Maybe there should be a companion to Aesop’s fable about the tortoise and the hare. This one could be about the spruce and the poplar.
Fast-growing trees like poplars might seem likely to win the race to soak up carbon the fastest, making them ideal candidates for tree-planting campaigns aimed at helping to address climate change. But it turns out that slower sprouting trees, like the spruce, are frequently the growth champions.
Outside of tropical rainforests or cozy, moist greenhouses favored by labs studying plants, trees that have long been considered “fast” aren’t so speedy after all, according to research published last week in Nature.
The findings suggest that tree planters shouldn’t be seduced by the promises of certain trees that might not be best suited for harsh conditions. And it sheds light on a disconnect that has puzzled scientists.
For years, lab experiments have shown that trees with certain characteristics grow more quickly – ones that have large leaves to capture more sunlight and store more nitrogen or roots able to suck up more water. But out in the woods, results were less emphatic. While some field research found a connection between these traits and tree growth, others found only a weak or inconsistent link.
What was going on?
To make sense of this, a team of scientists, led by researchers from two French institutions – Bordeaux Sciences Agro and the French National Research Institute for Agriculture, Food, and Environment (INRAE) – went big. The gathered data from research tracking 223 different tree species in 160 experimental research forests around the world. Then they looked for patterns revealing how tree growth correlated with different plant traits.
Some trees had the characteristics of classic fast growers, built to prioritize sucking up water, nutrients and sunlight. Others fit the bill for slow growers more focused on conserving resources than bingeing on them.
The data revealed that in most parts of the world it was the conservative trees – the tortoises of the arboreal world – that grew faster. The only place where growth rates were a tiny bit higher for supposed fast-growers was in places such as a rainforest that were warm, wet and rich with nutrients. While such conditions might be heaven for plants, they’re also not found in most of the world.
The trees that grew faster in ideal conditions typically “are more sensitive to environmental harshness, whereas conservative, stress-tolerant tree species perform better in most environments,” the scientists concluded.
The chief lesson, according to the scientists, is something that many a wise forester would probably tell you: Plant trees that are adapted to the environment where you are putting them. And don’t underestimate the strength of the tortoise.
Augusto, et. al. “Widespread slow growth of acquisitive tree species.” Nature. March 19, 2025.
Photo: The common alder (Alnus glutinosa) is an example of tree species that are more efficient at conserving their resources rather than extracting external resources, so-called conservative species. ©The German Centre for Integrative Biodiversity Research (iDiv)
