We synthesized an expert review of climate change implications for hydroecological
and terrestrial ecological systems in the northern coastal temperate rainforest of North America.
Our synthesis is based on an analysis of projected temperature, precipitation, and snowfall
stratified by eight biogeoclimatic provinces and three vegetation zones. Five IPCC CMIP5
global climate models (GCMs) and two representative concentration pathways (RCPs) are the
basis for projections of mean annual temperature increasing from a current average (1961–1990) of 3.2 °C to 4.9–6.9 °C (5 GCM range; RCP4.5 scenario) or 6.4–8.7 °C (RCP8.5), mean
annual precipitation increasing from 3130 mm to 3210–3400 mm (3–9 % increase) or 3320–
3690 mm (6–18 % increase), and total precipitation as snow decreasing from 1200 mm to
940–720 mm (22–40 % decrease) or 720–500 mm (40–58 % decrease) by the 2080s (2071–
2100; 30-year normal period). These projected changes are anticipated to result in a cascade of
ecosystem-level effects including: increased frequency of flooding and rain-on-snow events;
an elevated snowline and reduced snowpack; changes in the timing and magnitude of stream
flow, freshwater thermal regimes, and riverine nutrient exports; shrinking alpine habitats;
altitudinal and latitudinal expansion of lowland and subalpine forest types; shifts in suitable
habitat boundaries for vegetation and wildlife communities; adverse effects on species with
rare ecological niches or limited dispersibility; and shifts in anadromous salmon distribution
and productivity. Our collaborative synthesis of potential impacts highlights the coupling of
social and ecological systems that characterize the region as well as a number of major
information gaps to help guide assessments of future conditions and adaptive capacity.
