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Abstract:
The Paris Agreement promotes forest management as a pathway towards
halting climate warming through the reduction of carbon dioxide (CO2)
emissions(1). However, the climate benefits from carbon sequestration
through forest management may be reinforced, counteracted or even offset
by concurrent management-induced changes in surface albedo, land-surface
roughness, emissions of biogenic volatile organic compounds,
transpiration and sensible heat flux(2-4). Consequently, forest
management could offset CO2 emissions without halting global temperature
rise. It therefore remains to be confirmed whether commonly proposed
sustainable European forest-management portfolios would comply with the
Paris Agreement-that is, whether they can reduce the growth rate of
atmospheric CO2, reduce the radiative imbalance at the top of the
atmosphere, and neither increase the near-surface air temperature nor
decrease precipitation by the end of the twenty-first century. Here we
show that the portfolio made up of management systems that locally
maximize the carbon sink through carbon sequestration, wood use and
product and energy substitution reduces the growth rate of atmospheric
CO2, but does not meet any of the other criteria. The portfolios that
maximize the carbon sink or forest albedo pass only one-different in
each case-criterion. Managing the European forests with the objective of
reducing near-surface air temperature, on the other hand, will also
reduce the atmospheric CO2 growth rate, thus meeting two of the four
criteria. Trade-off are thus unavoidable when using European forests to
meet climate objectives. Furthermore, our results demonstrate that if
present-day forest cover is sustained, the additional climate benefits
achieved through forest management would be modest and local, rather
than global. On the basis of these findings, we argue that Europe should
not rely on forest management to mitigate climate change. The modest
climate effects from changes in forest management imply, however, that
if adaptation to future climate were to require large-scale changes in
species composition and silvicultural systems over Europe(5,6), the
forests could be adapted to climate change with neither positive nor
negative climate effects.
