THIRD WORLD NETWORK INFORMATION SERVICE ON SUSTAINABLE AGRICULTURE
Re: Strengthening Resilience of Farming Systems
The UN Conference on Trade and Environment (UNCTAD) launched its Trade and Environment Review 2013 on 18 September 2013 (see TWN Agriculture Info: Making Agriculture Truly Sustainable for Food Security in a Changing Climate, 19 September 2013). The report highlights the drastic changes needed in agriculture to combat hunger and environmental degradation.
One of the commentaries was on “Strengthening resilience of farming systems: A prerequisite for sustainable agricultural production”. The authors argue that agroecologically managed systems are best placed to cope with future challenges because they exhibit high levels of diversity and resilience while delivering reasonable yields and ecosystem functions. Such systems are exemplified by the many traditional farming systems that are still prevalent in developing countries, and which can serve as models of sustainability and resilience.
In particular, resilience in agricultural systems is a function of the level of diversity within the agricultural ecosystem. It is therefore essential that strategies for an adaptive response to climate change focus on breaking away from the monoculture nature that is prevalent in modern agroecosystems. Instead, diversified farming systems allow complementary interactions that boost yields with low inputs, thus increasing profits, and, given the diversity of crops, minimizing production risks.
Given the resilience of diversified small farming systems, the authors call for a deeper understanding of the agroecological features of traditional agroecosystems as a matter of urgency, as this can serve as the foundation for the design of agricultural systems that are resilient to climate change.
The commentary is reproduced below. The Trade and Environment Review 2013 is available at http://unctad.org/en/pages/PublicationWebflyer.aspx?publicationid=666
Strengthening resilience of farming systems: A prerequisite for sustainable agricultural production
Traditional farming systems have enabled farmers to generate sustained yields to meet their subsistence needs in the context of climatic variability. Part of this performance is linked to the high levels of agrobiodiversity exhibited by traditional agroecosystems. Strategies to enhance diversity in agroecosystems include support to family agriculture and to smallholders, and dynamic conservation of globally important agricultural heritage systems. Diversification is therefore an important farm strategy for managing production risk in farming systems. Strategies to restore diversity in modern farming systems include promoting seed diversity, crop rotations, cover crops, intercropping and crop/livestock mixing. Diversified farming systems managed with modern equipment allow complementary interactions that boost yields with low inputs, thus increasing profits, and, given the diversity of crops, minimizing production risks.
Today, a major challenge facing humanity is how to achieve a sustainable agriculture that provides sufficient food and ecosystem services for present and future generations in an era of climate change, rising fuel costs, social tensions caused by food price hikes, financial instability and accelerating environmental degradation. The challenge is compounded by the fact that the majority of the world’s arable land is under "modern" monoculture systems of maize, soybean, rice, cotton and others, which, due to their ecological homogeneity, are particularly vulnerable to climate change as well as biotic stresses. Little has been done to enhance the adaptability of industrial agroecosystems to changing patterns of precipitation, temperatures and extreme weather events (Rosenzweig and Hillel, 2008). This realization has led many experts to suggest that the use of ecologically based management strategies may represent a robust means of increasing the productivity, sustainability and resilience of agricultural production while reducing its undesirable socio-environmental impacts (Altieri, 2002; de Schutter, 2010).
Observations of agricultural performance after extreme climatic events during the past two decades have revealed that resilience to those events is closely linked to the level of on-farm biodiversity (Lin, 2011). Most scientists agree that a basic attribute of agricultural sustainability is the maintenance of agroecosystem diversity in the form of spatial and temporal arrangements of crops, trees, animals and associated biota. Increasingly, research suggests that agroecosystem performance and stability is largely dependent on the level of plant and animal biodiversity present in the system and its surrounding environment (Altieri and Nicholls, 2004). Biodiversity performs a variety of ecological services beyond the production of food, including recycling of nutrients, regulation of microclimate and of local hydrological processes, suppression of undesirable organisms and detoxification of noxious chemicals. Because biodiversity-mediated renewal processes and ecological services are largely biological, their continued functioning depends upon the maintenance of biological integrity and diversity in agroecosystems. In general, natural ecosystems appear to be more stable and less subject to fluctuations in yield and in the populations of organisms making up the community. Ecosystems with higher diversity are more stable because they exhibit greater resistance, or the ability to avoid or withstand disturbances, and greater resilience, or the ability to recover following disturbances.
