Report on the observed climate, projected climate, and projected biodiversity changes for Acadia National Park under differing levels of warming

Acadia National Park is among the top 29% of all non-marine protected areas, globally. Much of the park is moderately resilient to climate change, even with higher levels of warming. The highest areas (e.g., Cadillac Mountain) are more resilient than areas at sea level. Averaged over the entire area, with 4°C warming (global, above pre-industrial), the area is projected to remain climatically suitable for 62.6% of its terrestrial biodiversity (fungi, plants, invertebrates, and vertebrates), with 2.4% of its area remaining an overall refugia (remaining climatically suitable for >75% of the species) for biodiversity. However, if warming levels were held to 2°C, 95.5% of the area would remain a climatic refugia and the area would remain climatically suitable for 84.6% of its terrestrial biodiversity. Thus, holding warming to 2°C or below would make a large difference in the resilience of the park.
Between 1961-1990 and 1991-2020 the average monthly temperature has increased by 0.2° - 1.8°C (December). With warming levels of 2.0°C the new average monthly temperature is equivalent to that only seen 1 in 20 years in 1961-1990 for June – October. All but three months have seen increases in precipitation, but May, August, and November have been drier. Models project that most months will become wetter except for September. The number of months with severe drought has declined slightly between 1961-1990 and 1986-2015, while those being waterlogged have increased.
Biodiversity adaptation options generally allow for business-as-usual conservation, especially at higher elevations, taking into account changes in extreme events (especially heat). However, lower elevation areas would need some additional adaptation effort, especially with warming levels of 3°C and above.