There’s a universal trade-off between early growth and lifespan in trees, according to a new study, which showed faster growth has a direct and negative effect on the lifespan of trees. This could mean bad news for the climate crisis, challenging the idea that greater growth would mean greater carbon storage.
Trees grow faster in warmer areas of the planet and this should help stop global warming, as they can absorb more carbon dioxide from the air as they grow. But this apparently beneficial cycle was questioned by a new study, which showed the faster trees grow, the sooner they die — no extra carbon included.
“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,” Roel Brienen, lead author, said in a statement. “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.”
For decades forests have provided an important carbon sink, especially as global warming started to kick in. However, Brienen and his team recently found that carbon accrual in the Amazon had declined by a third since the 1990s. This led them to explore the link between tree growth and longevity in as many species as possible.
Their new study is the largest one so far to look at the link between the growth and lifespan of trees. The researchers looked at more than 200,000 tree-ring records from 82 tree species from sites around the globe. They confirmed that the accelerated growth led to a shorter lifespan and that this happened in all species and climates.
The researchers suggested that the growth-lifespan trade-off is due to a higher risk of dying, as trees reach their maximum potential tree size sooner. But other factors also play a role. For example, trees that grow faster invest less in defenses against diseases or insect attacks.
“Our findings, very much like the story of the tortoise and the hare, indicate that there are traits within the fastest growing trees that make them vulnerable, whereas slower growing trees have traits that allow them to persist,” said co-author Steve Voelker. “Carbon uptake rates of forests are likely to be on the wane as slow-growing and persistent trees are supplanted by fast-growing but vulnerable trees.”
This would eventually reverse any carbon storage gains and diminish hopes for the future capacity of the terrestrial carbon sink, requiring the world to reduce its emissions much faster.
However, this doesn’t mean trees aren’t relevant in mitigating the climate crisis. Keith Kirby, woodland ecologist at the University of Oxford, not involved in the study, told The Guardian that despite the world can’t rely as much on the growth of trees to enhance forest carbon sink potential, this could be offset by slowing deforestation and expanding forests.