Trees that grow quickly have a shorter lifespan, which is terrible news for fighting the climate crisis because they stop storing carbon. In a recent tree study, researchers found that certain tree species grow faster than others, and the faster trees grow, the quicker they die.
Researchers already knew that fast-growing trees, such as the conifer species in cold areas, are likely to have shorter lifespans. What they didn’t realize was as global warming accelerates, the impact of warmer climates can boost tree growth.
The study, published in the journal Nature Communications, describes how the association between faster growth and shorter lifespan appears across a wide range of tree species and latitudes. “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,” said assoc. Prof. Roel Brienen, the study’s lead author.
Trees reach their maximum size sooner in warmer climates, and that appears to raise their chances of dying. Fast-growing trees may be more vulnerable to factors like drought, disease, and pests. As trees die, they gradually release their stored carbon in the form of greenhouse gases.
These findings suggest that ‘standard climate change models’ of how forests can be used as carbon sinks to absorb the CO2 we produce from burning fossil fuel are likely overestimating the benefits. The study indicates that while forests of the future might grow faster as temperatures rise, they could also store less carbon as trees die sooner.
Steve Voelker, a co-author of the study, explained:
Our findings 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. The 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.
For the analysis, the team examined data from over 200,000 tree ring samples on behalf of 110 tree species across all continents except Antarctica and Africa. They found that quicker growth was accompanied by shorter lifespans in trees across different species, and of the same species; while showing no sign of dependency on the soil or climate.
To see what effect faster growth would have on carbon storage, the researchers conducted a computer simulation, collected data on the black spruce (Picea mariana). The results showed that as temperatures rise, the greater propensity for the trees to perish after growing faster could diminish the capacity of global forests to absorb and store CO2.
Preserving existing forests and growing millions of trees are efficient ways of lessening the impacts of global warming. However, as the climate isn’t getting any cooler, several studies have cast doubt on the efficiency and capacity of global forests acting as carbon sinks. In March 2020, a study found that the world’s tropical forests were losing their ability to store carbon, primarily due to CO2 overload. The scientists found that when levels of CO2 rise, most plants thicken their leaves; but, plants with thicker leaves might intensify the effects of climate change as they would be less efficient in absorbing atmospheric carbon.
