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We invite you to note what you are seeing around you in your own part of the world, and to share your observations in the comments below.
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Who doesn’t love a detective story? Patricia Wiltshire reveals how she helps to solve crimes in The Nature of Life and Death, Tales of a Forensic Ecologist. Wiltshire defines the scope of forensic ecology as including botany, palynology, mycology, bacteriology, entomology, parasitology, human/animal/plant anatomy, soil and sediment science, statistics, and more. With all that expertise, we’re lucky she’s on our side of the law!
Q: What is the maximum distance most people are willing to lug a body? (answer below)
We pay little attention to the pollen, fungal spores, and other subtle traces we pick up on and in our clothing, shoes, hair, skin and nasal cavities, not to mention our autos, but a trained observer can use these to learn a lot about where we have been. Pollen profiles are so strongly local that assemblages ten yards apart can be very different. And, pollen is durable. “If the activity of bacteria and fungi is suppressed by lack of oxygen, or by acidity, pollen can remain preserved for thousands of years.” It has been extracted from Otzi the Iceman’s gut, from the dung of woolly mammoths, and from a fossilized, Cretaceous bee.
Fun fact: Pollen carries a negative charge. Bees carry a positive charge.
Patricia Wiltshire is English. The landscapes she describes and most of the plants pertain to England, but the principles apply everywhere. There is nothing straight forward about interpreting pollen and spore samples. Pollen of related plants may be indistinguishable. For example, rose family plants (at least those in England) fall into two categories: pollen of bramble, rose and hawthorn flowers look alike, while pollen of blackthorn, plum and cherry form another uniform group. It is easy to tell which group is present, but which member of the group cannot be determined from pollen shape.
The volume of any particular pollen type present in a site or sample may not be at all proportional to the number of plants that produced it. Bee-pollinated plants need only produce very sparing amounts of pollen, because bees are so efficient at moving it to the target plants. Wind-pollinated plants, like grasses and many trees, churn out masses of pollen because moving air is so hit-or-miss in delivery. But, sparse pollen can be useful forensically; if it fails to get into the air, its presence can indicate direct contact with the plant.
Secondary traces are also informative. Primrose (Primula vulgaris) produces very little pollen, but a companion fungus, which grows only on primrose leaves, makes lots of spores and is thus diagnostic for the presence of primroses.
But the most interesting aspect of Wiltshire’s work involves the way she pulls together all the trace evidence to visualize an unknown site. She has a prodigious, detailed understanding of her regional plant distribution. Willow and alder pollen suggest damper soils. Clematis suggests alkaline soils, rhododendrons indicate acidic conditions. Certain combinations are likely to come from mature hedgerows, some from beech woods, others from hay meadows.
Fun fact: Coal soot from an old chimney contained the pollen characteristic of a hay meadow. Wiltshire realized that the coal had been delivered by horse cart, contaminated by the dust of horse dung, which still contained pollen from hay.
Wiltshire’s book illustrates some remarkable detective work. This Sherwood Sherlock offers details about her exacting procedures and her collaborations with other experts.
Finally, the answer you’ve been waiting for: most people will not lug a body farther than 100 meters. More than that makes you an over-achiever.
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