Is Plant Phenology Keeping Pace with the Climate?

Changes in plant phenology, the seasonal timing of life history events, is one of the most visible fingerprints of climate change impacts. Numerous studies document the phenological shifts in response to climate change but disagree on the rate and extent of responses by species, area, and time. A potential mismatch between phenology and climate may reduce plant fitness and lead to changes in species distribution, community composition, and ecosystem processes. Using a common metric of "velocity of change" (i.e., the speed and direction of isoline movement), we conducted a systematic evaluation of how plant phenological shifts keep pace with climate change in northern mid- to high- latitudes (30°N-70°N) over three decades (1981-2014). Using satellite-derived phenology data and station-based temperature data, the velocity of phenology change (10.1 km/year) was calculated to almost double the velocity of climate change (4.9 km/year), but the inconsistencies in directions resulted in a net mismatch between the two velocities (2.1 km/year). The velocities and mismatches differ by land cover type, with land covers modified by human activities (settlements, croplands, rangelands, and seminatural woodlands) having greater mismatches compared to the wildlands. The mismatch was also found to increase with the degree of urbanization, evaluated by the nighttime stable lights. Overall, we found a widespread mismatch between phenological shift and climate change with high spatial heterogeneity, which was exacerbated by anthropogenic land uses. By studying the spatial pattern of phenological response to climate change and identifying areas with high risks of phenological mismatch, we can improve our ability to cope with challenges in a changing environment.