Trees with faster growth rates die younger across multiple countries and species, which reduces overall carbon storage capacity, a new study claims.
Researchers analysed tree-ring data of more than 200,000 records of 110 species across Europe, Asia and the Americas.
They found tree faster growth, indicated by tree rings, is causing earlier mortality and the release of the carbon back into the atmosphere.
Many scientists believe planting more trees will offset the amount of carbon dioxide (CO2) emissions generated from human activity.
But shorter lifespans of trees will actually make them grow faster and have less time to absorb the CO2 than anticipated, the new study claims.
The new study further calls into question predictions that greater tree growth means greater carbon storage in forests in the long term.
Nothofagus pumilio (southern beeches) forests around Lago Argentino, in the Andes of southern Patagonia, Argentina, showing groups of dead trees. The global analysis reveals that across almost all tree species, fast growing trees have shorter lifespans
An increase in CO2 in the atmosphere – a key ingredient for photosynthesis – can trigger growth spurts for tree species, but too much can have negative consequences
'While it has been known for a long time that fast-growing trees live shorter, so far this was only shown for a few species and at a few sites,' said study author Dr Roel Brienen from the University of Leeds.
'We started a global analysis and were surprised to find that these trade-offs are incredibly common.
'It occurred in almost all species we looked at, including tropical trees.'
Currently, forests absorb large amounts of carbon dioxide (CO2) from the atmosphere, stimulating tree growth.
A relationship between faster tree growth rates and shorter tree lifespan has already been shown in some trees, particularly in cold-adapted conifers.
But whether this applies across species and climates has been disputed.
Tree rings of Hymenaea courbaril (Leguminosae) from the Neotropics. These tree rings formed during the wet season are delimited by visually distinct bands known as marginal parenchyma bands (limits indicated by the white arrows)
Dr Brienen and colleagues analysed a large dataset of tree-ring data representing tree species across all continents except Africa and Antarctica.
Tress can be aged by measuring their girth – specifically the rings that develop over time that increase that girth.
Faster growth, they report, is linked to reduced tree lifespan both across and within tree species.
The trade-off of fast growth rates and slow lifespans has the potential to slow down or even reverse the global forest carbon sink in the future, they say.
Growth-lifespan trade-offs are also near universal, occurring across almost all tree species and climates.
This suggests that increases in forest carbon stocks – carbon sequestered from the atmosphere and stored within the forest ecosystem in living biomass, soil and dead wood – may be short lived.
A reduced future forest carbon sink, which will increase CO2 in the atmosphere in the near future, further increases the urgency to curb greenhouse emissions.
'Our modelling results suggest there is likely to be a time lag before we see the worst of the potential loss of carbon stocks from increases in tree mortality,' said Dr Brienen.
Previous research has shown long-term increases in tree