Organic Agriculture and Global Warming
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This document discusses the potential for organic agricultural systems to mitigate and adapt to climate change. Key points include: 1) Organic agriculture has potential to reduce greenhouse gas emissions through careful nutrient management and reduced nitrous oxide emissions from soils, as well as carbon sequestration in soils. 2) Estimates indicate organic agriculture could reduce agricultural greenhouse gas emissions by 20% through abstaining from mineral fertilizers and sequester carbon to compensate for 40-72% of current annual agricultural emissions. 3) Organic systems also have strong potential to build resilient food systems through diversification and building soil fertility, providing alternatives to energy-intensive inputs that may become limited due to rising energy prices.
Organic Agriculture and Global Warming
- 1. Renewable Agriculture and Food Systems: Page 1 of 12 doi:10.1017/S1742170510000116 Organic agriculture and climate change ¨ Nadia El-Hage Scialabba* and Maria Muller-Lindenlauf Natural Resources Management and Environment Department, Food and Agriculture Organization of the United Nations (FAO), Viale delle Terme di Caracalla, 00153 Rome, Italy. *Corresponding author: nadia.scialabba@fao.org Accepted 2 February 2010 Review Article Abstract This article discusses the mitigation and adaptation potential of organic agricultural systems along three main features: farming system design, cropland management and grassland and livestock management. An important potential contribution of organically managed systems to climate change mitigation is identified in the careful management of nutrients and, hence, the reduction of N2O emissions from soils. Another high mitigation potential of organic agriculture lies in carbon sequestration in soils. In a first estimate, the emission reduction potential by abstention from mineral fertilizers is calculated to be about 20% and the compensation potential by carbon sequestration to be about 40–72% of the world’s current annual agricultural greenhouse gas (GHG) emissions, but further research is needed to consolidate these numbers. On the adaptation side, organic agriculture systems have a strong potential for building resilient food systems in the face of uncertainties, through farm diversification and building soil fertility with organic matter. Additionally, organic agriculture offers alternatives to energy-intensive production inputs such as synthetic fertilizers which are likely to be further limited for poor rural populations by rising energy prices. In developing countries, organic agricultural systems achieve equal or even higher yields, as compared to the current conventional practices, which translate into a potentially important option for food security and sustainable livelihoods for the rural poor in times of climate change. Certified organic products cater for higher income options for farmers and, therefore, can serve as promoters for climate-friendly farming practices worldwide. Key words: organic agriculture, climate change, mitigation, adaptation, carbon sequestration, diversification, resilience Introduction emissions, the choice of food production practices can be a problem or a solution in addressing climate change. According to the Fourth Assessment Report of the Clearly, agriculture is highly dependent on climate Intergovernmental Panel on Climate Change (IPCC), green- conditions and is therefore subject to change and varia- house gas (GHG) emissions from the agricultural sector bility, with obvious impacts on food security. Changing account for 10–12% or 5.1–6.1 Gt of the total anthropo- environmental conditions such as rising temperatures, genic annual emissions of CO2-equivalents1. However, this changing precipitation patterns and an increase of extreme accounting includes only direct agricultural emissions; weather events seriously affect agricultural productivity, as emissions due to the production of agricultural inputs such vulnerability increases and even farming viability3. Until as nitrogen fertilizers, synthetic pesticides and fossil fuels 2030, adverse agricultural impacts are expected mainly in used for agricultural machinery and irrigation are not cal- tropical areas, where agriculture provides the primary culated. Furthermore, land changes in carbon stocks caused source of livelihood for more than 60% of the population in by some agricultural practices are not taken into account, sub-Saharan Africa4 and about 40–50% in Asia and the e.g., clearing of primary forests. Emissions by deforestation Pacific5. While a temperature rise of around 2 C is already due to land conversion to agriculture, which account for an inevitable1, agro-ecosystems designed to cope with stress additional 12%2 of the global GHG emissions, can be and adapt to change are strongly needed to facilitate food additionally allocated to agriculture. Thus, agriculture security and sustainable livelihoods in these regions. By production practices emit at least one-quarter of global 2050, all agroecosystems of the world—including those in anthropogenic GHG emissions and, if food handling and temperate areas—are expected to be affected by climate processing activities were to be accounted for, the total change1. Therefore, the quest for climate-proof food share of emissions from the agriculture and food sector systems is of interest to all. would be at least one-third of total emissions. Considering This article discusses the mitigation and adaptation the high contribution of agriculture to anthropogenic GHG potential of organic agricultural systems along three main # Cambridge University Press 2010
