Law enforcement receives numerous reports of people ‘disappearing’ in the forest, but surveys, aerial footage and dog teams are limited in their abilities of locating human bodies.
Now, forensic botanists are investigation how plants show signs of nearby remains, as decomposing bodies release compounds in the surrounding environment.
These compounds can change soil composition that in turn alter the look of plants such as leaf color and reflectance.
The team believes studying levels of nitrogen in an area could lead officials to a body, along with the adoption of unmanned aerial vehicles to detect elevation changes as unmarked graves settle over time.
Forensic botanists are investigation how plants show signs of nearby remains, as decomposing bodies release compounds in the surrounding environment. These compounds can change soil composition that in turn alter the look of plants such as leaf color and reflectance
The proposal comes from a team from the University of Tennessee, which is set to investigate how plants can lead to human remains at the college’s ‘body farm.’
Officially known as the Anthropology Research Facility, this is where scientists examine the process of human body decay under different conditions.
The team will determine how ‘cadaver decomposition islands’ – the zone immediately surrounding humans remains- change the nutrient concentrations of the soil, and how those changes manifest in the nearby plants.
Senior author Neal Stewart Jr., a professor of plant sciences at the University of Tennessee, said: ‘The most obvious result of the islands would be a large release of nitrogen into the soil, especially in the summertime when decomposition is happening so fast.’
The team will determine how ‘cadaver decomposition islands’ – the zone immediately surrounding humans remains- change the nutrient concentrations of the soil, and how those changes manifest in the nearby plants Once diagnostic spectra are compiled, researchers can begin to think about scaling up to drones
‘Depending on how quickly the plants respond to the influx of nitrogen, it may cause changes in leaf color and reflectance.’
The study, published in Cell Press, notes that as a human body begins to decompose, it flushes out nutrients that alter the surrounding landscape and vegetation – specifically nitrogen.
‘The average-sized human from the USA contains 2.6 kg nitrogen, much of which will be converted to ammonium during the course of decomposition,’ reads the study.
‘If we consider the human decomposition island to be approximately 3 m2 , the amount of added nitrogen to the rhizosphere is approximately 50 times greater than the recommended seasonal nitrogen fertilizer rate for home shrubs and trees in the temperate USA.’
On the other hand, when larger mammals die, their bodies also release nitrogen.
The team said the key is finding metabolites specific to the breakdown of humans, which could include prescription drugs or food preservatives – all of which can impact vegetation.
‘One thought is if we had a specific person who went missing who was, let’s say, a heavy smoker, they could have a chemical profile that could trigger some sort of unique plant response making them easier to locate,’ said Stewart.
‘Though at this stage this idea is still farfetched.’
The study provides an example of searching for high levels of cadmium, a soft, silvery-white metal, which could be used to find someone who worked in manufacturing or event smoked cigarettes.
Experts understand that they must first unravel the influences of cadaver metabolites on plants, but once they crack the code, search teams can use these clues to scan plants for specific fluorescence or reflectance signals that indicate human remains are close by (stock)
Plants are found to easily ingest the chemical and scientists have used this to determine polluted areas along highways.
And the changes can be observed in leaves of the vegetation.
Stewart and his team understand that they must first unravel the influences of cadaver metabolites on plants, but once they crack the code, search teams can use these clues to scan plants for specific fluorescence or reflectance signals that indicate human remains are close by.
‘We’ve actually built a whole plant imager that can analyze fluorescence signatures,’ said Stewart.
‘But the first steps are going to be very fine scale, looking at individual leaves and measuring how their reflectance or fluorescence changes over time when plants are near human remains.’
Once diagnostic spectra are compiled, researchers can begin to think about scaling up to drones and other technology to investigate wide stretches of area in a short time.
‘When you start to think about deploying drones to look for specific emissions, now we can think of the signals more like a check engine light– if we can quickly fly where someone may have gone missing and collect data over tens or even hundreds of square kilometers, then we’d know the best spots to send in a search team,’ Stewart explained.
‘While these ideas are exciting, we are still several years away from feasibly using plants as search tools in body recovery missions.
‘In the meantime, a collaborative team of botanists, anthropologists, and soil scientists will begin working at the body farm, designing their first set of plant-cadaver experiments.’