LAUSR

El Niño has profound influences on ecosystem dynamics. However, we know little about how it shapes vertebrate faunal community composition over centennial time scales, and this limits our ability to forecast change under projections of future El Niño events. On the basis of correlations between geological records of past El Niño frequency and the species composition of bird and fish remains from a Baja California bone deposit that spans the past 12,000 years, we documented marked faunal restructuring when major El Niño events occurred more than five times per century. This tipping point has implications for the past and future ecology of eastern Pacific coastal environments. Description A faunal tipping point El Niño events occur in the eastern Pacific ocean when warm surface waters prevent normal upwelling of nutrient-rich, cooler water. These events are unpredictable but are increasing in frequency and intensity, likely due to climate change, and have impacts on marine and terrestrial environments, ocean currents, and climate. Broughton et al. looked across a 12,000-year record from a coastal site in Baja, California at the impacts of El Niño events as measured by changes in the fossil record (see the Perspective by Sandweiss and Maasch). They found that in centuries with five or more events, marine fauna decreased whereas terrestrial diversity increased, indicating a tipping point for these communities. —SNV When five or more strong El Niño events occur per century, coastal ecosystems undergo dramatic faunal turnover.