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.