Abstract
AbstractIn Nordic and Arctic regions, the rapidly warming climate sustains hydroclimatic and vegetation changes in the landscape. There is evidence for an increase in vegetation density in some regions, a trend that is expected as a response to increasing temperature and precipitation. If the hydroclimatic changes are linked to vegetation response, it could be viewed as a landscape‐scale nature‐based solution (NBS) that could moderate the runoff response, as denser vegetation should lead to increased evapotranspiration and lower runoff. In this paper, we investigate and compare hydroclimatic changes over a set of basins in the Nordic region and northwest America and compare with changes in vegetation density, analyzed using the normalized difference vegetation index (NDVI) for three time periods: 1973–1978, 1993–1998, and 2013–2016.Over the period of the 1970s to 1990s, the hydroclimate became warmer and wetter and vegetation density increased, but over a later period from the 1990s to 2010s, vegetation density decreased, despite a continuing warming and wetting of the climate. Although there was a tendency for runoff to decrease in basins where vegetation density increased, the relation between precipitation and runoff was much stronger. Overall, we found weak evidence for vegetation density changes, driven by hydroclimate, to act as NBS on the landscape scale over the studied regions. However, as hydroclimatic changes interact with vegetation changes and their ensuing hydrological responses in complex ways, more detailed investigations are needed to determine the potential NBS effect on the landscape scale across Nordic and Arctic regions.
Highlights
Hydroclimatic change in the Nordic and Arctic regions has hitherto been much more intense than the global average, and substantial changes have been documented (Gisladottir, Arnalds, & Gisladottir, 2005; Karlsson, Bring, Peterson, Gordon, & Destouni, 2011; Prowse, Bring, Mård, & Carmack, 2015; Prowse, Bring, Mård, Carmack, Holland, et al, 2015; Rennermalm, Bring, & Mote, 2012; Land Degrad Dev. 2018;29:3663–3673.wileyonlinelibrary.com/journal/ldr 3663 GROß ET AL.Sjöberg, Frampton, & Lyon, 2013)
We investigated whether vegetation density has increased in six different study areas in the Nordic region and northwest America and whether hydroclimate changes support the notion of climate‐driven vegetation change as a landscape‐scale nature‐based solution (NBS) for these regions
From the 1990s to the 2010s, changes in precipitation were smaller and more variable, and patterns of vegetation change generally shifted direction, giving an overall vegetation density decrease. Considering these results and the general pattern of runoff response to vegetation density in the study areas, there was some evidence of a runoff moderating effect of vegetation density, but this effect was relatively weak and not consistent across all study areas and periods
Summary
Both temperature and precipitation are increasing, because the capacity to hold water vapor increases with higher temperatures (Francis et al, 2009). Subarctic, and Arctic climates, higher temperature and precipitation typically enhance vegetation productivity and diversity (Francis et al, 2009). General greening, or increased vegetation density, can be expected in northern and Arctic landscapes, when not considering other drivers that modify vegetation, such as anthropogenic land management. These changes have been investigated throughout the Arctic (e.g., Myers‐ Smith et al, 2015; Naito & Cairns, 2011). The term ‘shrubification’ is used to describe the increasing propensity for shrub vegetation growth in landscapes that were previously dominated by open tundra (Pearson et al, 2013; Tape, Sturm, & Racine, 2006)
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