Biodiversity enhances ecosystem functions because those components that appear redundant at one point in time may become important when some environmental change occurs. What is important is that when environmental change occurs, the redundancies of the system enable continued ecosystem functioning and provisioning of services (Vandermeer et al., 1998).
Traditional farming systems, which still persist in many developing countries, offer a wide array of management options and designs that enhance functional biodiversity in crop fields, and consequently support the resilience of agroecosystems (Uphoff, 2002; Toledo and Barrera-Bassals, 2009). The myriad of traditional systems are a globally important, ingenious agricultural heritage which reflects the value of the diversity of agricultural systems that are adapted to different environments. They tell a fascinating story of the ability and ingenuity of humans to adjust and adapt to the vagaries of a changing physical and material environment from generation to generation. Whether recognized or not by the scientific community, this ancestral knowledge constitutes the foundation for actual and future agricultural innovations and technologies. The new models of agriculture that humanity will need in the immediate future should include forms of farming that are more ecological, biodiverse, local, sustainable and socially just. Therefore, they will necessarily have to be rooted in the ecological rationale of traditional small-scale agriculture, which represents long-established, successful and adaptive forms of agriculture (Koohafkan and Altieri, 2010).
Small farms as models of resilience
In continuously coping with extreme weather events and climatic variability through centuries, farmers living in harsh environments in Africa, Asia and Latin America have developed and/or inherited complex farming systems managed in ingenious ways. These have allowed small farming families to meet their subsistence needs in the midst of environmental variability without depending much on modern agricultural technologies (Denevan, 1995). The continued existence of millions of hectares under traditional farming is living proof of a successful indigenous agricultural strategy, which is a tribute to the “creativity” of small farmers throughout the developing world (Wilken, 1987). Today, well into the first decade of the twenty-first century, millions of smallholders, family farmers and indigenous people are continuing to practice resource-conserving farming. Such traditional systems are testament to the remarkable resilience of agroecosystems to continuous environmental and economic change, which, despite changes, continue to contribute substantially to agrobiodiversity conservation and food security at local, regional and national levels (Netting, 1993).
However, climate change can pose serious problems for the majority of the 370 million of the world’s poorest, who live in areas often located in arid or semi-arid zones, and in ecologically vulnerable mountains and hills (Conway, 1997). In many countries, more and more people, particularly those at lower income levels, are now forced to live in marginal areas (i.e. floodplains, exposed hillsides, arid or semi-arid lands), where they are at risk from the negative impacts of climate variability. Even minor changes in climate can have disastrous impacts on the lives and livelihoods of these vulnerable groups. The implications for food security could be very profound, especially for subsistence farmers living in remote and fragile environments that are likely to produce very low yields. These farmers depend on crops that could be badly affected, such as maize, beans, potatoes and rice. Despite the serious implications of predictions, data represent only a broad brush approximation of the effects of climate change on small-scale agriculture. In many cases those data ignore the adaptive capacity of small farmers who use several agroecological strategies and socially mediated solidarity networks to cope with and even prepare for extreme climatic variability (Altieri and Koohafkan, 2008).
