Tracking a Deadly Rise, Historic Fall of Insect Populations

An estimated 10 quintillion insects are on the planet, a staggering number that is at the center of a data crisis for entomologists. Researchers are struggling to understand historic shifts taking place among insect populations amid climate change and other environmental threats, from deforestation to pesticide use.

Nearly 40% of all insect species are declining globally, while a third of them are now considered endangered. And yet, some deadly populations are on the rise.

Associate Professor of Physics Benjamin Thomas is developing new laser-based instruments to better study what is occurring among the world’s most diverse animal population, which accounts for roughly half of Earth’s animal biomass today.

“Because of their size and great diversity, it’s been difficult to collect data on insect populations to the point that entomologists talk about a data crisis in their field,” says Thomas. “Population trends we do have show great variance between insect families or groups and regions. For example, terrestrial insects seem to be more at risk of joining this insect decline than freshwater insects, which are increasing in some cases as climate conditions grow warmer and wetter.

“We are developing optical sensors to monitor our environment and provide better data to understand the situation. The goal is a diagnostic tool that can be widely deployed for surveying insect populations autonomously.”

With funding from the National Institutes of Health, Thomas has been establishing such a tool to track the planet’s most dangerous animal, responsible for over a half a million human deaths each year — mosquitoes.

For the past four years, he has been collaborating with the Hudson Regional Health Commission’s mosquito control program in Secaucus, N.J., where he is deploying his sensors.

His approach employs a scanning technology found in newer smartphones, LiDAR, which involves a laser wavelength in the near-infrared spectral range that is invisible to insects.

“We are sending a laser beam across open fields more than 50 meters, about 2 inches in diameter and about a foot above the ground. When insects fly through the beam, our optical receiver measures the backscattered light,” explains Thomas. “By studying those optical signals, we retrieve a lot of information on any insect entering the beam, such as its wingbeat frequency, wing and body size, unique wing movements and more.”

Thomas says his instruments registered more than a million insect observations last mosquito season, from April to October.

These observations could help Hudson County health officials track the abundance of deadly populations such as the mosquito species Culex, for example, which brought West Nile Virus to Queens, N.Y. nearly 20 years ago and is growing in the New York City-Metropolitan region today.

Specifically, Thomas is tracking unique light signatures produced by females, which unlike males, can transmit disease using mouthparts capable of puncturing human skin.

“Females average 350 wing beats per second, compared to males at 500 a second,” says Thomas. “The instrument has a temporal resolution down to the minute so not only can we track population density over the season and potentially over years, but we can look at the behavior and peak of activities of groups each day.”

“While still being developed, I believe this technology will offer several advantages over traditional methods of adult mosquito surveillance,” says Gregory Williams, Superintendent of Mosquito Control at Hudson Regional Health Commission. “It will reduce the turnaround time for gathering data from the field, allow us to track the impact of our insecticides on non-target species and eliminate the sampling biases inherent in our current mosquito traps. Even now, the current systems could be an excellent early-detection tool for invasive species or for monitoring specific disease vector species.”

Beyond tracking mosquito populations, Thomas says his research may give scientists much-needed data insights into insects in rapid decline, such as bees and other pollinators.

“What we do with mosquitoes can be done with pollinators, though it’ll take more instruments and continuous effort,” says Thomas. “We can identify them using a machine learning classifier we’ve been refining since we began working with mosquitoes … we first collect species data in the lab to train our models, allowing us to then identify and track activity of these insects in the wild.”

The work could be of significance to preserving vital agricultural landscapes — roughly 35% of the world’s food crops depend on pollinators to reproduce, according to the Food and Agriculture Organization of the United Nations.

Thomas plans to study pollinators locally in Secaucus and Newark, eventually scaling up to cover regions of rich wildlife such as New Jersey’s wetlands, to track how pollinator populations evolve over years.

“We started making measurements on species of wild bees in the lab already so we can more accurately identify them in the field,” says Thomas. “We think our observations can offer important new data on their peak of activity and behavior as it relates to weather and temperature, and hopefully, we can eventually begin to study things such as the impact of pesticides on pollinators, which may inform new strategies for protecting them.”

Captions: Benjamin Thomas used LiDAR in Secaucus, N.J., to survey mosquito populations.

SIDEBAR:

Paying Mother Nature a Fair Wage

As communities debate the merits of preserving, developing or restoring natural features in the landscape, Zeyuan Qiu,a professor of environmentalscience and policy, is helping themplace a monetary value on thecontributions of forests, streams and meadows.

“Despite being so essential, ecosystem services, the benefits that human society receives from nature, are not commercial products that are properly priced in a marketplace. Most ecosystem services are free gifts of nature and, therefore, are often overused and underappreciated because of the lack of a price tag,” he notes. “If we’re to preserve our natural capital, we need to provide the evidence for it in common measurements people can understand and appreciate.”

In 2021, Qiu and NJIT students volunteered with the Princeton Environmental Commission to determine the value of maintaining old-growth forests in the town. Among other calculations, they estimated contributions to carbon sequestration, oxygen production, carbon storage, water retention, air pollution removal and assigned these contributions a monetary value. The figure, which has not been published, helped guide the decision to preserve a 153-acre old-growth forest, protecting the land of over 10,000 trees from a proposed housing development.

“Old-growth forests like that are very rare and integral to an area’s natural heritage,” Qiu says. “They provide recreation and other benefits for people and habitat for some unique plants and animals, including a species of frog found only in New Jersey.”

He is currently collaborating with colleagues at Rutgers University to develop a watershed restoration plan to reduce pollution loads to Barnegat Bay-Little Egg Harbor streams and improve the health of Southern Barnegat Bay. He is also working with the New Jersey Sea Grant Consortium to develop a national strategy for deploying green infrastructure and low impact development techniques to mitigate runoff and pollution impacts on freshwater systems. These include natural and man-made features, such as cisterns, rain gardens and riparian buffers, among others, that mimic nature’s functions.

“Given the extent of human disruption on natural landscapes through intensive urbanization and agriculture,” he notes, “there is also plenty of repair and design work to do.”