Evolution and Resilience of Industrial Ecosystems), a joint venture with the Departments of Sociology, Mathematics and Computing.

The ERIE case study will focus on developing tools that will enable policy makers to envisage scenarios for national, regional and international food supply chains and thus be able to make more informed policy decisions. Achieving this requires not only a focus on agricultural production and food outputs, but also a systems wide understanding to ensure availability, access and efficient utilisation. Consideration of the complex interdependencies between the environmental, economic and social factors involved in these systems is essential for informing policies to promote resilient food supply chains.

The PhD student will work as part of the ERIE team on the food case study, and will focus on creating a model (or models) to support policy-making. There is considerable scope for the candidate to define the precise topic. Possible examples include the competition between production of food and the increasing demands of the bio-based economy, the security of phosphorous supply, or the resilience of food supply chains to shocks in food prices. Identifying pressure points in the food system where supply chains might be at risk, investigating food consumption and food supply chain related datasets, and determining points of intervention at economic, physical, political and cultural levels are essential for exploring possible policy options to increase the resilience of food systems. For further information on this studentship and how to apply visit post 8,724 on the University's Employment Opportunities pages.