Three studies assessing agricultural performance after extreme climatic events reveal the close link between enhanced agro-biodiversity and resilience to extreme weather events. A survey conducted in Central American hillsides after Hurricane Mitch showed that farmers engaged in diversification practices, such as cover crops, intercropping and agroforestry, suffered less damage than their neighbours who practiced conventional monoculture. The survey, spearheaded by the Campesino a Campesino movement, mobilized 100 farmer-technician teams to carry out paired observations of specific agroecological indicators on 1,804 neighbouring sustainable and conventional farms. The study spanned 360 communities and 24 departments in Guatemala, Honduras and Nicaragua. It found that plots where farmers adopted sustainable farming practices had 20 to 40 per cent more topsoil, greater soil moisture and less erosion, and experienced smaller economic losses than their conventional neighbours (Holt-Gim้nez, 2002). Similarly in Sotonusco, Chiapas, coffee systems exhibiting high levels of vegetation complexity and plant diversity suffered less damage from Hurricane Stan than more simplified coffee systems (Philpott et al., 2008). And in Cuba, 40 days after Hurricane Ike hit the country in 2008, researchers conducting a farm survey in the provinces of Holguin and Las Tunas found that diversified farms exhibited losses of 50 per cent compared to 90 or 100 per cent in neighbouring monoculture farms. Likewise, agroecologically managed farms showed a faster recovery of productivity (80–90 per cent 40 days after the hurricane) than monoculture farms (Rosset et al., 2011). All three studies emphasize the importance of enhancing plant diversity and complexity in farming systems to reduce vulnerability to extreme climatic events. Since many peasants commonly manage polycultures and/or agroforestry systems, their knowledge and practices could provide a key source of information on adaptive capacity centredon the selective, experimental and resilient capabilities of those farmers in dealing with climatic change.
Given the resilience of diversified small farming systems, understanding the agroecological features of traditional agroecosystems is an urgent matter, as this can serve as the foundation for the design of agricultural systems that are resilient to climate change (Altieri and Koohafkan 2008).
Restoring agrobiodiversity in modern agroecosystems
Since the modernization of agriculture, farmers and researchers have been faced with a major ecological dilemma arising from the homogenization of agricultural systems, namely the increased vulnerability of crops to pests and diseases, and now to climatic variability. Both these phenomena can be devastating in genetically uniform, large-scale, monoculture conditions. Monocultures may offer short-term economic advantages to farmers, but in the long term they do not represent an ecological optimum. Rather, the drastic narrowing of cultivated plant diversity has put the world’s food production in greater peril (Perfecto, Vandermeer and Wright, 2009).
Given the new climate change scenarios predicted over the next two decades or so by some scientists (e.g. Rosenzweig and Hillel, 2008), the search for practical steps to break the monoculture nature of modern agroecosystems, and thus reduce their ecological vulnerability, is imperative. As traditional farmers have demonstrated with farming systems that stood the test of time, restoring agricultural biodiversity at the field and landscape level is key to enhancing resilience. Greater diversity of species is probably needed to reduce temporal variability of ecosystem processes in changing environments. The most obvious advantage of diversification is reduced risk of total crop failure due to invasions of unwanted species and/or climatic variability, as larger numbers of species reduce temporal variability in ecosystem processes in changing environments (Loreau et al., 2011). Studies conducted in grassland systems suggest that there are no simple links between species diversity and ecosystem stability. Experiments conducted in grassland plots conclude that functionally different roles represented by plants are at least as important as the total number of species in determining processes and services in ecosystems (Tilman et al., 2001). This latest finding has practical implications for agroecosystem management. If it is easier to mimic specific ecosystem processes rather than attempting to duplicate all the complexity of nature, then the focus should be placed on incorporating a particular biodiversity component that plays a specific role, such as plants that fix nitrogen, provide cover for soil protection or harbour resources for natural enemies of insect pests.
Contemporary notions of modern mechanized farming emphasize the necessity of monocultures. There is little question, however, that given sufficient motivation, appropriate technology could be developed to mechanize multiple cropping systems (Horwith, 1985). Simpler diversification schemes based on 2 or 3 plant species may be more amenable to large-scale farmers and can be managed using modern equipment. One such scheme is strip intercropping, which involves the production of more than one crop in strips that are narrow enough for the crops to interact, yet wide enough to permit independent cultivation. Agronomically beneficial strip intercropping systems have usually included corn or sorghum, which readily respond to higher light intensities (Francis et al., 1986). Studies with corn and soybean strips 4 to 12 rows wide demonstrated increased corn yields (5 to 26 per cent higher) and decreased soybean yields (8.5 to 33 per cent lower) as strips got narrower. Alternating corn and alfalfa strips provided greater gross returns than single crops. Strips of 20 ft. (approximately 6.1 meters) width were the most advantageous, with substantially higher economic returns than the single crops (West and Griffith, 1992). This advantage is critical for farmers who have debt-to-asset ratios of 40 per cent or higher ($40 of debt for every $100 of assets). Such a level has already been reached by more than 11–16 per cent of farmers in the mid-western United States who desperately need to cut costs of production by adopting diversification strategies.
