Thermodynamic Entropy Production as a Metric of Sustainability

The ability to quantify sustainability is essential to climate change research and has the potential to greatly influence decision-making. Thermodynamic entropy production calculated from eddy covariance (EC) tower data offers promise for quantifying the sustainability of different land cover types with varying levels of disturbance. Entropy production results from fluxes of heat, matter, and momentum and is related to the fluxes and gradients of temperatures and concentrations. Higher vegetative fraction corresponds to greater entropy production, which increases through ecological succession and is sustained at maturity until disturbance or retrogression. Energy inputs in agricultural systems lead to higher production of entropy relative to other ecosystems, and the greater the entropy production, the less sustainable the ecosystem. In this study, thermodynamic entropy production was computed for 77 AmeriFlux site years across croplands, forests, and grasslands in the US. Annual entropy production for all sites was compared to driving variables of temperature, precipitation, and soil moisture for different land cover types. Preliminary results show that the thermodynamic entropy production metric is a useful indicator of ecological succession from grasslands to forests and the higher entropy production associated with anthropogenic energy inputs in agricultural systems. Croplands exhibit intermediate levels of entropy production, between lower values of grasslands and higher values of forests. Within class variability amongst grassland, cropland, and forest sites is indicative of annual variation in driving variables and calls for an examination of site-specific land management practices and land use histories. Entropy production across all sites shows a strong relationship with carbon dynamics.