Tropical ecosystems more reliant on emerging aquatic insects, study finds, potentially putting them at greater risk

Comparing Tropical and Temperate Environments

The researchers utilized stable isotope analysis to trace the emergence of aquatic insects in English, Welsh, and Scottish forests, as well as in Brazil’s Amazonian and Atlantic rainforests. By examining the consumption of aquatic insect prey by spiders, they discovered that tropical spiders rely more heavily on aquatic insects compared to their counterparts in the UK. This results in higher dietary diversity within tropical food webs on land. The findings suggest that tropical terrestrial animals are more dependent on emerging aquatic insects and are therefore more susceptible to disruptions in the links between land and water.

The Vulnerability of Tropical Ecosystems

Dr. Pavel Kratina, senior author of the study and Senior Lecturer in Ecology at Queen Mary University of London, emphasizes the importance of recognizing the distinct vulnerabilities of tropical ecosystems. He states, “Our findings show that we cannot simply apply knowledge from research in temperate zones to protect tropical ecosystems. The fact that tropical ecosystems are more vulnerable to disruptions in the links between land and water is concerning, especially considering the increasing human pressures on tropical freshwater ecosystems, which are among the most threatened in the world.”

Cascading Consequences

The study highlights the potential for negative human impacts to spread from one environment to another through emerging aquatic insects. For instance, polluting a stream can lead to a decrease in insect numbers, subsequently reducing the availability of nutritious food for land-based predators. Given that tropical aquatic insects are already facing threats from human activity and climate change, the researchers’ findings suggest that these declines could have cascading consequences throughout tropical environments.

The Importance of Riparian Buffers

The researchers stress the need for greater protection of riparian buffers, which are strips of land around waterways that help maintain the links between land and water. Current buffer-strip sizes, typically ranging from 5 to 100 meters, are considered inadequate for protecting terrestrial biodiversity around water. In Brazil, regulations regarding buffers have even been relaxed in the past decade. The study emphasizes the necessity of broader consideration of ecosystem interconnections, rather than isolating different habitats, particularly in tropical regions.

A Challenging Journey

Lead author Dr. Liam Nash, recent PhD graduate from Dr. Kratina’s lab at Queen Mary, reflects on the challenges faced during the research. The team traveled to remote locations such as the Amazon jungle in Brazil and Snowdonia national park in Wales, encountering various obstacles including ticks, wasps, midges, and snakes. The COVID-19 pandemic also posed difficulties, with Dr. Nash having to leave Brazil on one of the last available flights in March 2020 due to changing travel rules. The success of the study was made possible through the assistance of experienced local field guides and close collaboration with scientists and students from Brazil.