Tropical insects are more sensitive to climate change than expected

Insects that are adapted to wet, tropical regions will be impacted by the drier conditions associated with climate change. A paper recently published in Global Change Biology reveals that tropical insects will also be affected by relatively heavy rainfall. 

Researchers in Peru conducted a five-year study on the effects of short-term droughts followed by increased precipitation and found a 50 percent decline in the biomass of arthropods (spiders and insects). These findings suggest that arthropods are more sensitive to climate change than previously thought. 

“Most of the time when we think about climate change, we think about warming temperatures, but rainfall patterns will change as well, which is something insects seem to be especially sensitive to,” said Felicity Newell, a postdoctoral associate at the Florida Museum of Natural History. “We’re seeing that rainfall extremes can have negative effects over very short timescales.”

This phenomenon of just the right amount of water is an example of Goldilocks preference. Insects, in particular, are already suffering assaults on many fronts, and now we know climate change is another serious threat to their populations. This data is especially alarming because over half of the world’s insect diversity occurs in the tropics. 

For part of the study, Newell and co-author Ian Ausprey compared rainfall and temperature measurements to the number of insects they collected in the Andes mountains of northern Peru for two-and-a-half years. While they expected that plant growth would determine insect abundance, they found that rainfall had the biggest influence. 

“Arthropod biomass decreased after three months of dry weather, but it also decreased after three months of exceptionally wet conditions,” Newell explained. “Biomass peaked at intermediate rainfall, creating a dynamic balance between too wet and too dry.” 

Although the researchers determined that tropical insects, especially smaller ones, were vulnerable to dry conditions in an experimental study, they could not determine why they also reacted negatively to very wet environments. 

Moreover, the predictive model they developed places insects as canaries in the coal mine since it predicts that insects will be the first type of animals to react to a climate in peril. Whatever the case, insects are indispensable. Many ecosystems depend on them as engineers, pollinators, and food sources. 

“Insects are incredibly diverse and important,” said Newell. “They fill the ecosystem roles of pollination and decomposition, and they serve as a food resource for many birds and mammals.” 

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By Erin Moody , Earth.com Staff Writer