Plants on the Move: How Climate Change is Impacting Mesoamerican Cloud Forests
The cloud forests of Mesoamerica, known for their misty landscapes, are witnessing a slow yet significant shift. Since 1979, plant species in these regions have gradually migrated uphill at a rate of 1.8 to 2.7 meters per year, seeking refuge from unsuitable climate conditions at their previous altitudes.
“It is an important sign that the ecological impacts of this crisis are more complex than we think,” warns Santiago Ramírez Barahona, the lead author of a pivotal study featured on the March cover of the journal Science. With backing from the Mexican Secretariat of Science and Technology, Ramírez and his colleagues have been probing the susceptibility of these cloud forests to climate change since 2019.
Spanning from Mexico to Panama, cloud forests constitute a mere 1% of the land area, although this percentage is likely smaller today than it was in the 20th century. These forests are home to over 6,000 species of vascular plants, accounting for 18% of the region’s botanical diversity. However, less than 20% of these species are safeguarded. Angela Cuervo from the National Autonomous University of Mexico (UNAM) and co-author of the article highlights, “these forests are one of the most fragile ecosystems.”
The challenge, similar to other parts of Latin America and the Caribbean, lies in the scarcity of data that can track the migration of these trees. Ideally, countries would conduct regular tree censuses to monitor species movements every few years. Due to the absence of such data in Mesoamerica, researchers had to devise alternative methods.
The research team initially focused on identifying the necessary data. After evaluating various sources, they opted for the Global Biodiversity Information Facility, which compiles global scientific data on species, including their locations and the years they were recorded. They downloaded data from the past 30 years and combined it with elevation and relief data from satellite imagery to map the migration of 1,021 plant species in Mesoamerica’s cloud forests.
The study revealed that approximately 380 species, or 36%, have ascended to higher altitudes to evade the conditions induced by climate change and deforestation. The shifting climate conditions are trapping the most vulnerable plants, unable to move downward due to increased temperatures and struggling to adapt to cooler altitudes. Deforestation poses an additional threat.
Not all species are responding uniformly. “What has made me think the most is that only a third, and not all, plants are moving,” says Ramírez. He likens the situation to cockroaches scattering in different directions when a light is turned on, each plant species reacting individually. The intricate relationships among plant species, developed over millennia, are now being disrupted by climate change.
“It could be understood as a disintegration of the forest, which, even in human terms, would cease to function, because many of these ecosystems provide us with water,” explains the biologist. The cloud forests’ humidity is so intense that, even on dry days, stepping inside the forest canopy feels like walking in a drizzle.
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