Insights into terrestrial carbon and water cycling from the global eddy covariance network

Ecosystem–atmosphere exchanges of carbon dioxide (CO2) and water vapour respond to global environmental changes, such as climate change, elevated atmospheric CO2, disturbances, and land use change and management. Understanding these exchanges requires globally distributed and continuous, long-term ecosystem-scale measurements spanning diverse climates and ecosystems, as supported by the development of the eddy covariance (EC) technique. In this Review, we discuss how the global network of EC sites, led by FLUXNET, has advanced understanding of terrestrial carbon and water cycling. Since the early 1990s, EC measurements have provided insights into variations in carbon and water fluxes across different timescales (half-hourly to decadal), vegetation types and environmental gradients, and their responses to global change. Upscaling EC measurements and the resulting datasets have also enhanced understanding of the magnitude, spatial patterns, seasonal changes, interannual variability, and trends in carbon sinks and sources, evapotranspiration, and water-use efficiency in response to global change at regional to global scales. EC measurements and upscaled data also help interpret and evaluate satellite-derived products, as well as benchmark and improve terrestrial biosphere models and Earth system models. Future efforts should improve network representativeness, foster open data sharing, provide near real-time measurements, enhance accuracy of upscaled products and better support climate mitigation efforts.