Tropical trees are moving up the mountain to avoid climate change
Tree populations “migrate” upwards – but perhaps not fast enough to ensure their survival
An international team of scientists, including researchers from the University of Göttingen, has discovered that tropical and subtropical forests in the South American Andes are reacting to global warming. They "migrate" to higher, cooler altitudes to avoid the rise in temperature. However, they are probably not fast enough to avoid biodiversity loss. The results were published in the journal Nature.
"This study confirms for the first time that trees from the Andes and Amazon forests of Colombia, Ecuador, Peru and northern Argentina, like many other plant and animal species around the world, are migrating upwards," says first author Belén Fadrique of the University of Miami, USA. The problem, however, is that these tropical trees then encounter other environmental difficulties at higher, cooler altitudes that then threaten their survival.
In the Andes, the ecosystems can change very fast and very dramatically between different altitudes - from sunny and sometimes dry forests at the transition to the Amazon lowlands, to sopping-wet cloud forests. These thresholds, also known as ecotones, seem to block the migration of species. Some tree species, for example, which are trying to climb to higher altitudes due to changes in conditions, may not find a suitable habitat there because the rainfall or light conditions don’t suit them.
The scientists investigated the conditions of thousands of mountain trees on 186 study sites. Most of these forest plots are at altitudes of 300 to 3000 metres above sea level and are about the size of a football field. Their conclusion: the number of warmth-loving species is increasing, while the number of cold-loving species is decreasing. According to the authors, so-called "thermophilization" means that those species that prefer the cold are displaced or even made extinct, while the more heat-tolerant species take over their space.
"This negative climate change effect is further exacerbated by other direct and indirect human influences such as high deforestation rates and increasing nutrient deposition," stresses Dr Jürgen Homeier of the Department of Plant Ecology and Ecosystems Research at the University of Göttingen, co-author of the study. Andean forests must therefore be included in the growing list of ecosystems that are unable to react quickly and coherently to climate change and are thus exposed to a high risk of loss of their biological diversity and functionality. Long-term studies are needed to better understand the underlying mechanisms.
Widespread but heterogeneous responses of Andean forests to climate change. Belén Fadrique et al. Nature (2018). Doi: https://doi.org/10.1038/s41586-018-0715-9
Dr Jürgen Homeier
University of Göttingen
Department of Plant Ecology and Ecosystems Research
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