Taller trees, which are predominantly canopy species occupying the upper tiers of forests, are outcompeting smaller plants.
As climates around the world continue to change, some species will be winners while others will likely cope much less successfully with changing weather patterns. It has always been like this in the history of life on the planet, but the current pace of change is almost unprecedented.
If we’ve needed any more proof of this, here it comes: numerous plant species in the vast Amazon region have already been losing out to climate change and will continue to do so in coming decades.
So says a team of more than 100 scientists from over 30 institutions worldwide who have set out to evaluate the impact of warming temperatures on thousands of tree species across the Amazon over a three-decade period. They did so by tracking the lifecycles of trees belonging to various species by the help of long-term records. Their findings are disheartening.
Since the 1980’s, global environmental change, including increased temperatures, prolonged droughts and higher levels of atmospheric carbon dioxide, has had measurable impacts on the growth and mortality rates of trees. Moisture-loving tree species have especially been affected, succumbing to environmental changes more regularly than other species.
Nor are these trees being replaced with species more suitable to drier climates at a fast enough space.
“The ecosystem’s response is lagging behind the rate of climate change,” says lead author Dr. Adriane Esquivel Muelbert, from the School of Geography at Leeds University. “The data showed us that the droughts that hit the Amazon basin in the last decades had serious consequences for the make-up of the forest, with higher mortality in tree species most vulnerable to droughts and not enough compensatory growth in species better equipped to survive drier conditions.”
Taller trees, which are predominantly canopy species occupying the upper tiers of forests, are also outcompeting smaller plants, indicating that such canopy-dwelling tree could well become climate change “winners.”
This is because they benefit from increased levels of carbon dioxide in the atmosphere, which allow them to grow more quickly, often at the expense of other species. “This further suggests that higher carbon dioxide concentrations also have a direct impact on rainforest composition and forest dynamics – the way forests grow, die and change,” the researchers explain.
Such findings are invaluable in our quest to understand the impacts of climate change on arboreal ecosystems so we can better protect them from further harm at the hands of loggers and farmers. Called the “lungs of the planet,” the Amazon’s forests boast an estimated 16,000 species of trees with new species being discovered regularly. The health of local forests is key not only to local biodiversity but also to life on the planet in general, seeing as they provide vital carbon capture and storage services whereby they help regulate global temperatures.
Yet a recent study of local trees found, perhaps not surprisingly, that not all species boast the same natural carbon-capture and -storage capacities. An especially carbon-intensive local species is the Brazil nut tree (Bertholletia excelsa), which can reach well over 30m in height and thus dwells in the canopy. These trees alone were found to contain 1.3% of a surveyed forest area’s carbon content. As a result, protecting such towering trees will be all the more important in coming years and decades if we are to keep global temperature rises within manageable limits.
“The impact of climate change on forest communities has important consequences for rain forest biodiversity,” explains Dr. Kyle Dexter, a scientist at the University of Edinburgh, in Scotland. “The species most vulnerable to droughts are doubly at risk, as they are typically the ones restricted to fewer locations in the heart of the Amazon, which make them more likely to be extinct if this process continues,” Dexter adds.
There is a “need for strict measures to protect existing intact rainforests,” he stresses. “Deforestation for agriculture and livestock is known to intensify the droughts in this region, which is exacerbating the effects already being caused by global climate change.”