Global change is predicted to increase temperature substantially in the North as well as altering run-off regimes with less synchronicity as the importance of snow melt declines. River biota and ecosystem processes will be influenced across all levels of organization, both in concert and individually. It is of vital importance that the impacts, and their likely magnitude, can be identified in order to deploy suitable adaptation strategies at the catchment scale. In this paper, we re-analyse four data sets from studies conducted in Greenland (66–69oN), Iceland (64oN), Sweden (60oN) and Denmark (55–57oN) to try and tease out the likely impacts of water temperature and hydrology in shaping the stream communities and ecosystem processes in high-latitude catchments. Water temperature was the environmental variable that best explained macroinvertebrate community composition across latitudes. In contrast, no significant relationship between macroinvertebrate community composition and measures of hydraulic stability (or nutrients) was found. We found a strong linear relationship between decay rate of leaf litter and water temperature (r2 = 0.68; p < 0.0001) independent of latitudes. Our study suggests that temperature could be the primary driver of ecosystem change in future with northern catchments likely to be especially vulnerable. Copyright © 2012 John Wiley & Sons, Ltd.