Permafrost thaw: an important driver of boreal tree cover change

Our recent study on the effects of permafrost thaw and wildfire on boreal tree cover changes in the Taiga Plains has been published in the Geophysical Research Letters. We show that permafrost thaw is equally important as wildfire history to explain recent boreal tree cover dynamics in the Taiga Plains in northwestern Canada by combining 15 years of satellite-derived MODIS tree cover data  with spatial information of wildfire occurrences and permafrost conditions.

Our paper presents, for the first time, a regional-scale analysis of permafrost thaw-induced forest loss in boreal lowlands and confirms that this process, which has been reported in local-scale, site-specific studies, causes widespread alterations to forest structure. Rapid climate change at high latitudes is likely to drastically alter the functioning of northern ecosystems and we show that recent advances in earth observation systems enable us to identify such early signals of climate change impacts on ecosystems. On a regional scale, the identification of direct causes of forest structure changes based on satellite data alone remains challenging. In our study, we present a novel approach to partition the most important drivers of observed forest structure changes across varying scales by combining remote sensing data with information from a wildfire database and a map of permafrost conditions.
Thawing permafrost landscape in the Taiga Plains
Boreal forests cover one quarter of the land surface of Canada, offer important ecosystem services to the society, and are an integral component of the global climate system. The boreal forest provides the essential resource to the timber industry, ensures the livelihood of northern rural and remote communities, and is the habitat for numerous wildlife and waterfowl. It is therefore important to understand how climate change will affect these services to societies and an early detection of forest structure changes represents important information for any risk analysis. Decision-makers need such information to adapt current provincial and federal forest management practices to a rapidly changing northern environment. The Taiga Plains are of particular importance for climate change dynamics since they store a globally significant amount of soil organic carbon. Understanding ecosystem changes, including changes in forest structure and composition, is a precondition to improve our capability to quantify the potential permafrost carbon feedback to global climate.
Helbig, M., Pappas, C., Sonnentag, O. (2016): Permafrost thaw and wildfire: equally important drivers of boreal tree cover changes in the Taiga Plains, Canada. Geophysical Research Letters, 43.