Satellites can spy the menace of invasive flowers in West Africa

Sometimes, flowers can be the villain. Water hyacinths, with their seemingly harmless violet petals and lush green leaves, have invaded tropical parts of Central Africa, including Benin. In Lake Nokoué in Cotonou, near the country’s populous central coast, the hyacinths threaten to take over. In the last few decades, they have spread into dense colonies that block sunlight, crowd out native plants and wildlife, clog the waterways and irrigation canals, and hinder villagers as they try to travel and collect fish.

Danielle Wood thought that space technology could be part of the solution. In 2017, soon after moving from a job at NASA to MIT, she attended a conference where she encountered a Beninese entrepreneur who invited her to visit and explore how satellite data could help local groups manage the invasive weeds. Today Wood is the director of the Space Enabled research group at MIT’s Media Lab, and she was part of a team that just published their findings in the journal Frontiers in Climate, showing how Earth observation technologies can map and monitor hard-to-reach areas to inform local decisionmaking, specifically on how Beninese groups are tackling the hyacinth problem with data from satellites, drones, and sensors in the lake.

Ufuoma Ovienmhada, a PhD student in Wood’s group, led the project and worked with Fohla Mouftaou, a Beninese doctor and managing director of the company Green Keeper Africa. Mouftaou does not want to get rid of the water hyacinths, which originate in the Amazon basin in Latin America, he would rather make better use of them in his community. The flowers can actually be transformed into an organic fiber that is effective at absorbing oil-based pollutants and can be used to clean up oil spills or surfaces contaminated with oil, acids, and paints. Green Keeper Africa hires hundreds of people in the area, including women who live near the lake, to gather the hyacinths and make them into the fiber. First, however, they need to know where to focus their harvesting efforts. 

Ovienmhada had flown a drone quadcopter over and around the lake to collect high-resolution photos of where and how fast the hyacinths are growing, but she was limited by where she could pilot it and how long the batteries lasted. Satellite data was more comprehensive. The team collected images of the whole region in visible and near-infrared wavelengths, as well as radar data with radio and microwaves. Then she compared it to NASA orbital images going back to 1980. “The really cool thing about satellite data, compared to other methods, is that satellite data is large-scale and has a long historical archive of imagery. We were able to analyze trends in water hyacinth growth,” Ovienmhada says.

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