Changes in plant phenology, the seasonal timing of life history events, is one of the most visible fingerprints of climate change impacts. A potential mismatch between phenology and climate may reduce plant fitness and lead to changes in species distribution, community composition, and ecosystem processes. Despite numerous studies on warming-induced phenological shifts, it is unclear if these observed shifts match the pace of climate change. It is particularly unclear how phenology in human-dominated landscapes tracks the climate, given the significant influence of human activities on phenology. Using “velocity of change” (i.e., the speed and direction of isoline movement) as a common metric for both phenology and climate, we systematically quantified how shifts in remotely-sensed land surface phenology track temperature change in terms of speed and direction in northern mid- to high- latitudes (30°N–70°N) over the last three decades (1981–2014). We further examined how the pacing of phenology change relative to temperature change is associated with anthropogenic land uses across different land use types and a human population gradient.
Results/Conclusions
Our results indicate that the velocity of phenology change (5.4 km yr–1, 95% CI: 0.2–37.5 km yr–1) was almost double that of the velocity of temperature change (2.2 km yr–1, 95% CI: 0.2–15.1 km yr–1) in magnitude. The pacing of phenology change relative to temperature change was complicated by the inconsistencies in direction. In wildlands, the velocity of phenology change outpaced that of temperature change. In anthropogenic landscapes such as croplands, rangelands, and seminatural lands, however, the pacing of phenology change lagged behind. Further, we found this lag between phenology and temperature to be positively correlated with human population density, with a 1% increase in population density corresponding to a 0.69 km yr–1 increase in the lag. This suggests that phenology, one of the most sensitive responses in vegetation, did not keep pace with the recent climate change in human-dominated landscapes. A stable relationship between land surface phenology and climate in human-dominated landscapes is critical to maintaining biodiversity and increasing ecosystem productivity. This study demonstrates a coherent approach to quantify climate-phenology mismatches and to understand their spatial pattern, which can be used to guide sustainable management strategies through selections of species and planting practices in the human-dominated Earth.