If you thought a “pet detective” was an improbable basis for films, how about plant detectives? Yet botanists think their field could help us recover dead bodies, possibly solving murders in the process. Although it is yet to happen, Professor Neal Stewart of the University of Tennessee hopes the work he has done in this direction will eventually bear fruit.
“In smaller, open landscapes foot patrols could be effective to find someone missing, but in more forested or treacherous parts of the world like the Amazon, that's not going to be possible at all," Stewart said in a statement. Forests, where people are more likely to get lost or murderers seek to hide evidence, are a different matter.
"This led us to look into plants as indicators of human decomposition, which could lead to faster, and possibly safer body recovery," Stewart said.
The University of Tennessee already has a “body farm” where forensic scientists study decay under varying conditions in the hope of replicating the precision TV crime shows portray. Stewart realized studying a body’s effects on the surrounding soil might offer a stepping stone to finding the effects on plants growing there. After all, sensors carried on satellites and airplanes can use the color of leaves in a patch of forest to test for water stress – might the human body’s contents produce something similar?
"The most obvious result ... would be a large release of nitrogen into the soil, especially in the summertime when decomposition is happening so fast,” Stewart said. Plants fed a high-nitrogen diet produce more chlorophyll and therefore have greener leaves. The average American contains 50 times the nitrogen recommended to fertilize temperate trees, he notes in Trends in Plant Science.
Stewart and co-authors have begun the process of studying the spectra of light reflected off plants growing at the body farm to see if there are noticeable differences based on how close they are to bodies. What may prove harder is distinguishing daisies pushed up by a human from those fertilized by a large animal.
Nevertheless, Stewart doesn't think it's an insuperable problem. On the basis “you are what you eat,” humans are rather different nutritionally from any other animal, and the difference is wider for most of us today than our ancestors. If searchers know something about the individual – Stewart gives the example of a heavy smoker or someone taking known medication – it might be even easier to track their molecular residue in the plants that grow over their bodies.
Stewart also proposes that certain plants, particularly invasive species, may be more likely to flourish where a human has died.
Even if these indicators are not precise enough to detect the place where someone has died from a single fly-over, Stewart hopes it will one day be possible to identify the most likely spots to find a body from the air. These could then be checked using more conventional means.