While water challenges are global, the water cycle in boreal regions is perhaps uniquely vulnerable due to cumulative effects of land use and climate warming, with the latter proceeding at faster rates at high latitudes (Buntgen et al. 2021). Climate change in the north is predicted to give rise to increasingly snow-free winters and warmer summers in boreal landscapes, which collectively will reduce water storage. Superimposed on these changes are barriers or inertia due to past land-use decisions, that may exacerbate pressures on ground- and surface waters. The most widespread management activity in many boreal countries is the historical ditching of wet soils. Forest ditches are constructed waterways that were dug, often by hand, to remove excess water affecting several million hectares of land, especially in Finland and Sweden, but also in many other northern countries (Strack, 2008; Fig 1). This resulted in improved forest growth and transformed wet soils and peatlands to productive forests, but also came with unwanted environmental consequences.
Drainage ditches are sources of enhanced methane emissions (Peacock et al. 2021) and elevated dissolved organic carbon concentrations (Nieminen et al. 2021). Low water tables also lead to enhanced soil carbon mineralization and increased terrestrial greenhouse gas (GHG) emissions (Evans et al. 2021). The biogeochemical properties of these extensions to the drainage network dramatically alter our understanding of running waters as sources of GHGs to the atmosphere and the overall provisions of ecosystem services. Most importantly, in an era increasingly affected by climate change, we now face conditions that create the opposite obstacle that the ditches aimed to solve – insufficient amounts of water – due to the expected increase in frequency, duration and severity of drought (Spinoni et al. 2021). Historical ditching may thus create enhanced vulnerability to drought in the future, which would require massive efforts to reverse.