Forest carbon sink neutralized by pervasive growth-lifespan trade-offs

Abstract

Land vegetation is currently taking up large amounts of atmospheric CO2, possibly due to tree growth stimulation. Extant models predict that this growth stimulation will continue to cause a net carbon uptake this century. However, there are indications that increased growth rates may shorten trees′ lifespan and thus recent increases in forest carbon stocks may be transient due to lagged increases in mortality. Here we show that growth-lifespan trade-offs are indeed near universal, occurring across almost all species and climates. This trade-off is directly linked to faster growth reducing tree lifespan, and not due to covariance with climate or environment. Thus, current tree growth stimulation will, inevitably, result in a lagged increase in canopy tree mortality, as is indeed widely observed, and eventually neutralise carbon gains due to growth stimulation. Results from a strongly data-based forest simulator confirm these expectations. Extant Earth system model projections of global forest carbon sink persistence are likely too optimistic, increasing the need to curb greenhouse gas emissions.

Variations of carbon allocation and turnover time across tropical forests

“…In agreement with the “grow fast, die fast” hypothesis of an inverse relationship between growth (defined as woody/leaf productivity) and turnover time, we find such an inverse spatial relationship between growth and turnover time for leaves and wood across all tropical forests (Figure 6a,b). Previous studies using tree‐ring data or ground measurements suggested a similar spatial trade‐off between growth and tree life span (Brienen et al, 2020; Büntgen et al., 2019; Wright et al, 2010). However, our analysis suggests that this trade‐off exists not only at the ecosystem level but also at the organ level.…”

“…At the plot level, carbon allocation and turnover time within the major carbon pools have been measured (Chen et al., 2013; Keeling & Phillips, 2007; Xue et al., 2017), but information on large‐scale patterns of carbon allocation and turnover is still lacking. Moreover, using tree‐ring data or ground measurements, previous studies found a trade‐off between the growth and the life span of trees (Brienen et al, 2020; Stephenson & van Mantgem, 2005), but it still remains unknown whether the hypothesis of “grow fast, die fast” holds good at the ecosystem scale.…”

Saving the Planet with Appropriate Biotechnology: 5. An Action Plan

“…"… Faster growth has a direct and negative effect on tree lifespan, independent of the environmental mechanisms driving growth rate variation. Growth increases, as recently documented across high latitude and tropical forests, are thus expected to reduce tree lifespans…" and that "… recent increases in forest carbon stocks may be transient due to lagged increases in mortality …" (quoted from Brienen et al, 2020).…”

“…Brandão et al (2013) indicate that even if the carbon storage is temporary, any carbon removal and storage from the atmosphere has the potential to mitigate climate change. However, there is firm evidence that current projections of global forest carbon sink persistence are too optimistic because the increased growth rates of trees caused by increased levels of CO2 in the atmosphere may shorten the lifespan of forest trees (Brienen et al, 2020):…”

Artenschutz und Europarecht im Kontext der Windenergie – Der Klimaschutz und die Auslegung der Ausnahmeregelungen der Vogelschutzrichtlinie

“…Bezogen auf die artenschutzrechtliche Rechtfertigung des Baus und Betriebs von Windenergieanlagen bedeutet dies, dass auf die Schäden zu blicken ist, die an den genannten Schutzgütern eintreten würden, bliebe man untätig. Da der Klimawandel absehbar mit einer erhöhten CO 2 -Konzentration der Luft verbunden ist und dies Auswirkungen auf das Pflanzenwachstum hat, 71 sind die erforderlichen ursächlichen Zusammenhänge und Risiken dem Grunde nach bekannt. Daher kann es nicht erstaunen, wenn schon seit einiger Zeit landwirtschaftliche Anpassungsstrategien entwickelt werden, um die Schäden möglichst klein zu halten.…”