human activities

More than 100 shallow lakes stretching over 1,000 kilometers along the Atlantic coast of southern Brazil and Uruguay could become one of the world’s most important natural laboratories for understanding how climate change and human activities reshape freshwater ecosystems.

An international team of researchers reports that these largely overlooked subtropical lakes offer an unparalleled opportunity to monitor biodiversity, water quality, pollution, and ecosystem resilience in a rapidly changing world.

Published in One Ecosystem, the study is the first comprehensive assessment of the Southern American Coastal Shallow Subtropical Lakes, highlighting their global scientific importance and outlining a roadmap for long-term international monitoring.

The Tramandaí Lagoon estuary, located between the municipalities of Imbé (left side of the channel) and Tramandaí (right side of the channel) in Rio Grande do Sul, Brazil, connects a complex of more than 40 coastal lakes to the Atlantic Ocean. Credit: CECLIMAR Collection (Photo credit: Acervo CECLIMAR).

“Most of what we know about lakes comes from the Northern Hemisphere,” says lead author Mariana Kluge of the Swedish University of Agricultural Sciences (SLU).

These subtropical lakes fill a major gap in global freshwater research. They allow us to test ecological theories under very different environmental conditions while providing crucial insights into how subtropical freshwater ecosystems respond to climate change and increasing human pressures.
adds Prof. Renata Medina-Silva of Pontifical Catholic University of Rio Grande do Sul (PUCRS)

The lake network forms one of the largest continuous coastal shallow-lake systems on Earth. Despite its extraordinary size and diversity, it has received far less scientific attention than well-known freshwater systems elsewhere in the world. Yet the region is already experiencing many of the environmental challenges, expected to intensify in the coming decades – including a direct impact of the El Niño Southern Oscillation – alongside heavy urbanisation, which has driven eutrophication, agricultural and wastewater pollution, emerging contaminants such as pharmaceuticals and microplastics, and increasingly frequent extreme rainfall and flooding events.

Coastal lakes from South America — Overview of the environmental heterogeneity found across South America’s unique coastal lake systems. Credit: Kluge et al., 2026.

Christian Wurzbacher of the Technical University of Munich argues that these lakes can serve as “sentinel ecosystems“- natural observatories that reveal early signs of environmental change. By combining microbial ecology, environmental DNA, remote sensing, water chemistry, and long-term ecological monitoring, scientists hope to develop new indicators capable of detecting ecosystem stress before irreversible damage occurs.

Our vision is to establish an internationally coordinated monitoring network that not only benefits South America, but also improves our understanding of freshwater ecosystems worldwide. The microbial communities living in these lakes can act as highly sensitive biological sensors, helping us identify pollution, ecosystem degradation, and even emerging public health risks.
says Prof. Haig of the Federal University of Rio Grande do Sul (UFRGS).

lakes in South America — Despite their high ecological value, these lakes are under increasing pressure from eutrophication, urban growth, and competing human uses such as water supply, irrigation, navigation, fishing, recreation, and sewage disposal. Credit: Kluge et al., 2026.

The publication emerged from an international workshop held at two universities – PUCRS and UFRGS – in Porto Alegre, Southern Brazil, bringing together researchers from Brazil, Uruguay, Germany, and Sweden to define future research priorities. The team identified four representative large-scale lake regions that together capture the broad environmental gradients across the system and offer ideal sites for coordinated long-term observation.

As climate change accelerates and pressures on freshwater resources continue to grow, the researchers believe that protecting and studying these remarkable lake systems will generate knowledge extending far beyond South America – informing global strategies for safeguarding biodiversity, improving water management, and strengthening resilience to environmental change.

Original source:

Kluge M, Shubeita A, Uchaikina A, Alonso C, Herrman B, Menegotto-Silva C, Lopes C, Pagani D, Marques D, Moreira-Silva E, Kristiansson E, Quintana I, Cavalcanti J, Fleck J, Ribeiro K, Varghaei L, Oliveira L, Rodrigues LR, Ramilo L, Crossetti L, Stockenreiter M, Cabezudo M, Lima M, Gonçalves NP, Mazzeo N, Schneider R, Utz LP, Bertilsson S, Wurzbacher C, They NH, Medina-Silva R (2026) Coastal subtropical Southern American shallow lakes as unique ecosystems for monitoring anthropogenic induced ecosystem changes. One Ecosystem 11: e186107. https://doi.org/10.3897/oneeco.11.e186107

Two juveniles of Shiny Cowbird, a parasitic bird that lays its eggs in the nests of other birds, were spotted in the Andean city of Quito, Ecuador, for the first time. This finding represents an altitudinal expansion of approximately 500 m.

Breeding populations might have been prompted by forest fragmentation and/or climate change, suggest the research team, led by Dr Verónica Crespo-Pérez, professor at Pontificia Universidad Católica del Ecuador (PUCE). Resultingly, the ‘immigrants’ could be threatening native birds. The study is published in the open access Biodiversity Data Journal.

“The Shiny Cowbird is native to the lowlands of South America but within the last 100 years, it has been expanding its distribution to higher altitudes and latitudes” says the lead author.

The bird had already been noted from high altitudes in Bolivia and Perú, and in some localities in the Ecuadorian Andes. Since 2000, Juan Manuel Carrión, co-author and director of the Zoo in Quito, recalls observing Shiny cowbirds near his home in a valley near Quito at 2,300 m above sea level (asl). However, one has never before been reported from an altitude as high as 2,800 m asl.

Moreover, the fact that the observed individuals were juveniles means that the species is already breeding in the city.

“Such a significant expansion of reproductive birds, of approximately 500 m, could be related to human disturbances, like forest fragmentation or climate change,” adds Crespo-Pérez.

The observations took place at the PUCE campus about a year ago. Two juvenile Shiny cowbirds were seen parasitizing two different pairs of Rufous-collared Sparrow, one of the most common birds in Quito. The cowbirds displayed food-begging behaviors to adult sparrows, including chasing the sparrows on the ground and chanting intensely on bushes and tree branches.

“These observations mean that the birth mother of the cowbird laid her eggs in the nests of the sparrows, who inadvertently, became the cowbird’s foster parents and incubated, fed and cared for the it as if it were its own, even though the cowbird is almost twice as big,” says Miguel Pinto, co-author and professor at Escuela Politécnica Nacional, and former postdoctoral fellow at the Smithsonian Institution.

“The sparrows were not feeding fledglings of their own species, which suggests that the Cowbird could be having some negative effect on the Sparrow, at least on their ability to reproduce,” points out Tjitte de Vries, co-author and professor at PUCE.

There are several published reports of negative effects of Cowbirds on other birds, especially on species that are already endangered or have restricted distribution ranges. Therefore, this report of an expansion of the Shiny Cowbird towards higher altitudes may be of concern, mainly for native, endemic or endangered bird species.

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Original source:

Crespo-Pérez V, Pinto C, Carrión J, Jarrín E R, Poveda C, de Vries T (2016) The Shiny Cowbird, Molothrus bonariensis (Gmelin, 1789) (Aves: Icteridae), at 2,800 m asl in Quito, Ecuador.Biodiversity Data Journal 4: e8184. doi: 10.3897/BDJ.4.e8184

Tag: human activities

Hidden Freshwater Giants Could Become The World’s Next Climate Observatories

New immigrant: Shiny Cowbirds noted from a recording altitude of 2,800 m in Ecuador