Climate change is advancing spring onset at Acadia and across the National Park System

Monahan, William; Rosemartin, Alyssa; Gerst, Katharine; Fisichelli, Nicholas; Ault, Toby; Schwartz, Mark; Gross, John; Weltzin, Jake

From the abstract: "US national parks – from Alaska to Florida – are already experiencing climate change. Changes in phenology – the timing of seasonal biological events (e.g., leaf-out, migration, and reproduction) – constitute one of the most proximate responses to climate change. Information on phenological changes will support managers in adjusting the timing of activities, such as treating invasive species, operating visitor facilities, and scheduling seasonal events. Here, we evaluate the recent timing of spring onset (past 10-30 years) in Acadia National Park and 275 other parks relative to their historical range of conditions across the past 112 years (1901-2012). Analyses used estimates of spring onset based on predicted dates of first leaf and first bloom derived from indicator plant species and climate data. See Monahan et al. (2016) for complete results and methods. Of the 276 parks examined, spring is advancing in three-quarters, and half are experiencing an “extreme” early spring exceeding 95% of historical conditions, as measured by first leaf index and/ or first bloom index from indicator plant species (Table 1, Figures 3, 4). No parks are experiencing extreme delays in spring onset. Acadia National Park is one of the extreme early spring parks, with both first leaf and first bloom indices earlier than 95% of historical conditions (Figure 1). Managers at Acadia and other “extreme” early parks have already been working under relatively anomalous conditions for the past 10-30 years. Our results demonstrate how changes in climate seasonality are important for understanding ecological responses, and how spatial variability in effects of climate change necessitates localized adaptation approaches."