The European forest carbon budget under future climate conditions and current management practices

[摘要] To become carbon neutral by 2050, the European Union (EU27) netcarbon sink from forests should increase from the current level of about −360 to −450  Mt CO 2eq  yr −1 by 2050. Reachingthis target requires additional efforts, which should be informed by theexpected interactions between current age-class distributions, the effect offorest management practices and the expected impacts of future climatechange. However, modelling the combined effect of these drivers ischallenging, since it requires a mechanistic assessment of climate impacts onprimary productivity and heterotrophic respiration and a detailedrepresentation of the forest age structure and of the management practicesacross the entire EU. To achieve this goal, we combined the output providedby four land–climate models – run under two different RepresentativeConcentration Pathway scenarios (RCP2.6 and RCP6.0) – to parameterize theinput data used in an empirical forest growth model. This hybrid modellingapproach aims to quantify the impact of climate change and forest managementon the long-term (i.e. to 2100) evolution of the EU27  +  UK forest carbonbudget. This approach was tested using a business-as-usual (BAU) scenario,based on the continuation of the management practices applied by EU memberstates within the historical period 2000–2015. We emphasize that our studydoes not explore a specific policy scenario but describes a methodologicalframework. Our results highlight that, under our BAU case, the EU27  +  UK forest C sinkwould decrease to about −250  Mt CO 2eq  yr −1 in 2050 and −80  Mt CO 2eq  yr −1 by 2100. The main driver of the long-term evolution ofthe forest C sink is the ongoing ageing process of the European forests,mostly determined by past and ongoing management. In addition, climatechange may further amplify or mitigate this trend. Due to the largeuncertainty in climate projections, in 2050 the net C sink may range from −100 to −400  Mt CO 2eq  yr −1 under RCP2.6 andfrom −100 to −300  Mt CO 2eq  yr −1 under RCP6.0. These resultssuggest that while a change in management practices would be needed toreverse an otherwise declining trend in the sink, climate change adds aconsiderable uncertainty, potentially nearly doubling or halving the sinkassociated with management.

[学科分类] 大气科学