Sean Smukler

Identifying potential synergies and trade-offs for meeting food security and climate change objectives in sub-Saharan Africa

Potential interactions between food production and climate mitigation are explored for two situations in sub-Saharan Africa, where deforestation and land degradation overlap with hunger and poverty. Three agriculture intensification scenarios for supplying nitrogen to increase crop production (mineral fertilizer, herbaceous legume cover crops—green manures—and agroforestry—legume improved tree fallows) are compared to baseline food production, land requirements to meet basic caloric requirements, and greenhouse gas emissions. At low population densities and high land availability, food security and climate mitigation goals are met with all intensification scenarios, resulting in surplus crop area for reforestation. In contrast, for high population density and small farm sizes, attaining food security and reducing greenhouse gas emissions require mineral fertilizers to make land available for reforestation; green manure or improved tree fallows do not provide sufficient increases in yields to permit reforestation. Tree fallows sequester significant carbon on cropland, but green manures result in net carbon dioxide equivalent emissions because of nitrogen additions. Although these results are encouraging, agricultural intensification in sub-Saharan Africa with mineral fertilizers, green manures, or improved tree fallows will remain low without policies that address access, costs, and lack of incentives. Carbon financing for small-holder agriculture could increase the likelihood of success of Reducing Emissions from Deforestation and Forest Degradation in Developing Countries programs and climate change mitigation but also promote food security in the region.

Community essay tools for enhancing interdisciplinary communication

Abstract This is a collaborative community essay, written by ten postdoctoral research fellows who had the opportunity to come together at Columbia University’s interdisciplinary Earth Institute. In many ways, we were different: our disciplinary backgrounds run the gamut in physical and social sciences; we study in different parts of the world, from sub-Saharan Africa to Latin America; we approach our work differently—some of us spend our days in the field collecting and analyzing soil samples, others conduct in-depth interviews in rural communities, while still others spend time in the lab elaborating formulas and crunching numbers. Yet, we found common ground: all of us are committed to addressing issues of sustainability in complex environments. As such, we wanted to harness our diversity and various strengths to bring together scientific, political, economic, demographic, geographic, ecological, and ethical perspectives on the challenges and opportunities of sustainable development. We remain ambitious in our aims. Nonetheless, we realized that our first task was figuring out how to communicate effectively across often disparate disciplines. This community essay chronicles that part of our journey. We hope it will be of use to others who endeavor to work across and beyond traditional academic disciplines.

Ecosystem Services in Agricultural Landscapes

There is a tenuous relationship between the world’s rural poor, their agriculture, and their surrounding environment. People reliant on farming for their livelihood can no longer focus on current food production without considering the ecosystem processes that ensure long-term production and provide other essential resources required for their well-being. Farmers are now expected to not only produce food, but also steward the landscape to ensure the provisioning of drinking water, wood products for construction and cooking, the availability of animal fodder, the capacity for flood attenuation, the continuity of pollination, and much more. Farmer stewardship of the landscape helps ensure ecological functions that, when beneficial to human well-being, are referred to as ecosystem services. Human activities strongly affect ecosystem services and there is often a resulting trade-off among their availability, which frequently results in the loss of many at the expense of few, most notably when producing food (Foley et al. 2005).

Effective monitoring of agriculture: a response

The development of effective agricultural monitoring networks is essential to track, anticipate and manage changes in the social, economic and environmental aspects of agriculture. We welcome the perspective of Lindenmayer and Likens (J. Environ. Monit., 2011, 13, 1559) as published in the Journal of Environmental Monitoring on our earlier paper, Monitoring the Worlds Agriculture (Sachs et al., Nature, 2010, 466, 558-560). In this response, we address their three main critiques labeled as the passive approach, the problem with uniform metrics and the problem with composite metrics. We expand on specific research questions at the core of the network design, on the distinction between key universal and site-specific metrics to detect change over time and across scales, and on the need for composite metrics in decision-making. We believe that simultaneously measuring indicators of the three pillars of sustainability (environmentally sound, social responsible and economically viable) in an effectively integrated monitoring system will ultimately allow scientists and land managers alike to find solutions to the most pressing problems facing global food security.

Predicting carbon benefits from climate-smart agriculture: High-resolution carbon mapping and uncertainty assessment in El Salvador

Agroforestry management in smallholder agriculture can provide climate change mitigation and adaptation benefits and has been promoted as climate-smart agriculture (CSA), yet has generally been left out of international and voluntary carbon (C) mitigation agreements. A key reason for this omission is the cost and uncertainty of monitoring C at the farm scale in heterogeneous smallholder landscapes. A largely overlooked alternative is to monitor C at more aggregated scales and develop C contracts with groups of land owners, community organizations or C aggregators working across entire landscapes (e.g., watersheds, communities, municipalities, etc.). In this study we use a 100-km2 agricultural area in El Salvador to demonstrate how high-spatial resolution optical satellite imagery can be used to map aboveground woody biomass (AGWB) C at the landscape scale with very low uncertainty (95% probability of a deviation of less than 1%). Uncertainty of AGWB-C estimates remained low (<5%) for areas as small as 250 ha, despite high uncertainties at the farm and plot scale (34-99%). We estimate that CSA adoption could more than double AGWB-C stocks on agricultural lands in the study area, and that utilizing AGWB-C maps to target denuded areas could increase C gains per unit area by 46%. The potential value of C credits under a plausible adoption scenario would range from

Monitoring the world's agriculture

38,270 to

Biodiversity and multiple ecosystem functions in an organic farmscape.

354,000 yr-1 for the study area, or about

Commonness and rarity of species: Does species’ rank influence contribution to ecosystem function?

13 to

Monitoring, reporting, and verification methodologies for agriculture, forestry, and other land use

124xa0ha-1xa0yr-1, depending on C prices. Considering farm sizes in smallholder landscapes rarely exceed 1-2xa0ha, relying solely on direct C payments to farmers may not lead to widespread CSA adoption, especially if farm-scale monitoring is required. Instead, landscape-scale approaches to C contracting, supported by satellite-based monitoring methods such as ours, could be a key strategy to reduce costs and uncertainty of C monitoring in heterogeneous smallholder landscapes, thereby incentivizing more widespread CSA adoption.