On the western edge of Africa, in Senegal, Cornell and global researchers are advancing ways to control a fast-growing, invasive and disease-carrying aquatic plant with agricultural solutions.

This plan calls for physically removing the aquatic plants – the preferred host of snails that ferry flatworms harboring the disease, Schistosomiasis – and turning the flora into inexpensive compost or livestock feed. 

“We’ve demonstrated in small-scale, researcher-managed trials that we can reduce disease vectors, get people healthy and boost agricultural productivity,” said Chris Barrett, the Stephen B. and Janice G. Ashley Professor of Applied Economics and Management in the Cornell SC Johnson College of Business and professor in the Jeb E. Brooks School of Public Policy. “The next challenge is to commercially scale this work and sustain it economically.”

The Cornell 2030 Project climate initiative has provided $150,000 for Barrett and Ying Sun, associate professor in the School of Integrative Plant Science Soil and Crop Sciences Section (College of Agriculture and Life Sciences) to scale up.

The cycle of disease the Senegalese face and subsequent economic hardship begins with the freshwater plant hornwort (Ceratophyllum demersum), known locally as “nianthie,” which resembles brilliant green, underwater feathers. This invasive vegetation proliferates in rivers, lakes and irrigation canals, partly due to fertilizer runoff from nearby farms and it is then aggravated by climate change. Snails that carry Schistosoma parasites live in hornwort.

“These infectious worms live in water bodies, carried by snails that need a place to live and a place to eat,” Barrett said. “If we remove the submerged plants, we remove the snail’s home and the snails largely disappear. And when the snails disappear where people enter the water, then people stop getting infected.”

These parasitic Schistosoma flatworms (flukes) easily creep into the human body if people swim, fish or do laundry in an infested water body, according to the World Health Organization. The adult worms will reside in human blood vessels, and when the females release eggs, larvae can become trapped in body tissues and damage organs. The disease affects 240 million people globally.

Jason Rohr, professor of ecology and public health at the University of Notre Dame, led a global group of biological, medical and social scientists – including Barrett and Molly Doruska, a doctoral student in the field of applied economics and management – who published research in Nature (July 2023) to show how to slow the disease and benefit the Senegalese economy.

“We’re examining how any Senegalese engineering company that has backhoes or front-end loaders – which might normally work on roads – can make money on regular, larger-scale, mechanical removal of these plants,” said Barrett, a Cornell Atkinson Center for Sustainability senior faculty fellow.

Scouting for the submerged plants is labor intensive. Sun, a Cornell Atkinson faculty fellow with expertise in remote sensing, examines how to employ satellite imagery to identify where submerged hornwort vegetation is located. 

Satellite images provide many spectral measurements – such as in the near-infrared and red-edge band, in addition to the red-blue-green part of the electromagnetic spectrum – to differentiate vegetation, Sun said.

By using these images, Sun's group will produce a weekly map of submerged vegetation on a national Senegal level, so that a Senegalese business can determine if there are enough plants to harvest profitably. 

“Conventional approaches, field samples or collecting drone images are time-consuming and cost-prohibitive to implement at a national scale,” Ying said. “Satellite imageries are the only way to provide low-to-free cost, real-time mapping of submerged vegetation, at a country scale and beyond.”

The 2023 Nature paper established this project’s economic viability for the villages and nearby small-holder farms. The authors found that more than 80% of households in the Senegal River valley had been affected by Schistosomiasis in the past. 

Earlier this year, Barrett and Doruska’s team taught villagers how compost could boost crop production. They explained that by removing aquatic vegetation, Schistosomiasis infections are greatly reduced.

Doruska surveyed villagers to gauge their understanding of Schistosomiasis and how – in an agrarian society – they may value compost or feed made from aquatic vegetation. She used experimental auctions to discern villager willingness to pay for compost or feed.

“In each village, after educating people, we ran four experimental auctions,” Doruska said. “We varied the information before the auction to grasp how participants valued goods, and then we asked them how much they’d pay for a bag of compost or animal feed.”

The economists achieved their goal: The villagers bought the inexpensive by-products.

In late May, the Ecological Society of America gave their annual Sustainability Science Award to the group that published in Nature.

The Senegalese government’s effort to improve agricultural productivity through fertilizer subsidies had an unintended consequence that aggravated disease, Barrett said. 

“Now, we are changing a nutrient cycle to advance agricultural productivity, improve family incomes by having people sick less often and less severely and having children in the villages stay in school. We’re changing the economic cycle and closing the nutrient loop, with favorable human health consequences.”

In addition to the University of Notre Dame, Senegalese project partners are research groups Station d’Innovation Aquacole, the Centre de Recherche Biomédicale Espoir Pour La Santé and Université Gaston Berger, all in the Saint-Louis region. Partners also include the Centre de Recherche pour le Développement Economique et Social (CRDES) and the Université Cheikh Anta Diop, both based in Dakar, Senegal.