The lakes of the Azores are at their limits due to climate change

2024-10-17 23:21:00

The increase in temperature caused by climate change is endangering the lake ecosystems of the Azores archipelago. These lakes, important for the population because they are water reserves, contribute to water regulation, tourist and recreational activities and are essential for preserving the biodiversity of the islands, are losing part of their biodiversity and their ability to provide these ecosystem services , as reported by the National Museum of Natural Sciences.

The researchers consider it “probable” that the changes detected in the archipelago’s lakes are also occurring in other lake ecosystems on the planet.

This is confirmed by the study carried out on the island of São Miguel where they verified how the quantity of diatom species-unicellular algae that are at the base of the food chain-, have decreased by 27% in all lakes on the island since 1982, when the temperature in the northern hemisphere increased by 0.35ºC compared to the 20th century average. The researchers consider it “probable” that the changes detected in the archipelago’s lakes are also occurring in other lake ecosystems on the planet.

Diatom biodiversity declines

Declines in diatom biodiversity have occurred in the past, but they occurred in specific lakes that recovered quickly, now the loss of species is happening across the island. “The most serious thing about these data is not the almost 30% reduction in diatom species in one lake, but rather it is a decline that we have seen occurring on a regional scale across the island, which indicates that a homogenization,” warned Miguel Matías, researcher at the National Museum of Natural Sciences.

“Thanks to sedimentary documents that we have, which in some lakes date back four to five thousand years, we know that these declines in diatom diversity occurred in specific lakes due to environmental disturbances, but not across an entire island as is happening now. Furthermore, these were specific declines from which the ecosystem recovered easily,” the researcher continues.

According to the work, around 20,000 different species of diatoms are known and this is a group used as reference for knowing the environmental conditions of an ecosystemas well as to study climate changes that have occurred throughout the Earth’s history.

In 1982 a limit was exceeded, a point of no return, which homogenized the lakes at a regional level, implying a decrease in their ecosystem services.

Homogenization

“In the Azores, changes have already been observed in the communities of these algae since man began to expand in the archipelago and with this study we have verified that in 1982 a limit was exceeded, a point of no return, which homogenized the lakes at a regional level, which implies the decrease of its ecosystem services”, explained the researcher from the Autonomous University of Barcelona and the CREATE Sergi Pla-Rabés.

In 1982, when The temperature in the Northern Hemisphere increased by 0.35ºC Compared to the 20th century average, biodiversity has declined and ecosystems have become simpler and according to research published in the journal Nature Communications earth and environment (1), the set of anthropogenic disturbances of the ecosystem caused the development of phytoplankton made up of smaller algae and cyanobacteria, often accumulated on the surface, which They prevent sunlight from penetrating deeper areas of the body of water.

By decreasing the availability of light, the available habitat for benthic diatoms and the number of species are reduced, profoundly simplifying the ecosystem”, comments Vítor Gonçalves of the University of the Azores.

“Our hypothesis is that this homogenization that we documented on São Miguel Island is occurring in lake ecosystems of island areas and perhaps in isolated lake regions of the Northern Hemisphere and the planet,” says Sergi Pla-Rabés.

A Northern Hemisphere annual surface temperature anomaly (NHSTA) averaged from 1982 to 2011 compared to the 1901-1981 average, the black rectangle indicates the Azores archipelago. B Location of the lakes studied on the island of São Miguel. C Laghi studied 1 Azul, 2 Santiago, 3 Empadadas Norte, 4 Fogo and 5 Furnas.

Ecosystem restoration

With this data it is essential to increase ecological restoration processes that allow increasing environmental diversity throughout the island. “The degradation of ecosystems It’s not something that can be completely reversed.we cannot aspire to return to the environmental situation that existed in the past, as if there were no human populations on the islands,” warned researcher Pedro Raposeiro, also from the University of the Azores.

The team’s proposal to increase the complexity of ecosystems, thus ensuring the maintenance of ecosystem services necessary for the island population, is to reduce local pressures that can be controlled. “We believe it is necessary to concentrate efforts in certain points of the island that farms or infrastructures are kept outside lake basins. Ultimately, it is about practicing ecological restoration that takes into account the economic and social situation of those who live on the island”, concluded researcher from the University of the Azores, Vítor Gonçalves.

Research staff from the Autonomous University of Barcelona collaborated on this study (UAB), del CREATENational Museum of Natural Sciences (MNCN-CSIC), Geosciences Barcelona (GEO3BCN-CSIC), the Center for Advanced Studies of Blanes (CEAB-CSIC), and the Universities of the Azores, Évora, In Coruna Yes Barcelona.

References

• (1) Global warming causes abrupt regime changes in the island lake ecosystems of the Azores archipelago. Nature Communications earth and environment.