The ecology of these lakes has reached a point of no return as a result of climate change. In the past there will be decreases in diatome biodiversity, but it is produced in specific cases that are quickly recovered. Now the loss of species is caused by the entire island: biodiversity decreases and ecosystems become simpler.This is what it reveals a study in which the CEAB-CSIC researcher Teresa Buchaca has participated.
The increase in temperature caused by climate change is endangering the lake ecosystems of the Azores archipelago. These lakes, which are important to the population as water reserves, contribute to water regulation, tourism, and recreational activities, and are essential for preserving the islands’ biodiversity, are losing part of their biodiversity and their ability to provide these ecosystem services. This is confirmed by the study conducted on the island of São Miguel, where they have observed how the number of diatom species, unicellular algae that form the base of the food chain, decreased by 27% in all the lakes on the island since 1982, when the temperature in the Northern Hemisphere increased by 0.35ºC compared to the 20th-century average. It is likely that the changes detected in the lakes of the archipelago are also occurring in other lake ecosystems around the world.
“What is most alarming about this data is not the nearly 30% reduction in diatom species in a lake, but the fact that it is a decrease that we have seen happening on a regional scale across the entire island, which indicates that homogenization is occurring,” warns Miguel Matías, a researcher at the National Museum of Natural Sciences. “Thanks to the sedimentary records we have, which in some lakes date back four to five thousand years, we know that these declines in diatom diversity have occurred in specific lakes due to environmental disturbances, but not across an entire island as is happening now. Moreover, these were isolated declines from which the ecosystem easily recovered,” he continues.
There are around 20,000 different species of diatoms, and this group is used as a reference to understand the environmental conditions of an ecosystem, as well as to study climate changes that have occurred throughout Earth’s history. “In the Azores, changes in these algae communities have been observed since humans began expanding across the archipelago. With this study, we have confirmed that in 1982, a threshold was crossed, a point of no return, that has homogenized the lakes at a regional level, leading to a reduction in their ecosystem services,” explains Sergi Pla-Rabés, a researcher at the Autonomous University of Barcelona and CREAF.
According to research published in the journal Nature Communications Earth & Environment, the combination of anthropogenic disturbances in the ecosystem has led to the development of phytoplankton composed of smaller algae and cyanobacteria, often accumulating on the surface, which prevents sunlight from reaching deeper areas of the water body. As the availability of light decreases, the habitat available for benthic diatoms and the number of species are reduced, deeply simplifying the ecosystem,” comments Vítor Gonçalves from the University of the Azores. “Our hypothesis is that this homogenization that we have documented on the island of São Miguel is occurring in lake ecosystems of insular areas and possibly in isolated lake regions in the Northern Hemisphere and around the world,” adds Sergi Pla-Rabés.
Next objective: restoring the ecosystems
With this data in hand, it is essential to increase ecological restoration processes to enhance environmental diversity across the island. “The degradation of ecosystems is not something that can be completely reversed; we cannot aim to return to the environmental situation that existed in the past, as if there were no human populations on the islands,” warns Pedro Raposeiro, also from the University of the Azores.
The team’s proposal to increase ecosystem complexity, ensuring that the necessary ecosystem services for the island’s population are maintained, is to reduce local pressures that we can control. “We believe it is necessary to focus efforts on specific areas of the island, ensuring that livestock farming and infrastructure are kept outside the lake basins. Ultimately, it’s about practicing ecological restoration that takes into account the economic and social situation of those living on the island,” concludes Vítor Gonçalves, a researcher at the University of the Azores.
Researchers from the Autonomous University of Barcelona (UAB), CREAF, the National Museum of Natural Sciences (MNCN-CSIC), Geosciences Barcelona (GEO3BCN-CSIC), the Centre for Advanced Studies (CEAB-CSIC), and the Universities of the Azores, Évora, Coruña, and Barcelona participated in this study.
Ref.:Pla-Rabés, M.G. Matias, V. Gonçalves, D. Vázquez Loureiro, H. Marques, R. Bao, T. Buchaca, A. Hernández, S. Giralt, A. Sáez, G.L. Simpson, S. Nogué y P.M. Raposeiro. (2024) Global warming triggers abrupt regime shifts in island lake ecosystems in the Azores Archipelago. Communications earth & environment. DOI: https://doi.org/10.1038/s43247-024-01744-6
L'entrada The lakes of the Azores: at a point of no return due to climate change ha aparegut primer a CEAB.