The state of sustainable agriculture and agroecology research and impacts: A survey of U.S. scientists

A growing body of research suggests that although sustainable agriculture, particularly agroecology, can address challenges such as those related to climate change, ecosystem services, food insecurity, and farmer livelihoods, the transition to such systems remains limited. To gain insight into the state of U.S. sustainable agriculture and agroecology, we developed a 28-question mixed-method survey that was administered to scientists in these fields. Respondents (N=168) represented diverse locations, institutions, and career stages. They offered varied definitions of sustainable agriculture, with 40% considering economic and social well-being to be core components. Respondents identified the amount and duration of public research funding as important obstacles to conducting research on sus- tainable agriculture (85% and 61%, respectively). Further, most expressed challenges in communi- cating findings beyond academia, including to the media and policymakers, potentially limiting the impacts of such research. However, respondents expressed satisfaction in several areas, including relationships with community members (81%) and local producers (81%), and interest from students (80%) and research communities (73%), suggesting positive momentum in this field. Earlier versus later career scientists rated research on “human dimensions” as more important, expressed greater concerns over career stability, and were less satisfied with opportunities for policy engagement. Results imply that greater public investments, particularly fostering human dimensions, could support a transition to agroecology and its associated benefits

Leveraging agroecology for solutions in food, energy, and water

Global agriculture is facing growing challenges at the nexus of interconnected food, energy and water systems, including but not limited to persistent food insecurity and diet-related diseases; growing demands for energy and consequences for climate change; and declining water resources, water pollution, floods and droughts. Further, soil degradation and biodiversity loss are both triggers for and consequences of these problems. In this commentary, we argue that expanding agroecological principles, tools, and technologies and enhancing biological diversity can address these challenges and achieve better socioeconomic outcomes. Agroecology is often described as multi- or transdiscplinary, and applies ecological principles to the design and management of agricultural systems through scientific research, practice and collective action. While agroecology has roots in the study of food systems, agricultural land use has many direct and indirect linkages to water and energy systems that could benefit from agroecological insights, including use of water resources and the development of bio-based energy products. Although opportunities from the science and the practice of agroecology transcend national boundaries, obstacles to widespread adoption vary. In this article, we therefore focus on the United States, where key barriers include a shortage of research funds, limited supporting infrastructure, and cultural obstacles. Nevertheless, simply scaling up current models of agricultural production and land use practices will not solve many of the issues specific to food related challenges nor would such an approach address related energy and water concerns. We conclude that a first critical step to discovering solutions at the food, energy, water nexus will be to move past yield as a sole measure of success in agricultural systems, and call for more holistic considerations of the co-benefits and tradeoffs of different agricultural management options, particularly as they relate to environmental and equity outcomes

Farmworkers at Risk

The estimated 2.4 million farmworkers in the United States are vital to US food production. However, these workers are exploited, undervalued, and vulnerable to compounding climate change threats. The Union of Concerned Scientists (UCS) assessed how pesticide exposure and heat stress conditions combine to present significant risks to farmworkers' health and safety. We focused on California, Florida, and Washington—states that lead the nation in pesticide use, farmworkers, and production of labor-intensive fruits, nuts, and vegetables. We found that farmworkers in these states already experience substantial threats and that these are likely escalating. Policies to protect farmworkers' well-being from the dangerous consequences of extreme heat and pesticides are urgently needed

Managing grazing lands to improve soils and promote climate change adaptation and mitigation: A global synthesis

The potential to improve soils to help farmers and ranchers adapt to and mitigate climate change has generated significant enthusiasm. Within this discussion, grasslands have surfaced as being particularly important, due to their geographic range, their capacity to store substantial quantities of carbon relative to cultivated croplands and their potential role in mitigating droughts and floods. However, leveraging grasslands for climate change mitigation and adaptation will require a better understanding of how farmers and ranchers who rely on them for their livelihoods can improve management and related outcomes. To investigate opportunities for such improvements, we conducted a meta-analysis of field experiments that investigated how soil water infiltration rates are affected by a range of management options: adding complexity to grazing patterns, reducing stocking rates or extended rest from grazing. Further, to explore the relationships between observed changes in soil water infiltration and soil carbon, we identified papers that reported data on both metrics. We found that in 81.9% of all cases, responses of infiltration rates to identified management treatments (response ratios) were above zero, with infiltration rates increasing by 59.3 ± 7.3%. Mean response ratios from unique management categories were not significantly different, although the effect of extended rest (67.9 ± 8.5%, n = 140 from 31 experiments) was slightly higher than from reducing stocking rates (42.0 ± 10.8%; n = 63 from 17 experiments) or adding complexity (34.0 ± 14.1%, n = 17 from 11 experiments).We did not find a significant effect of several other variables, including treatment duration, mean annual precipitation or soil texture; however, analysis of aridity indices suggested that grazing management may have a slightly larger effect in more humid environments. Within our database, we found that 42% of complexity studies, 41% of stocking rate studies and 29% of extended rest studies also reported at least some measure of soil carbon. Within the subset of cases where both infiltration rates and carbon were reported, response ratios were largely positive for both variables (at least 64% of cases had positive mean response ratios in all management categories). Overall, our findings reveal that a variety of management strategies have the potential to improve soil water infiltration rates, with possible benefits for soil carbon as well. However, we identified a shortage of well-replicated and detailed experiments in all grazing management categories, and call for additional research of both soil water and soil carbon properties for these critical agroecosystems. Includes supplemental materials

Comparing infiltration rates in soils managed with conventional and alternative farming methods: A meta-analysis

