Tropical ecosystems are more reliant on emerging aquatic insects, making them more vulnerable to disruptions in the links between land and water, according to a new study by researchers from Queen Mary University of London and the University of Campinas in Brazil.
Illustration of the hierarchical, spatially nested sampling design, sampling 240 riparian arthropod communities from 48 streams in 7 sites across two ecosystem types: (a) four tropical rainforest sites in Brazil and (b) three temperate mixed broadleaf forest sites in the UK. Sampling was conducted at five distances along 150 m taken from 6 to 7 replicate streams within the same catchment at each site, e.g., (c) The Trossachs National Park, UK; (d) Iguacu National Park, Brazil; (e) Snowdonia National Park, UK; (f) Ashdown Forest, UK. Country maps coloured by ecoregion classification from Olson et al. (2001). Site maps were made using ArcGIS® software with the ‘Outdoor’ base-map by Esri©.
The study, published in the journal Ecology Letters, found that disturbances to aquatic-terrestrial linkages could have cascading consequences for tropical food webs. To safeguard these ecosystems, the study highlights the importance of protecting riparian buffers. This is the first study to directly compare the interconnections between land and water in tropical and temperate environments via the emergence of aquatic insects.
They found that the spiders were consuming more aquatic insect prey in the tropics than in the UK, resulting in higher overall dietary diversity in the tropical food-webs, on-land. Their results indicated that tropical terrestrial animals are more reliant on and impacted by emerging aquatic insects. This suggests tropical environments are more vulnerable to future disruption to the interconnections between land and water.
“Our findings show that we cannot simply apply knowledge from research in temperate zones to protect tropical ecosystems,” said Dr. Pavel Kratina, senior author of the study and Senior Lecturer in Ecology at Queen Mary University of London. “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.”
Emerging aquatic insects can become a pathway for negative human impacts to move from one environment to another. For example, polluting a stream may reduce insect numbers, which may in-turn reduce availability of nutritious food for land-based predators. Tropical aquatic insects are under threat of catastrophic declines because of human activity and climate change – the researchers’ results suggest this would have cascading consequences across tropical environments.