Ecological lines of least resistance shape community responses to climate change

<title>Abstract</title> <p>Ecological communities worldwide are exposed to multiple dimensions of climate change, such as shifts in temperature and water availability, which impact species’ performance and alter community composition. Here we ask whether community composition tracks multidimensional climate change more closely in some directions than others. Across four climate variables and 11,279 forest plots re-censused at 10 years, community composition became increasingly mismatched with climate when the direction of climate change diverged from an ecological line of least resistance—the dominant axis of variation in species’ climatic niche optima. As the directional divergence increased from 3° to 90°, the predicted mismatch between climate and the community mean climatic optimum increased by the equivalent of 0.5 °C per decade. Communities may be vulnerable to climatic shifts in directions that are poorly matched with resident species’ niche optima—even if no individual climate variable reaches extreme values.</p>