Global carbon dioxide efflux from rivers enhanced by high nocturnal emissions

Carbon dioxide (CO2) emissions to the atmosphere from running waters are estimated to be four times greater than the total carbon (C) flux to the oceans. However, these fluxes remain poorly constrained because of substantial spatial and temporal variability in dissolved CO2 concentrations. Using a global compilation of high-frequency CO2 measurements, we demonstrate that nocturnal CO2 emissions are on average 27% (0.9 gC m−2 d−1) greater than those estimated from diurnal concentrations alone. Constraints on light availability due to canopy shading or water colour are the principal controls on observed diel (24 hour) variation, suggesting this nocturnal increase arises from daytime fixation of CO2 by photosynthesis. Because current global estimates of CO2 emissions to the atmosphere from running waters (0.65–1.8 PgC yr−1) rely primarily on discrete measurements of dissolved CO2 obtained during the day, they substantially underestimate the magnitude of this flux. Accounting for night-time CO2 emissions may elevate global estimates from running waters to the atmosphere by 0.20–0.55 PgC yr−1

Unpacking social-ecological transformations: Conceptual, ethical and methodological insights

Social-ecological systems contribute to environmental change and, in turn, face its corresponding shocks and disturbances. As scholarship on resilience and social-ecological transformations grows, researchers from various disciplines continue to debate how major transitions and environmental change can be anticipated, studied or guided towards just and ethical outcomes. To this end, we apply an interdisciplinary perspective to describing key aspects of social-ecological transformations scholarship around three pressing questions: (1) What features or criteria distinguish transformations from other forms of change?; (2) What are the political, ethical, and normative concerns associated with transformations?; and (3) How can we better track, measure, and evaluate such transformations? Our insights, which emerged from a workshop with early-career interdisciplinary scholars, highlight questions of justice, equity and ethics in transformations research, and suggest that more precise indicators of change, a more explicit understanding of system boundaries, and a dual focus on process and outcomes will help advance our understanding of the social-ecological implications of transformations. We hope that articulating these challenges and recommendations in an interdisciplinary framing will help further the conversation on these critical topics and provide an accessible perspective of key considerations for multidisciplinary scholarship on social-ecological transformations

The global divide in data-driven farming

Big data and mobile technology are widely claimed to be global disruptive forces in agriculture that benefit small-scale farm-ers. Yet the access of small-scale farmers to this technology is poorly understood. We show that only 24–37% of farms of 200 ha in size. Furthermore, croplands with severe yield gaps, climate-stressed locations and food-insecure populations have poor service coverage. Across many countries in Africa, less than ~40% of farming households have Internet access, and the cost of data remains prohibitive. We recommend a digital inclusion agenda whereby governments, the development community and the private sector focus their efforts to improve access so that data-driven agriculture is available to all farmers globally