Identifying agricultural practices that enhance water cycling is critical, particularly with increased rainfall variability and greater risks of droughts and floods. Soil infiltration rates offer useful insights to water cycling in farming systems because they affect both yields (through soil water availability) and other ecosystem outcomes (such as pollution and flooding from runoff). For example, conventional agricultural practices that leave soils bare and vulnerable to degradation are believed to limit the capacity of soils to quickly absorb and retain water needed for crop growth. Further, it is widely assumed that farming methods such as no-till and cover crops can improve infiltration rates. Despite interest in the impacts of agricultural practices on infiltration rates, this effect has not been systematically quantified across a range of practices. To evaluate how conventional practices affect infiltration rates relative to select alternative practices (no-till, cover crops, crop rotation, introducing perennials, crop and livestock systems), we performed a meta-analysis that included 89 studies with field trials comparing at least one such alternative practice to conventional management. We found that introducing perennials (grasses, agroforestry, managed forestry) or cover crops led to the largest increases in infiltration rates (mean responses of 59.2 ± 20.9% and 34.8 ± 7.7%, respectively). Also, although the overall effect of no-till was non-significant (5.7 ± 9.7%), the practice led to increases in wetter climates and when combined with residue retention. The effect of crop rotation on infiltration rate was non-significant (18.5 ± 13.2%), and studies evaluating impacts of grazing on croplands indicated that this practice reduced infiltration rates (-21.3 ± 14.9%). Findings suggest that practices promoting ground cover and continuous roots, both of which improve soil structure, were most effective at increasing infiltration rates

Seasonal Evapotranspiration Patterns in Mangrove Forests

Diurnal and seasonal controls on water vapor fluxes were investigated in a subtropical mangrove forest in Everglades National Park, Florida. Energy partitioning between sensible and latent heat fluxes was highly variable during the 2004–2005 study period. During the dry season, the mangrove forest behaved akin to a semiarid ecosystem as most of the available energy was partitioned into sensible heat, which gave Bowen ratio values exceeding 1.0 and minimum latent heat fluxes of 5 MJ d1. In contrast, during the wet season the mangrove forest acted as a well-watered, broadleaved deciduous forest, with Bowen ratio values of 0.25 and latent heat fluxes reaching 18 MJ d1. During the dry season, high salinity levels (\u3e30 parts per thousand, ppt) caused evapotranspiration to decline and correspondingly resulted in reduced canopy conductance. From multiple linear regression, daily average canopy conductance to water vapor declined with increasing salinity,vapor pressure deficit, and daily sums of solar irradiance but increased with air temperature and friction velocity. Using these relationships, appropriately modified Penman-Monteith and Priestley-Taylor models reliably reproduced seasonal trends in daily evapotranspiration. Such numerical models, using site-specific parameters, are crucial for constructing seasonal water budgets, constraining hydrological models, and driving regional climate models over mangrove forests

The state of sustainable agriculture and agroecology research and impacts: A survey of U.S. scientists

A growing body of research suggests that although sustainable agriculture, particularly agroecology, can address challenges such as those related to climate change, ecosystem services, food insecurity, and farmer livelihoods, the transition to such systems remains limited. To gain insight into the state of U.S. sustainable agriculture and agroecology, we developed a 28-question mixed-method survey that was administered to scientists in these fields. Respondents (N=168) represented diverse locations, institutions, and career stages. They offered varied definitions of sustainable agriculture, with 40% considering economic and social well-being to be core components. Respondents identified the amount and duration of public research funding as important obstacles to conducting research on sus- tainable agriculture (85% and 61%, respectively). Further, most expressed challenges in communi- cating findings beyond academia, including to the media and policymakers, potentially limiting the impacts of such research. However, respondents expressed satisfaction in several areas, including relationships with community members (81%) and local producers (81%), and interest from students (80%) and research communities (73%), suggesting positive momentum in this field. Earlier versus later career scientists rated research on “human dimensions” as more important, expressed greater concerns over career stability, and were less satisfied with opportunities for policy engagement. Results imply that greater public investments, particularly fostering human dimensions, could support a transition to agroecology and its associated benefits

Summertime Influences of Tidal Energy Advection on the Surface Energy Balance in a Mangrove Forest

Mangrove forests are ecosystems susceptible to changing water levels and temperatures due to climate change as well as perturbations resulting from tropical storms. Numerical models can be used to project mangrove forest responses to regional and global environmental changes, and the reliability of these models depends on surface energy balance closure. However, for tidal ecosystems, the surface energy balance is complex because the energy transport associated with tidal activity remains poorly understood. This study aimed to quantify impacts of tidal flows on energy dynamics within a mangrove ecosystem. To address the research objective, an intensive 10-day study was conducted in a mangrove forest located along the Shark River in the Everglades National Park, FL, USA. Forest–atmosphere turbulent exchanges of energy were quantified with an eddy covariance system installed on a 30-m-tall flux tower. Energy transport associated with tidal activity was calculated based on a coupled mass and energy balance approach. The mass balance included tidal flows and accumulation of water on the forest floor. The energy balance included temporal changes in enthalpy, resulting from tidal flows and temperature changes in the water column. By serving as a net sink or a source of available energy, flood waters reduced the impact of high radiational loads on the mangrove forest. Also, the regression slope of available energy versus sink terms increased from 0.730 to 0.754 and from 0.798 to 0.857, including total enthalpy change in the water column in the surface energy balance for 30-min periods and daily daytime sums, respectively. Results indicated that tidal inundation provides an important mechanism for heat removal and that tidal exchange should be considered in surface energy budgets of coastal ecosystems. Results also demonstrated the importance of including tidal energy advection in mangrove biophysical models that are used for predicting ecosystem response to changing climate and regional freshwater management practices