Legumes intercropped with cereals is a key diversification strategy, not only because of their provision of nitrogen, but also because the mixtures enhance soil cover, smother weeds and increase nutrients (e.g. potassium, calcium and magnesium) in the soil through the addition of biomass and residues to the soil. Such intercropping systems also increase soil microbial diversity such as vesicular arbuscular mycorrhizae (VAM) fungi which facilitate phosphorous transfer to the crops (Machado, 2009). In the case of adverse weather conditions, such as a delay in the onset of rains and/or failure of rains for a few days, weeks or during the cropping period, an intercropping system provides the advantage that at least one crop will survive to give economic yields, thereby serving as the necessary insurance against unpredictable weather. Polycultures exhibit greater yield stability and lower productivity declines during a drought than monocultures. This was well demonstrated by Natarajan and Willey (1986) who examined the effects of drought on polycultures by manipulating water stress on intercrops of sorghum (Sorghum bicolor) and peanut (Arachis spp.), millet (Panicum spp.) and peanut, and sorghum and millet. All the intercrops consistently provided greater yields at five levels of moisture availability, ranging from 297 to 584 mm of water applied over the cropping season. Interestingly, the rate of over-yielding actually increased with water stress, such that the relative differences in productivity between monocultures and polycultures became more accentuated as stress increased.
No-till row crop production is also promising, given its soil conservation and improvement potential, but it is highly dependent on herbicides. However, there are some organic farmers who practice it without synthetic herbicides. A breakthrough occurred with the discovery that certain winter annual cover crops, notably cereal rye and hairy vetch, can be killed by mowing at a sufficiently late stage in their development and cutting close to the ground. These plants generally do not re-grow significantly, and the clippings form anin situ mulch through which vegetables can be transplanted with no or minimal tillage. The mulch hinders weed seed germination and seedling emergence, often for several weeks. As they decompose, many cover crop residues can release allelopathic compounds that may suppress weed growth (Moyer, 2010) by means of phytotoxic substances that are passively liberated through decomposition of plant residues. There are several green manure species that have a phytotoxic effect which is usually sufficient to delay the onset of weed growth until after the crop’s minimum weed-free period. This makes post-plant cultivation, herbicides or hand weeding unnecessary, yet exhibits acceptable crop yields. Tomatoes and some late-spring brassica plantings perform especially well, and some large-seeded crops such as maize and beans can be successfully direct-sown into cover crop residues. Not only can cover crops planted in no-till fields fix nitrogen in the short term; they can also reduce soil erosion and mitigate the effects of drought in the long term, as the mulch conserves soil moisture. Cover crops build vertical soil structure as they promote deep macropores in the soil, which allow more water to penetrate during the winter months and thus improve soil water storage.
There is general agreement at the international level on the urgent need to promote a new agricultural production paradigm in order to ensure the production of abundant, healthy and affordable food for an increasing human population. This challenge will need to be met with a shrinking arable land base, with less and more expensive petroleum, increasingly limited supplies of water and nitrogen, and at a time of rapidly changing climate, social tensions and economic uncertainty (IAASTD, 2009). The only agricultural system that will be able to cope with future challenges is one that will exhibit high levels of diversity and resilience while delivering reasonable yields and ecosystem services. Many traditional farming systems still prevalent in developing countries can serve as models of sustainability and resilience.
Resilience in agricultural systems is a function of the level of diversity within the agricultural ecosystem. It is therefore essential that strategies for an adaptive response to climate change focus on breaking away from the monoculture nature of modern agroecosystems. Small changes in the management of industrial systems, such as intercropping and/or use of rotational cover cropping in no-till systems, can substantially enhance the adaptive capacity of cropping systems. Weather extremes, including local drought and flooding, are predicted to become more common as a result of rapid climate change. Environmentally responsible water management will therefore have to be a critical part of sustainable agriculture in the future. Agroecological strategies for conserving water include choosing water-efficient crops, resource-conserving crop rotations, enhancing soil organic matter and intercropping systems.
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