- 2. 2 ¨ N. El-Hage Scialabba and M. Muller-Lindenlauf features: farming system design, cropland management and fuel energy for machinery due to the use of mechanical grassland and livestock management. The objective is to weed control. A comparison of seven organic and draw a case where good agricultural management can com- conventional crops carried out in the UK showed a higher pensate today for most of the sector GHG emissions, while energy demand for machinery for all organic products. providing food and livelihoods. However, the higher energy demand for machinery did not outweigh the energy savings from foregoing synthetic Definition of Organic Agriculture fertilizers and pesticides14. The total energy use per product unit was lower for organic systems in all cases except for According to the Codex Alimentarius Commission, carrots, where a high energy demand for flame weeding ‘organic agriculture is a holistic production management was assumed. On average, the total energy demand for system that avoids use of synthetic fertilizers, pesticides and organic products was 15% lower14. genetically modified organisms, minimizes pollution of air, The reduced dependency on energy inputs in organic soil and water, and optimizes the health and productivity of agriculture reduces vulnerability to rising energy prices, interdependent communities of plants, animals and people’6. and hence volatility of agricultural input prices. Nitrogen To meet these objectives, organic agriculture farmers need fertilizer prices rose by 160% during the first quarter of to implement a series of practices that optimize nutrient and 200815, and price hikes are expected to recur with peak oil energy flows and minimize risk, such as crop rotations and and climate change, further limiting the access for poor enhanced crop diversity, different combinations of live- rural populations to agricultural inputs. Organic agriculture stock and plants, symbiotic nitrogen fixation with legumes, can be a promising approach to sustain food security by application of organic manure and biological pest control. supplying alternatives to agricultural inputs. All these strategies seek to make the best use of local An additional effect of the ban on nitrogen fertilizer resources. Hence, organic systems are inherently adapted to input is to give an incentive to enhance nutrient use site-specific endowments and limitations7,8. efficiency and therefore, reduce the risk of nitrous oxide In this article, we refer to all agricultural systems that emissions. Between 1960 and 2000, while agricultural pro- implement the practices described above, and not only to ductivity increased substantially with increased utilization systems that are certified as organic. Organic certification is of fertilizers, the global efficiency of nitrogen use for cereal required for market purposes, especially when distance is production decreased from 80 to 30%, while the risk of great from producers to consumers and there is a need to nitrogen emissions increased16. verify the organic claim. In developing countries, a huge Should all farming be managed organically, the current number of uncertified farms apply organic agriculture annual production of 100 megatons of nitrogen in mineral practices for their own subsistence purposes. It is to be fertilizers and the corresponding N2O emissions would fall highlighted that refraining from the use of synthetic inputs off; using an emission factor of 1.3% for the mineral does not qualify an operation as organic, as far as it is not fertilizer nitrogen, these emissions account for 10% of the accompanied by a proper farm design and management that anthropogenic GHG emissions from agriculture10,17. preserves natural resources from degradation. In 2007, Hence, the organic ban on the use of mineral fertilizers, certified organic lands were of 32 million hectares, in- reducing both energy demand for fertilizer manufacturing volving 1.2 million farmers9. and nitrous oxide emissions from fertilizer application, could lower the direct global agricultural GHG emissions Farming System Design by about 20%. Reduced use of synthetic fertilizers is believed to result Limited external inputs in lower yields per land unit, depending on the level of The use of external inputs is limited in organic farming intensity of the previous management system. A review systems. Synthetic inputs like mineral fertilizers and by Badgley et al.18 calculated average yield losses under chemical pesticides are banned. The energy used for the organic management for developed countries of 0–20% chemical synthesis of nitrogen fertilizers, which are totally and, in the case of developing countries, an increase of excluded in organic systems, represent up to 0.4–0.6 Gt yield or hardly any yield reduction. In low external input CO2 emissions10–12. This is as much as 10% of direct global systems, and especially in arid and semi-arid areas where agricultural emissions and around 1% of total anthro- most of the food-insecure live, organic yields generally pogenic GHG emissions. Williams et al. calculated the total improve up to 180%19,20. Higher yields in low-input primary energy burden of conventional wheat production in systems are mainly achieved by the application of manure the UK to be allocated by 56% to mineral fertilizers and by from integrated livestock production, composting and 11% to pesticides12. Pimentel calculated similar results for diversification. In humid areas, where traditionally less corn in USA, 30–40% for fertilization and 9–11% for plant livestock is integrated into the farming system and hence no protection for wheat and corn13. These emissions are livestock manure is available, organic yields depend on avoided by organic agriculture. the availability of other organic nitrogen sources. In paddy However, where labor is not available and conditions rice, nitrogen is supplied by nitrogen-fixing organisms allow it, organic management might require more fossil like Azolla21,22, with yields comparable to conventional
