Sep 5, 2020 - Science

Forensic botanists say plants might one day detect bodies

A photo of trees.
Photo: Andrew Lichtenstein/Corbis via Getty Images

Human remains can be hidden by tree canopies and brush, but a team of forensic botanists is proposing plants might one day be used to actually find bodies.

Why it matters: At the end of 2019, there were almost 90,000 active or ongoing cases of missing people in the U.S. Finding people who disappear, which is crucial for closure and justice, can be difficult in forests because of the terrain, vast search areas and dense vegetation.

How it works: When bodies begin to decompose, microbes, minerals and metals enter the soil, where they can be taken up by nearby plants, changing the wavelength of light reflected by their leaves.

  • Remains release nitrogen — pounds of it in the case of a human body — that causes more chlorophyll to be produced by plants, creating a "greening effect."
  • How fast those changes may appear and whether they can be detected with drones is being investigated by researchers at the University of Tennessee, Knoxville's Anthropological Research Lab — also known as the Body Farm.
  • Another possible signature: cadmium, which is present in small amounts in the soil and large ones in people who smoke or work in certain areas of manufacturing.
  • It too changes the spectral properties of leaves and thus "provides a reasonable target for identifying clandestine graves," plant biologist Neal Stewart and his anthropologist and soil scientist colleagues write in the journal Trends in Plant Science this week.

What's next: The field project to try to determine and detect the plant signatures began in June, and Stewart anticipates one limitation may be finding signals that are specific to humans versus deer or other large mammals.

  • Even still, the approach might be used to at least quickly narrow search-and-rescue efforts, he says.
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