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Tropical ecosystems at risk: The critical role of aquatic insects

Tropical ecosystems are significantly dependent on emerging aquatic insects, which could expose them to greater risks, according to a new study led by researchers from Queen Mary University of London.

Published in the journal Ecology Letters, the study is the first to directly analyze and compare the interconnectedness between land and water in tropical and temperate environments through the lens of aquatic insects.

Focus of the study

The study was focused on English, Welsh, and Scottish forests as well as Amazonian and Atlantic rainforests in Brazil. 

The researchers used stable isotope analysis to trace signals of aquatic prey within the tissues of arthropod predators, such as spiders. This technique illuminated the predators’ dietary patterns away from water bodies.

What the researchers learned

Notably, spiders in tropical locales exhibited higher consumption of aquatic insects compared to their UK counterparts. Such dietary diversity indicates that terrestrial fauna in the tropics heavily relies on aquatic insects. 

According to the researchers, these results suggest that tropical environments are more vulnerable to future disruption to the interconnections between land and water. 

Increasing pressures 

“Our findings show that we cannot simply apply knowledge from research in temperate zones to protect tropical ecosystems,” said study senior author Dr. Pavel Kratina. 

“That tropical ecosystems are more vulnerable to disruptions to the links between land and water is worrying considering the increasing human pressures on tropical freshwater ecosystems, which are among the most threatened in the world.”

Negative human impacts

Emerging aquatic insects serve as pathways through which negative human impacts can travel from aquatic to terrestrial environments. 

Activities that diminish insect populations, like stream pollution, inadvertently affect land-based predators by limiting their access to essential nutrition derived from insects. 

Given that tropical aquatic insects are perilously declining due to human endeavors and climate shifts, the study forewarns of consequential ripple effects throughout tropical regions.

Riparian buffers 

The study highlights the urgent need for robust protection measures for “riparian buffers,” or safeguarded land strips surrounding waterways that are crucial for maintaining the land-water connections. 

Present buffer dimensions, ranging between 5 to 100 meters, are deemed insufficient to protect vast terrestrial biodiversity around water bodies. 

With buffer regulations in Brazil having been eased in recent years, the researchers advocate for enhanced protection policies for these buffers and a more integrated approach considering the interconnectivity between different ecosystems, especially in tropical areas.

Study challenges

“Our research took us to remote parts of the world from the Amazon jungle and Iguaçu River basin in Brazil to Snowdonia national park in Wales and The Trossachs in Scotland,” said study lead author Dr. Liam Nash.

“We braved ticks, wasps, midges, and snakes to collect our samples, and saw animals such as harpy eagles and tapirs along the way. We ran into challenges with the pandemic, which saw me having to fly out of Brazil on one of the last available flights in March 2020 as travel rules were changing hourly! This work could not have happened without the help of experienced local field guides and close collaboration with scientists and students from Brazil.”

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