- 3. Organic agriculture and climate change 3 systems18. In perennial cropping, such as coffee or banana, harmonious balance between crop production and animal high yield reductions are more likely, even though in some husbandry. cases higher yields were measured18,23–27. However, in an A nutrient excess on the farm does not only lead to a high appropriate agroforestry system, lower yields for the main N2O emission risk but also to an inefficient use of the crop are compensated by producing other foodstuff and world’s limited resources. Where manure has to be trans- goods28,29. Agroforestry systems are encouraged by ported over great distance for application, high energy costs different standards for organic agriculture30–32. occur. On pastures, limited livestock density avoids over- Crop diversification grazing. Overgrazing is a risk factor for land degradation and leads to high soil carbon losses39–41. By abstaining from synthetic input use, organic agricultural The limitation of livestock units per hectare and the systems cannot but adapt to local environmental conditions. lower production intensity are incentives for multi-use Therefore, species and varieties are chosen for their livestock systems. Case study calculations showed that the adaptability to the local soil and climate and their resistance methane emissions from milk and beef production can be to local pests and diseases. Organic farmers prefer not to reduced more than 20% by keeping double-use breeds42 use uniform crops and breeds and opt for more robust tra- (i.e., for milk and meat production). Double-use breeds are ditional species, which they tend to conserve and develop. normally not kept in conventional systems because of their Additionally, growing different assemblages of crops in lower milk yields, but in roughage-based organic systems, time and space seeks to enhance the agro-ecosystem re- double-use breeds do not imply further yield losses and silience to external shocks such as extreme weather events hence are more likely to be used. or price variation33, which are all risks most likely to increase as the climate changes34. Diverse cropping systems in developing countries do not only rely on cash Maintenance and restoration of multi-functional crops but also on food crops for household consumption. landscapes Currently, most small-scale farmers are net buyers of food The integration of landscape features for the establishment and, thus, highly vulnerable to volatile food prices15. An of eco-functional landscapes is an important asset of independence from uniform commercial seeds and im- organic management. According to IFOAM, operators ported food increases self-reliance and promotes food shall take measures to maintain and improve landscape sovereignty. and enhance biodiversity30. This may include extensive The diversification of cropping systems also make more field margins, hedges, trees or bushes, woodlands, water- efficient use of available nutrients, with improved pro- ways, wetlands and extensive grasslands. ductivity and economic performance, which is of high The integration of landscape elements is mentioned as an importance in times of limited nutrients and financial effective mitigation strategy by the IPCC34, due to its constraints35. multiple adaptation effects. For example, hedges and trees are useful to reduce erosion, which is expected to be Integrated livestock production aggravated by climate change1. Reduced erosion goes along To be successful, organic agriculture must integrate plant with reduced losses of soil organic matter and, hence, in- and livestock production to the extent possible to optimize creased soil fertility. In organic systems, the water retention nutrient use and recycling. Currently, half of the world’s pork and drainage capacity of the ecosystem is enhanced and the production originates from industrial landless systems, and risk of floods or droughts is reduced. Meanwhile, carbon is for poultry meat this share amounts to over 70%.36 These sequestered in soil and plant biomass. While in conven- confined and intensive livestock systems lead to high nutrient tional systems, landscape elements are cleared because they excess on the farm level. For the USA, a comprehensive hinder mechanization and chemical control of pests and study carried out by the USDA in 1997 calculated a total weeds43, landscape elements in organic systems are farm-level excess of about 60% of the recoverable manure purposely created in order to provide habitats for wildlife nitrogen and 65% of the recoverable manure phosphorus37. that work synergistically with the cropping system; for Landless livestock production systems can rarely be example, predators keep pests under check and hedges found in organic agricultural systems. According to the protect from winds44,45. EU regulations on organic production, livestock units The adaptation effects of landscape features are particu- must not exceed 2 units per hectare, which is equivalent larly important in those areas where the strongest impacts to approximately 170 kg N38. Therefore, manure input is of climate change are expected. An analysis of climate risks tailored to plant uptake capacities, an aspect which is identified southern Africa and South Asia as the regions recommended as a mitigation strategy by the IPCC in where climate change will cause the most severe impacts order to reduce N2O emissions and leaching34. But, this for a large food-insecure human population46. The organic aspect of organic standards of other regions needs to be standards of these regions already include regulations further developed to meet the International Federation of concerning landscape elements. According to the East Organic Agricultural Movements (IFOAM) principle of a African Standard, trees shall be present and hedges should
