Trees in Brazil’s Atlantic Forest are undergoing a complex migration as the planet continues to face the consequences of rising temperatures in response to climate change.
A new study published today in the Journal of Vegetation Science shows that trees in the Brazilian Atlantic Forest are migrating in response to the changing climate. Stretching over 3,000 kilometers along Brazil’s coast and inland to Argentina and Paraguay, the forest is home to a vast array of plant and animal species.
However, centuries of deforestation and habitat destruction have reduced the forest by around 85%. Now, tree species within these mountain forests are moving. Some have slowly migrated uphill to escape the heat, while some trees in the lowland forests are migrating downhill. While the movement of trees to more suitable climates is a long-recognized phenomenon, the speed at which these well-rooted plants move remains somewhat mysterious.
The current migration is not straightforward, as various factors, such as competition between species and the availability of suitable habitats, influence it. The younger trees in high-altitude forests are more adaptable and move uphill, indicating that they are better equipped to handle the changing temperatures.
“We found that different species are moving in different directions – in lower forests, trees are moving downhill more often than uphill, probably due to factors besides temperature, like competition between species,” explained lead author Dr. Rodrigo Bergamin in a press release. “However, in the forest higher up in the mountains, most species are moving uphill as temperatures rise and the undergrowth becomes more suited to those trees favouring warm temperatures. This could mean that species needing colder temperatures are at risk of dying out as the world continues to warm.”
The consequences of this migration are far-reaching. As trees move to new areas, they are leaving behind the delicate ecosystems they once supported. This can lead to the extinction of species that are unable to adapt to the changing conditions.
According to the study, the researchers calculated “community temperature scores” across 627 tree species living in 96 different locations in the Brazilian Atlantic Forest. This allowed them to develop a thorough understanding of the climactic pattern of the forest.
“Species from higher altitudes are generally more sensitive to temperature, and those that need cold are more likely to lose out in competition under warmer temperatures to species that prefer hotter temperatures,” explained Dr. Sandra Müller from the Federal University of Rio Grande do Sul, and one of the study’s authors.
While the planet’s current heating is unprecedented and a serious threat, trees have been moving around for millions of years. For example, roughly 14,000 years ago, areas around New York and New England were home to vast forests of spruce trees, and during a brief 2,000-year cold snap, those spruce trees moved on and were replaced by pine trees. Then, the planet warmed, and those pines were pushed out by deciduous trees such as birch, maple, and oak trees.
Ancient forests moved around constantly due to temperature and rainfall patterns, infections and diseases caused by pathogens and pests, and even massive forest fires that would alter the landscape. Moreover, the situation is further complicated by the phenomenon known as Reid’s Paradox.
First noted by Clement Reid, a paleobotanist, in 1899, there is an apparent contradiction between the observed rapid migration of plants and the expected slow migration based on genetic adaptation. Basically, trees migrate far too fast simply by growing up, dropping seeds, and then growing again. Their genetic need to keep their species alive by making copies of themselves via seeds in a specific and more climate-friendly direction does not account for how fast they actually do it. Something else is moving those seeds around and at greater distances. Scientists note that other species, such as birds or small mammals, help trees migrate along, but this would only account for a small portion of tree migrations.
Scientists are still stumped by Reid’s Paradox, but it’s clear that as trees migrate, they respond to changing temperatures, interact with other species, and adapt to new environments. This complex interplay makes it challenging to predict the exact consequences of climate change on ecosystems.
In this latest study, the researchers are concerned that the warming planet will make tree migration more competitive and, in turn, destroy entire ecosystems. Although such factors make predictions difficult, there is still hope. Studies have shown that forest transition, or the recovery of forests after disturbance, is possible if environmental and land regulations are implemented effectively. By understanding the conditions under which forests can recover, policymakers can develop strategies to protect and restore these vital ecosystems.
The authors note that the Brazilian Atlantic Forest tree migration is not just a local issue, but a global concern. As one of the most biodiverse regions on Earth, its preservation is crucial for maintaining the health of the planet. The loss of this forest would have far-reaching consequences, including the loss of carbon sequestration, soil erosion, and the displacement of indigenous communities.
“This study showed what is happening in the South of the Atlantic Forest, but different regions might show other trends,” explained study co-author Dr Adriane Esquivel Muelbert. “We are now bringing together researchers from across the whole biome to create a big picture of how these forests are responding to global change.”
MJ Banias covers space, security, and technology with The Debrief. You can email him at mj@thedebrief.org or follow him on Twitter @mjbanias.