Tracing vegetation stress from space: isoprene emissions capture the spatiotemporal footprint of El Niño

Abstract El Niño events exert a profound influence on the global carbon cycle by imposing widespread heat and water stress on terrestrial ecosystems. Plant isoprene emissions respond rapidly to such stress, yet it remains unclear whether this response can track the spatiotemporal evolution of El Niño’s impacts over land. Here, we used satellite-derived global isoprene emissions for the first time to assess the west-east progression of the 2015–2016 El Niño. We observed that isoprene emissions increased by up to approximately 30% across tropical ecosystems relative to the climatological mean, with pronounced anomalies emerging during the event. The spatiotemporal evolution of these anomalies closely aligns with the El Niño progression inferred from sea surface temperature (SST) anomalies in the equatorial Pacific. In contrast, commonly used satellite vegetation products, including leaf area index (LAI) and solar-induced chlorophyll fluorescence (SIF), show weaker and spatially incoherent responses. These results demonstrate that satellite-derived isoprene provides a sensitive and mechanistically grounded tracer of ecosystem stress, offering a complementary perspective for monitoring the intensity and propagation of extreme climate events across terrestrial ecosystems.