- 4. 4 ¨ N. El-Hage Scialabba and M. Muller-Lindenlauf be encouraged31. The Pacific Organic Standard contains the instrument for achieving these aims is a diverse crop rotation, most specific climate-related standards, which requests including catch and cover crops and intercropping. properties over 5 ha to set aside a minimum of 5% of the certified area for wildlife, unless the property is following a traditional agroforestry or polyculture approach32. N2O emissions from soils Agroforestry systems have similar effects, even to a N2O emissions are the most important source of agricul- higher degree. They are recommended as mitigation tural emissions: 38% of agricultural GHG emissions34. The strategy by the IPCC34 and are encouraged by different IPCC attributes a default value of 1% to applied fertilizer standards for organic agriculture30–32. nitrogen as direct N2O emissions17. In other publications, emission factors of up to 3–5 kg N2O-N per 100 kg N-input Biomass burning and deforestation can be found52. These higher values for global N2O budget are due to the consideration of both direct and indirect CH4 and N2O from biomass burning account for 12% of the emissions, including also livestock production, NH3 and agricultural GHG emissions. Additionally, the carbon NO3 emissions, nitrogen leakage into rivers and coastal sequestered in the burned biomass is lost to the atmosphere. zones, etc. In organic agriculture, preparation of land by burning In organic systems, the nitrogen input to soils, and hence vegetation is restricted to a minimum30–32. the potential nitrous oxide emissions, are reduced. Mineral IFOAM organic standards ban the certification of fertilizers, which currently cause direct N2O emissions in primary ecosystems, which have recently been cleared or the range of 10% of agricultural GHG emissions, are totally altered31,32. Organic agriculture thus contributes to halting avoided (see the above section, ‘Limited external inputs’). deforestation resulting from forest conversion to croplands Catch and cover crops extract plant-available nitrogen (12% of global GHG emissions2) and thus highly con- unused by the preceding crop and keep it in the system. tributes to mitigating climate change. However, further Therefore, they further reduce the level of reactive nitrogen development of organic standards is needed. in the topsoil, which is the main driving factor for N2O emissions53,54. A study from The Netherlands comparing Restoration of degraded land 13 organically and conventionally managed farms showed Organic farming practices such as crop rotation, cover lower levels of soluble nitrogen in the organically managed crops, manuring and application of organic amendments are soils55. recommended strategies to restore degraded soils47 and N2O emissions show a very high variability over time hence improve the livelihoods of rural populations affected and are therefore difficult to determine56. The share of by climate change; 70% of the land in dry areas is assumed reactive nitrogen that is emitted as N2O depends on a to be degraded48. In the Tigray Province, one of the most broad range of soil and weather conditions and manage- degraded parts of Ethiopia, agricultural productivity was ment practices, which could partly foil the positive effect of doubled by soil fertility techniques over 1 million hectares lower nitrogen levels in topsoil. Effects of different soil con- through agroforestry, application of compost and intro- ditions are not yet well understood. Comparisons between duction of leguminous plants into the crop sequence49. By soils receiving manure versus mineral fertilizers found restoring soil fertility, yields were increased to a much higher N2O emissions after manure application compared greater extent at both farm and regional levels than by using to mineral fertilizer applications, but not for all soil purchased mineral fertilizers. types57,58. One study from Brittany found no significant Restoration of degraded land not only offers income differences between mineral and organic fertilization59. The opportunities for rural populations but also has a huge higher nitrous oxide emissions after incorporation of mitigation potential by increasing soil carbon sequestration. manure and plant residues are explained by the high The total mitigation potential by restoration of degraded oxygen consumption for decomposition of the organic land is estimated as 0.15 Gt (technical potential up to USD matter60–62. These peaks in N2O can be mitigated by 20 per t of carbon) and up to 0.7 Gt (physical potential)50. enhanced aeration of the top soil. In compacted soils, the As degraded lands usually host market-marginalized risk of nitrous oxide emissions is higher63,64. Organic man- populations, organic land management may be the only agement practices facilitate a lower bulk density, enhancing opportunity to improve food security through an organized soil aeration65,66. Low aeration is also a reason for partly use of local labor to rehabilitate degraded land and increase higher risk of N2O emissions in no-tillage systems67. productivity and soil carbon sequestration. The highest risk for N2O emissions in organic farms is the incorporation of legumes, which are the main nitrogen source for organic farms68. For Germany, emissions of Cropland Management 9 kg N2O ha - 1 were measured after incorporation of As nitrogen is far more limited in organic systems, there is a legumes. But the average of N2O emissions over the whole strong incentive to avoid losses and enhance soil fertility51. crop rotation was lower for the organic farm, as compared Furthermore, there is a need to reduce the risk of pest to the conventional system (4 kg N2O per hectare for the and diseases by preventive measures. The most important organic and 5 kg for the conventional system)69.
