Revaluing unmanaged forests for climate change mitigation

Abstract

BackgroundUnmanaged or old-growth forests are of paramount importance for carbon sequestration and thus for the mitigation of climate change among further implications, e.g. biodiversity aspects. Still, the importance of those forests for climate change mitigation compared to managed forests is under controversial debate. We evaluate the adequacy of referring to CO2 flux measurements alone and include external impacts on growth (nitrogen immissions, increasing temperatures, CO2 enrichment, changed precipitation patterns) for an evaluation of central European forests in this context.ResultsWe deduce that the use of CO2 flux measurements alone does not allow conclusions on a superiority of unmanaged to managed forests for mitigation goals. This is based on the critical consideration of uncertainties and the application of system boundaries. Furthermore, the consideration of wood products for material and energetic substitution obviously overrules the mitigation potential of unmanaged forests. Moreover, impacts of nitrogen immissions, CO2 enrichment of the atmosphere, increasing temperatures and changed precipitation patterns obviously lead to a meaningful increase in growth, even in forests of higher age.ConclusionsAn impact of unmanaged forests on climate change mitigation cannot be valued by CO2 flux measurements alone. Further research is needed on cause and effect relationships between management practices and carbon stocks in different compartments of forest ecosystems in order to account for human-induced changes. Unexpected growth rates in old-growth forests – managed or not – can obviously be related to external impacts and additionally to management impacts. This should lead to the reconsideration of forest management strategies.

Estimating net climate impacts of timber production and utilization in fossil fuel intensive material and energy substitution

“…According to the results the unmanaged forests provided only limited possibilities for climate change mitigation compared to the possibilities to store carbon in wood based materials and to substitute materials and fuels in energy production. Our results support earlier studies (Klein et al 2013, Krug et al 2012 and indicated that drawing a system boundary excluding carbon storage and substitution effects of harvested biomass may produce variable results as seen, for example in Naudts et al (2016).…”

How can forest management increase biomass accumulation and CO2 sequestration? A case study on beech forests in Hesse, Germany

“…This is especially difficult in uneven-aged forest stands. On top of this, common yield tables tend to be outdated since additional impacts, like an enhanced CO 2 concentration, nitrogen (N) depositions, and changed precipitation and temperature patterns, have initiated increased growth rates [5][6][7].…”

“…Further, most discussions do not differentiate between direct human-induced and other human-induced impacts, like increased concentrations of CO 2 or increased N deposition, a prolonged vegetation period, or changed precipitation rates. Those indirect human-induced impacts also lead to increased forest growth but cannot be attributed to forest management practices, as the impacts affect managed as well as unmanaged forest [6]. Since it is quite difficult, if possible at all, to determine the effect of such "other" human-induced impacts than management, only a direct comparison of managed and unmanaged forests can allow a conclusion on the impact of management on superior biomass development and, from this, the impact on carbon sequestration.…”

Distribution and Factors Influencing Organic Carbon Stock in Mountain Soils in Babia Góra National Park, Poland

“…In the study in [17], the land-use system and altitude were shown to be important factors in the regulation of SOM decomposition by altering the natural soil characteristics. Unmanaged or old-growth forests are important for carbon sequestration [18].…”