Identification of Optimum Temperatures for Photosynthetic Production in Subtropical Coastal Ecosystems: Implications for CO₂ Sequestration in a Warming World

Abstract

Abstract Terrestrial ecosystems are often thought to be effective sinks of anthropogenic CO 2 emissions with biosphere greening considered unequivocal evidence of this process. Increasing atmospheric concentrations of CO 2 along with other greenhouse gases are however, responsible for global warming. As temperature increases, the rate at which biomes sequester CO 2 may decline as the optimum temperature for photosynthetic production is exceeded, thereby reducing their potential to sequester CO 2 . Here we present evidence from 3 years of direct measurements of CO 2 exchanges over subtropical coastal ecosystems in eastern Australia that the optimum temperature range for photosynthesis of 24.1°C to 27.4°C is routinely exceeded. This causes a rapid decline in photosynthetic production made worse when soil water content decreases. As climate change continues, both rising temperatures and predicted decline in rainfall will see these coastal ecosystems ability to sequester CO 2 decrease further rapidly. We suggest similar research is needed urgently over other terrestrial ecosystems.