- 5. Organic agriculture and climate change 5 To sum up, while there are some indicators for higher between carbon sequestration and N2O. Conventional no- N2O emissions per kg nitrogen applied, there is no clear tillage systems perform well in terms of carbon seques- evidence for higher emission factors in organic systems. tration but can increase N2O emissions79–82. Although not Regarding the lower fertilization intensity and the higher yet well analyzed, in some cases no-tillage can lead to nitrogen use efficiency in low-input systems, both leading much higher N2O emissions67. For developing countries, to lower concentrations of reactive nitrogen in top soils, a there are still few research data available concerning soil lower overall risk of N2O emission from organic cultivated carbon sequestration rates and N2O emissions. soils can be assumed. However, as there is high uncertainty In the long term, the removal of GHGs from the in N2O emission factors, further research is recommended. atmosphere through soil carbon sequestration is limited. The level of soil organic matter does not increase indefinitely in any soil, but reaches a certain equilibrium, Carbon sequestration in cropland and depending on the soil and climatic conditions and manage- soil organic matter ment practices83. Lal estimates the carbon sink capacity of A second mitigation effect of cash and cover crops, the world’s agricultural soils by enhanced management intercropping and manure is an increased carbon sequestra- practices to be 21–51 Gt carbon, which is equivalent to all tion in the soil34,70,71. Several field studies have proved the anthropogenic GHG emissions over 2–3 years, referring to positive effect of organic farming practice on soil carbon 2004 emissions84. Thus, carbon sequestration in soils is not pools72–74. In Switzerland, a long-term trial biodynamic sufficient to achieve a climate neutral agriculture in the system showed a stable carbon content, while a carbon loss long run, but in the medium term, it can compensate of 15% in 21 years was measured for the compared con- inevitable agricultural emissions until more neutral produc- ventional system. In the USA, a field trial showed a fivefold tion practices are developed and widely used. higher carbon sequestration in the organic system (i.e., Additionally, it must be considered that carbon seques- 1218 kg of carbon per hectare per year) in comparison tration has a mitigation effect only if the sequestration is with conventional management74,75. The potential of permanent. There are scientific results showing that the carbon sequestration rate by organic farming for European carbon stored by no-tillage systems is released by a single agricultural soils has been estimated at 0–0.5 t C per hectare ploughing, presumably because of its labile quality85. per year71. Most of the soil-sequestered carbon is stored as soil Niggli et al.76 calculated the sequestration potential of organic matter84. In different long-term field trials, or- organic croplands to be 0.9–2.4 Gt CO2 per year (which ganic matter content in organically managed soils was is equivalent to an average sequestration potential of about higher86–88. Soil organic matter has positive effects on the 0.2–0.4 t C per hectare and year for all croplands), which water-capturing capacity of the soil. A higher water- represents 15–47% of total annual agricultural GHG capturing capacity strengthens the resilience to droughts emissions10,34,76. and reduces the risk of floods89, which are both more likely But some practices currently discussed for their high to increase with climate change. The need for irrigation is sequestration potential, such as no-tillage, are so far poorly lowered, which has an additional adaptation and mitigation applicable in organic systems. No-tillage is difficult in effect90. Furthermore, soil organic matter enhances the organic agricultural systems because the accompanied nutrient buffer capacity and the microbial activity, both insurgence of weeds cannot be faced with herbicides, as strengthening soil fertility. in conventional systems, but only by mechanical weed control, if affordable77. The estimated technical potential Paddy production carbon sequestration rate of conventional zero-tillage is 0.4 t C per hectare per year for Europe, which is slightly Another agricultural GHG source influenced by cropping higher than the sequestration potential of organic farming systems is methane from paddy rice fields, which accounts practices. However, Freibauer et al. argued that the for 11% of the global agricultural GHG emissions. The realistically achievable mitigation potential for organic main influencing factors are cultivars, organic amendments agriculture is higher (i.e., 3.8 Gt as compared to less than and drainage91. While organic amendments increase 2.5 Gt for the European Union) due to price premium emissions, drainage reduces emissions92. Organic systems incentives in organic management71. Furthermore, recent add more organic amendments but adding amendments in studies question the sequestration potential of no-tillage times of drainage could avoid higher emissions93,94. As systems. A review carried out in 2007 found no positive organic systems do not use herbicides, aquatic weeds tend effect of no-tillage on the total soil carbon stock when to be present in organic rice paddies—and weeds have an samples are taken deeper than 30 cm78. One study found additional decreasing effect on methane emissions95. The even higher concentrations of combustible C and N in yields in organic and conventional rice production do not the topsoil of organic systems, as compared to no-till differ significantly18,96,97. Generally, there are adverse ef- systems77. fects of organic paddy production on methane emissions One important factor to consider in assessing soil due to organic fertilization, while emission compensation management impact on GHG emissions is the trade-off measures (such as drainage) are not mandatory. Further
