A sweeping new analysis of 150 years of botanical records has revealed that moss may be one of the most powerful and overlooked forensic tools available to investigators. Because different moss species thrive in extremely specific micro-environments — defined by precise combinations of temperature, humidity, light exposure, soil chemistry, and substrate type — even a single fragment too small to identify with the naked eye can be traced back to a specific type of habitat with striking accuracy.
The study, published in Forensic Science International, used machine learning trained on over 3,000 georeferenced moss samples to match fragments to habitat profiles with 94% accuracy. When geographic data was included, the accuracy rose further, allowing researchers to narrow the likely collection site to within a few kilometers.
Moss Goes Where People Go
"Moss clings tenaciously to shoes, clothing, vehicle tyres, and tool handles," said Dr. Helen Muir of the Royal Botanic Gardens, Kew, who led the research. "If you walk through a particular forest, cave system, garden, or riverbank, you carry an invisible botanical record of that visit. It transfers to surfaces you touch, and it persists remarkably well because moss desiccates rather than rots."
Forensic botanists have long used pollen, seeds, and leaf fragments as evidence. Moss has been largely ignored because of the difficulty of identifying species from small fragments. The AI-assisted approach resolves this by simultaneously analyzing chemical composition, cell wall structure, and spore morphology.