Trees are among the oldest-living creatures on Earth. But climate change might be making them live fast and die young.
A new international study found that trees are growing faster and dying off earlier, which sets back their capacity to store carbon emissions, according to a new study published last week in Nature Communications.
A team led by Roel Brienen, an ecologist at Leeds University, United Kingdom, looked at tree longevity and growth by measuring more than 210,000 individual tree ring records for a total of 110 trees species across all continents, except Africa and Antarctica.
“By measuring tree rings’ widths one can tell how fast trees grew, while counting rings provides information on tree ages and allows making inferences about trees’ maximum lifespan,” Brienen tells Natalie Parletta of Cosmos.
Earlier research had suggested the same happens in specific tree species, but the new study is the first to suggest this trend is a universal phenomenon, occurring across almost all tree species and climates.
Although it’s unclear why the fast growth is correlated with earlier death, the team offered some potential theories. Trees die when they reach a maximum size and trees that grow faster could be reaching their maximum size sooner.
“This is the most simple explanation, but we can’t conclusively say why,” Brienen tells New Scientist’s Michael Le Page.
The tree’s size could also make them more vulnerable to the environment. “Mortality may increase for big trees as they are more likely to break during storms, be hit by lightning or to die during drought,” Brienen tells Jonathan Chadwick for MailOnline. Diseases and pests could also be the culprit.
Over the past 50 years, land ecosystems have removed about one third of human-made carbon emissions. But in recent decades, carbon dioxide (CO2) emissions — a major factor causing global warming — have increased exponentially. Abundant CO2 and higher temperatures both stimulate rapid tree growth. Rapidly growing trees should mean better CO2 absorption, but the team found that’s not exactly the case in the long-term.
To investigate how fast growth impacts carbon storage, the researchers conducted a computer simulation using data on the black spruce (Picea mariana), reports The Guardian’s Fiona Harvey. They found that if trees live fast and die young, the capacity of global forests to collectively absorb and store CO2 decreases — something already happening in the Amazon.
Increased CO2 compromises forests as a carbon sink, David Lee, an atmospheric scientist at Manchester Metropolitan University who was not involved in the study, tells The Guardian. “The idea that fossil fuel-based emissions can be offset by planting trees or avoiding deforestation really does not stand up to scientific scrutiny,” Lee says.
The researchers say that the tree’s shorter lifespans would give them less time to absorb atmospheric CO2 than anticipated. In other words, MailOnline reports, trees are dying before they're big enough to store significant amounts of carbon from the atmosphere.
The new results could mean that many standard climate change models of how we can use forests as carbon sinks to absorb the CO2 humans produce from fossil fuel burning are likely to overestimate the benefits, The Guardian reports.
“Our society has benefitted in recent decades from the ability of forests to increasingly store carbon and reduce the rate at which CO2 has accumulated in our atmosphere,” says Steve Voelker at SUNY College of Environmental Science and Forestry, according to a press release. “However, 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.”