- 6. 6 ¨ N. El-Hage Scialabba and M. Muller-Lindenlauf research is needed to quantify and recommend organic are attempted (to different degrees) everywhere in organic practices conducive to climate mitigation. One promising livestock systems, there is an increasing awareness of the approach could be the combination of organic practices need to optimize the productivity of roughage with more with resource-saving systems as the ‘system of rice research and development. intensification’ (SRI), where soils are kept un-flooded most Methane emissions from organic livestock systems can of the growing period and hence methane emissions are be reduced by about 10% (under European conditions) significantly reduced98–100. through reduced animal replacement rates104, as a low replacement rate is more likely in systems with lower performance per cow since these are not pushed beyond Pasture, Livestock and Manure their limit. Also, stress resistance (an important factor under Management climate change conditions) and longevity are among the most important traits of organic breeding105. Methane emissions from enteric fermentation One of the most important sources of GHG emissions Manure management from agriculture are the methane emissions from enteric Methane and N2O from manure account for about 7% of the fermentation, which account for 4–5% of the global agricultural GHG emissions34. Methane emissions pre- anthropogenic GHG emissions1,34. The quantity of methane dominantly occur in liquid manure systems, while N2O emitted per product unit depends on the animal diet and the emissions are higher in solid manure systems and on cow breed’s performance. pastures34. There is a very high variance for both gaseous High milk yields per cow reduce emissions per product emissions, depending on composition, coverage, tempera- unit. High energy feedstuff (e.g., grains and soya) can ture and moisture of the manure. Measures leading to a reduce emissions because methane emissions mainly derive reduction of methane emissions from manure often increase from the digestion of fiber from roughage101. In developed emissions of N2O and vice versa106. Methane emissions countries, organic management usually achieves lower milk from liquid manure can be reduced nearly to zero by yields per cow than conventional production18; the main fermenting the slurry in biogas plants, which would have reason is a more roughage-based ration with low concen- the positive side effect of generating renewable energy and trate supply. However in developing countries, where two- is in line with organic principles. For N2O, there is limited thirds of the enteric methane emissions occur, organic mitigation potential for most animals worldwide34. systems achieve higher milk yields, as more careful management improves the relatively low performance of Carbon sequestration in grasslands traditional systems102. In organic systems, ruminants are kept to make Pastures are the favored feeding strategy for organic cattle. productive use of fodder legumes, which play an important Therefore, organic livestock management is an option for role as nitrogen source in organic crop rotations. Also, maintaining grasslands, which have a high carbon seques- many grasslands are not suitable for cropping due to tration potential34,107. Combined with a limited livestock topography, climate and soils, and the best productive use density to prevent overgrazing, organic grassland farming of these lands is to keep ruminants on them. High livestock could be a way to optimize carbon sequestration in performance is generally achieved by feeding high-energy grasslands108,109. crops, which neglects the unique ability of ruminants to The global carbon sequestration potential by improved digest roughage. Using crops for feed rather than food pasture management practices was calculated to be 0.22 t C poses substantial challenges to food security; currently, per ha per year110. Assuming 0.2 t C per ha per year for one-third of the world’s cropland is used to produce animal organic farming practices, the total carbon sequestration feed36, let alone all the inherent environmental problems potential of the world’s grassland would be 1.4 Gt per year that intensive cropping systems pose in terms of high N- at the current state, which is equivalent to about 25% of the fertilizer use, soil degradation and further land clearing. annual GHG emissions from agriculture10,34,76. Furthermore, high energy concentration in animal diets, if not managed very carefully, can lead to rumen acidification Organic Supply Chains and Lifestyle and