The Paris Climate Agreement represents an ambitious goal to reduce greenhouse gas (GHG) emissions to limit global climate warming to between 1.5 and 2.0 degrees Celsius (°C). Although the focus is on reduction of fossil-fuel emissions, improved land-management practices offer a crucial opportunity to contribute to this goal while also providing other important cobenefits, including provision of clean water, reduction in air pollution, and maintenance of biodiversity. A recent global analysis found that 20 cost-effective pathways of conservation, restoration, and improved land-management practices could reduce emissions by 11.3 petagrams of carbon dioxide equivalent (PgCO2e) per year, representing 37 percent of the Paris Agreement goal by the year 2030 (Griscom et al. 2017). This analysis also found that 4.1 PgCO2e per year of this emission reduction was low cost ($10 per megagram of carbon dioxide equivalent or less). This letter focuses on these low-cost opportunities because it is critically important to implement them as soon as possible, recognizing that more costly or complex solutions may take longer to implement. The low-cost emission-reduction potential is dominated by forest- and tree-related pathways, including avoided forest conversion and natural forest management (55 percent of total low-cost potential). However, cropland nutrient management is the second-largest low-cost pathway, indicating an important role for agriculture in mitigating climate change at low cost. Combined, agricultural practices account for 26 percent of the low-cost potential (1.1 PgCO2e per year, including cropland nutrient management, conservation agriculture, legumes in pastures, improved rice cultivation, and optimized grazing intensity). The remaining potential (19 percent) is from wetland-dominated pathways, including avoided peatland impacts, peatland restoration, and avoided coastal wetland impacts. In addition, many of the nonagricultural pathways interact in important ways with agriculture; therefore, it is critically important to recognize and deploy these interactive pathways in concert. Notably, some important low-cost forest pathways depend largely on the intensification of agricultural pathways (increased food yield per hectare), as well as human dietary changes, such as reducing beef consumption. For example, the pathway with the greatest low-cost GHG mitigation is avoided forest conversion, which depends on the sustainable intensification of existing agricultural land because 54 percent of forestland conversion is to commercial agriculture (Hosonuma et al. 2012). Similarly, some of the wetland pathways interact in important ways with agriculture. For example, avoided peatland conversion depends in part on producing crops such as oil palm on nonpeatlands. For all of these reasons, agriculture has a dominant role to play in these interacting natural climate solution pathways, particularly the low-cost opportunities. However, agricultural mitigation must occur without compromising food security (Stefan et al. 2017). One reason for the low cost of some agricultural GHG mitigation opportunities is that they can increase yields, decrease costs, or both. For example, nitrogen (N) fertilizer can be used more efficiently with the correct formulation, timing, placement, and rate, reducing costs while maintaining or increasing yields (Davidson et al. 2015, Kanter et al. 2015, McLellan et al. 2018). In the United States, on-farm testing showed that modern Web-based tools for N management in maize could decrease annual N application rate by 34 percent by means of improved spatial and temporal precision and adaptive in-season applications rates. These improvements occur while maintaining yields and improving profitability by $65 per hectare (Sela et al. 2016, 2018). Furthermore, reduced N fertilizer application also reduces GHG emissions that occur upstream during fertilizer manufacture. In addition, in some countries such as China, subsidies for N fertilizer encourage overuse, indicating a large opportunity to reduce N rate while maintaining yields (Zhang et al. 2015, Kanter et al. 2015). Recent research has suggested that GHG emissions from agriculture, forestry, and land-use change have been underestimated (Mahowald et al. 2017); therefore, agricultural opportunities for GHG mitigation may be even more critical to achieving the goals of the Paris Agreement while making agriculture more sustainable and providing other ecosystem services. However, attention and funding for GHG mitigation have not focused on land-management opportunities. I suggest that more emphasis be placed on implementing improved land-management practices to reduce GHG emissions, beginning with the low-cost opportunities. Agriculture, including interacting agricultural and forest pathways, can provide most of this low-cost GHG mitigation while also providing the cobenefits of clean water, reduction in air pollution, and maintenance of biodiversity. The time is now to implement these opportunities. References cited Davidson EA , Suddick EC , Rice CW , Prokopy LS . 2015 . More food, low pollution (Mo Fo Lo Po): A grand challenge for the 21st century . Journal of Environmental Quality 44 : 305 – 311 . Google Scholar CrossRef Search ADS PubMed Griscom BW et al. 2017 . Natural climate solutions . Proceedings of the National Academy of Sciences 114 : 11645 – 11650 . Google Scholar CrossRef Search ADS Hosonuma N , Herold M , de Sy V , de Fries RS , Brockhaus M , Verchot L , Angelsen A , Romijn E . 2012 . An assessment of deforestation and forest degradation drivers in developing countries . Environmental Research Letters 7 (art. 4009). Kanter DR , Zhang X , Mauzerall DL . 2015 . Reducing nitrogen pollution while decreasing farmers’ costs and increasing fertilizer industry profits . Journal of Environmental Quality 44 : 325 – 335 . Google Scholar CrossRef Search ADS PubMed Mahowald NM , Ward DS , Doney SC , Hess PG , Randerson JT . 2017 . Are the impacts of land use on warming underestimated in climate policy? Environmental Research Letters 12 (art. 094016). McLellan EL , Cassman KG , Eagle AJ , Woodbury PB , Sela S , Tonitto C , Marjerison D , van Es HM . 2018 . The nitrogen balancing act: Tracking the environmental performance of food production . Bioscience 68 : 194 – 203 . Google Scholar PubMed Sela S , van Es HM , Moebius-Clune BN , Marjerison R , Melkonian J , Moebius-Clune D , Schindelbeck R , Gomes S . 2016 . Adapt-N outperforms grower-selected nitrogen rates in Northeast and Midwestern United States strip trials . Agronomy Journal 108 : 1726 – 1734 . Google Scholar CrossRef Search ADS Sela S , Woodbury PB , van Es HM . 2018 . Dynamic model-based N management reduces surplus nitrogen and improves the environmental performance of corn production . Environmental Research Letters 13 (art. 054010). https://doi.org/10.1088/1748-9326/aab908 Stefan F et al. 2017 . Reducing greenhouse gas emissions in agriculture without compromising food security? Environmental Research Letters 12 (art. 105004). Zhang X , Davidson EA , Mauzerall DL , Searchinger TD , Dumas P , Shen Y . 2015 . Managing nitrogen for sustainable development . Nature 528 : 51 – 59 . Google Scholar PubMed © The Author(s) 2018. Published by Oxford University Press on behalf of the American Institute of Biological Sciences. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)
BioScience – Oxford University Press
Published: Jun 6, 2018
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