secondary inflammations, which is a cause of animal illness103. Therefore, from an organic perspective, there are GHG emissions from energy use in the food chain are severe constrains to mitigating methane emissions from normally not counted as agricultural emissions. In inven- enteric fermentation by shifting to a high-energy diet by tory reports, they appear as emissions from energy supply, feeding higher amounts of concentrates. Organic principles industries and transport. There are no comprehensive data view livestock systems as part of a whole, including the available for the GHG emissions of the food sector on process through which feed is supplied. The objective of a global scale. In the USA, 19% of the fossil energy is used organic livestock management, though not yet achieved, is in the food sector13. A comparison of seven organic and to create a nearly closed nutrient cycle whereby feed is conventional crops in the UK showed a higher (n = 6) or the supplied on-farm. While integration and disintensification same (n = 1) energy demand for collection, transport and
- 7. Organic agriculture and climate change 7 Table 1. Mitigation potential of organic agriculture. Share of total Impacts of anthropogenic optimized organic Source of GHG GHG emissions management Remarks Direct emissions from 10–12% agriculture N2O from soils 4.2% Reduction Higher nitrogen use efficiency CH4 from enteric 3.5% Opposed effects Increased by lower performance and fermentation lower energy concentration in the diet but reduced by lower replacement rate and multi-use breeds Biomass burning 1.3% Reduction Burning avoided according to organic standards Paddy rice 1.2% Opposed effects Increased by organic amendments but lowered by drainage and aquatic weeds Manure handling 0.8% Equal Reduced methane emissions but no effect on N2O emissions Direct emissions from forest 12% Reduction Clearing of primary ecosystems restricted clearing for agriculture Indirect emissions Mineral fertilizers 1% Totally avoided Prohibited use of mineral fertilizers Food chain ? (Reduction) Inherent energy saving but still inefficient distribution systems Carbon sequestration Arable lands Enhanced Increased soil organic matter Grasslands Enhanced Increased soil organic matter distribution of organic products. The disadvantage of the for agroforestry in temperate Europe and comply with the organic products is due to the still small economy of scale organic aim of diversified multifunctional landscapes. of organic agriculture (i.e., 2% of global food retail9), Global food trade is energy efficient only when a leading to lower energy efficiency of collection and production process is energy competitive as compared to distribution. This disadvantage could be compensated by local production, either due to favorable climate (e.g., supplying products to local wholesalers and food shops14, coffee or bananas are best produced in tropical countries) or as well as by direct supply to consumers (e.g., box seasonality (e.g., vegetables). Transportation means (air, schemes) and by larger economies of scale. sea or road) is another determining factor in calculating Additionally, organic standards tend to support low- the carbon footprint of a traded product. Regional pro- energy technologies for packaging. IFOAM standards duction does not offer advantages when heating is needed. already cover packaging by advising processors of organic The Swiss organic standard already includes a strict limi- food to avoid unnecessary packaging materials and to use tation for greenhouse heating and air shipping of organic reusable, recycled, recyclable or biodegradable packaging, food112. whenever possible. This includes an intrinsic potential for Despite the trend of the past decade of conventional- energy saving. ization of organic food systems, including highly processed Certified organic agriculture is linked to consumption and functional foods, sophisticated packaging and global patterns that seek locally adapted, healthy and ecologically retailing, organic consumers are currently reverting to less friendly foods and goods. From a consumer’s point of view, energy demanding and decreased carbon footprint com- the organic philosophy of adaptation to local conditions modities. Currently, the organic community is developing involves a preference for seasonal and local food. A recent adequate carbon labels to be included within the organic study from Germany has shown that both seasonal and standards and labels113. regional consumption has remarkable effects on energy saving111. For example, for apples, a threefold higher en- ergy demand was calculated for intercontinental selling Conclusions (i.e., from New Zealand to Germany), as compared to Organic agricultural systems have an inherent potential to an average German production system that involves both reduce GHG emissions and to enhance carbon 6 months of cold storage (i.e., 5.1 MJ kg - 1, as compared sequestration in the soil (Table 1). to 1.6 MJ kg - 1). Apples produced in traditional orchard An important potential contribution of organically meadows showed the lowest total energy demand (i.e., managed systems is the careful management of nutrients, 0.6 MJ kg - 1). Orchard meadows can be seen as an example and hence the reduction of N2O emissions from soils,
- 8. 8 ¨ N. El-Hage Scialabba and M. Muller-Lindenlauf Table 2. Adaptation potential of organic agriculture. Objectives Means Impacts Alternative to industrial production Improvement of natural resources Reliance on local resources and independence inputs (i.e., mineral fertilizers processes and environmental from volatile prices of agricultural inputs and agrochemicals) to decrease services (e.g., soil formation, (e.g., mineral fertilizers) that accompany pollution predation) fossil fuel hikes In situ conservation and development Farm diversification (e.g., polycropping, Risk splitting (e.g., pests and diseases), of agrobiodiversity agroforestry and integrated enhanced use of nutrient and energy crop/livestock) and use of local flows, resilience to climate variability and varieties and breeds savings on capital-intensive seeds and breeds Landscaping Creation of micro-habitats (e.g., hedges), Enhanced ecosystem balance (e.g., pest permanent vegetative cover and prevention), protection of wild biodiversity wildlife corridors and better resistance to wind and heat waves Soil fertility Nutrient management (e.g., rotations, Increased yields, enhanced soil water coralling, cover crops and retention/drainage (better response to manuring) droughts and floods), decreased irrigation needs and avoided land degradation which are the most relevant single source of direct GHG mitigation potential in tropical and subtropical areas and emissions from agriculture. More research is needed to under the predominant management practices of developing quantify and improve the effects of organic paddy rice countries. production and to develop strategies to reduce methane More importantly, the adaptation aspects of organic emissions from enteric fermentation (e.g., by promoting agricultural practices must be the focus of public policies double-use breeds). Indirect GHG emissions are reduced in and research. One of the main effects of climate change is organic systems by avoidance of mineral fertilizers. an increase of uncertainties, both for weather events and With the current organic consumers’ demand, further global food markets. Organic agriculture has a strong emission reductions are expected when organic standards potential for building resilience in the face of climate include specific climate standards that consider, inter alia, variability (Table 2). reduced energy consumption in the organic food chain The total abstention from synthetic inputs in organic (e.g., limitations on greenhouse heating/cooling, processing agriculture has been a strong incentive to develop and packaging, food miles combined with life cycle agricultural management practices that optimize the natural assessment). The advantage of organic systems is that they production potential of specific agro-ecosystems, based on are driven by aware consumers and that they already carry a traditional knowledge and modern research. These strat- guarantee system of verification and labeling which is egies can be used to enhance agricultural communities that consonant with climate labeling113. have no access to purchased inputs, which is the case of the The highest mitigation potential of organic agriculture majority of the rural poor. The main organic strategies are lies in carbon sequestration in soils and in reduced clearing diversification and an increase of soil organic matter, of primary ecosystems. The total amount of mitigation is which both could enhance resilience against extreme difficult to quantify, because it is highly dependent on weather events and are recommended by the IPCC. These local environmental conditions and management practices. strategies have, in particular, a high potential to enhance the Should all agricultural systems be managed organically, productivity of degraded soils, especially in marginal areas, the omission of mineral fertilizer production and appli- while enhancing soil carbon sequestration. The adaptive cation is estimated to reduce the agricultural GHG approach inherent to organic agriculture offers simulta- emissions by about 20% — 10% caused by reduced N2O neous climate mitigation benefits. emissions and about 10% by lower energy demand. These Finally, certified organic products cater for higher avoided emissions are supplemented by an emission income options for producers and hence a market-based compensation potential through carbon sequestration in incentive for environmental stewardship. The scaling-up of croplands and grasslands of about 40–72% of the current organic agriculture would promote and support climate- annual agricultural GHG emissions76. However, further friendly farming practices worldwide. However, invest- research is needed to confirm these figures, as long-term ments in research and development of organic agriculture scientific studies are limited and do not apply to different are needed to better unlock its potential and application on kinds of soils, climates and practices. To date, most of the a large scale. research on the mitigation potential of agricultural practices has been carried out in developed countries; dedicated Acknowledgements. We thank Darko Znaor and Peter Melchett investigations are needed to assess and understand the for their helpful comments.
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