Could a tree help find a decaying corpse nearby? | Hacker News Reader

Could a tree help find a decaying corpse nearby?

wired.com

49 pointsCyphase27 comments

> So Stewart and his colleagues set out in June to do exactly that. “Right now, for the Body Farm study,” says Stewart, “we're basically just taking the trees and shrubs that are growing naturally within our plots, then placing donors—as they refer to them—and then looking at leaf responses, plant responses, at various distances.”

Given that they’ve been putting bodies in these woods for decades now to study other things — and given that they presumably have records of where they put them — can’t they just do an analytical study of the effects of previous decomposition on current trees that grew near the placed corpses, rather than having to do an experiment on the scale of tree growth (= presumably years)?

Or is this all supposed to happen over a much shorter term than I’m imagining, such that you’d need to do an experiment to see the effects right away; and that a tree would be expected to revert to the mean in appearance after it runs out of human-type nutrients? (That’d kind of suck, since it would mean you wouldn’t be able to solve a missing-persons case that's been cold for decades this way — which is precisely the kind of case where you’d want to pull out this sort of technique. There are already good methods to find a body in the woods if they've only been missing for months/years, e.g. corpse-sniffing dogs.)

I guess the advantage over a dog is that, should it indeed have a detectable effect, and a sufficiently noticeable one, one could fly a drone (even, perhaps, a Global Hawk; I don't know how precise the pictures it takes are), and just scan huge swaths of forest at once, much faster than one could with even a hundred dogs.

But that's a lot of ifs.

I suspect the answer is no. Things are always dying and decaying in forests, and it seems like it would be hard to differentiate the affect of a decaying human corpse from any number of other things that affect soil composition. But it would sure be interesting if this works.

There's this article that I just read this morning. It suggests there are some valid ways to distinguish growth changes in plants caused by dead bodies and those caused by dead animals. Regarding your point, decaying dead bodies in the case of murder will typically be buried, whereas dead animals will die above ground and be scavenged, resulting in far fewer nutrients being absorbed by nearby plants. Of course that would limit its application to murder in comparison to missing people in general.

https://www.economist.com/science-and-technology/2020/09/03/...

Animals that die in burrows would be 'buried', but those animals are probably generally smaller than humans. Perhaps you'd find a few bear skeletons.

As others have pointed out the article mentions this.

I'm a bit skeptical, but I've also read a number of articles talking about how "unnatural" humans biology is due to our diet.

AKA, maybe we have a higher mercury level concentration (artificial sweetener, or whatever) than local species and maybe that can be reflected and sensed in the trees.

My skepticism is more about remote sensing. It wouldn't surprise me if these kinds of things can be detected when a tree's bark/leaves are chemically analyzed. OTOH, being able to sense that optically seems much harder.

They acknowledge it :

> “there would be a need to differentiate effects from human decomposition with those from other animals' decomposition.”

But then :

> However, there could be subtle differences in how plants respond to the decomposition of different kinds of mammals.

I really think it's a long shot and the number of false positive would make the technique impractical, unless you know there's a human body in this forest and you want to exhaust all possibilities to find it.

OTOH, in the circumstances where someone is looking for the body of a fairly-recently-deceased human in a forest they're probably motivated enough to search through quite a large number of false positives to find it. And if the search finds, or can be made to find, only largish mammal corpses then you'd tune out the many dead crows and squirrels and the like. Relatedly, I wonder if the technique might be more effective in the earthwormless parts of North America https://en.wikipedia.org/wiki/Invasive_earthworms_of_North_A... ?

TIL done temperate parts of the world don't have earthworms

The article kind of ends up not giving a conclusive answer to the question posed in the headline though, just a pet peeve of mine. It's really more about the possibility of a new technology helping and even that, as you've said, is a murky option.

The best way to use something like this is probably to find the remains if the murderer confesses and says they're buried "somewhere" in a certain forest. But that's such a niche use case.

False positives are exactly why certain elements of society love this sort of thing.

Maybe a good way to find deer bones or antlers.

CBC story[0] (The Nature of Things “The Salmon Forest” c. 2001) about the work of Dr. Tom Reimchen[1] documenting[2] salmon (unwittingly) supplying a rare nitrogen isotope to hemlock trees.

[0] https://curio.ca/en/video/the-salmon-forest-844/

[1] https://www.uvic.ca/science/biology/people/profiles/reimchen...

[2] http://web.uvic.ca/~reimlab/salmonforest.html

It seems that this would only work once the bodies are pretty thoroughly decomposed, and the trees have had time to absorb the nutrients this creates. I imagine this takes quite a while. A useful technique perhaps, but I can't imagine it solving any hot cases because of that delay.

The problem is that they are underestimating how hard can be the botany. For many people trees are just geometric figures in an architect plan.

1-Is well known that trees have symbiotic fungus. Sometimes the fungus is not present locally, sometimes there are more than one fungus species. Same tree, three types of grow.

2-The same tree can grow different in different soils also

3-The same tree can be perennial or semi-decicuous in dry spells or different years (Totally different color in satellite photos)

4-Some trees (Liriodendron for example) behave very differently just by genetic variation. Each seedling grows at their own pace. Therefore, you can't compare two trees.

5-Some trees are hybrid, their grow can be stunted or increased by hybrid vigor. Is difficult even for trained botanists armed with microscopes to distinguish hybrid oaks or willows (and they hybridize all the time).

6-Is known that sometimes a bigger tree nurtures a smaller tree by mean of a root bridge. Sometimes is the same tree, other a genetically different specimen. So if a sapling suddenly starts to growing faster and greener than the other, maybe it just has connected to rooternet.

7-Or one of its roots managed to enter in a water pipe or reached a very low phreatic level

8-Or is genetically resistant to a common plague that affects 90% of the other trees.

9-Or it has a raptor nest, so it has a lot of nitrogen and zero resident squirrels.

10-Or an alellopathic neighbour has being struck by a lightning and died, stopping to poison the soil.

In brief, they just didn't meditate enough before to jump to this pool. Should have asked a botanist about the project. I'm sad to inform them that the task that they are trying is a titanic effort.

YIL corpse disposal via feeding to pigs is now illegal in many jurisdictions, due to the biosecurity threat: https://news.ycombinator.com/item?id=24397612

What means YIL in this context?

Yesterday I Learned? Or it's just a T(oday)IL typo.

Salmon carcasses are a vital nutrient source for coastal forests[0], so it seems like there might be something to this.

[0]http://depts.washington.edu/pnwcesu/reports/J9W88040015_Fina...

Something like this is a small plot device in the novel The Naturalist by Andrew Mayne.

I heard about a body found in the woods because some unusual plant was growing, germinated from a seed inside their stomach.

Probably apocryphal but hey.

I believe it was a man killed in a cave in Cyprus during conflict there. He had eaten a fig, I believe and the tree grew in the opening of the cave.

I believe it is true and that should help you find a reference.

Here:

https://cyprus-mail.com/2018/09/23/did-a-fig-tree-grow-out-o...

"The remains of the three Turkish Cypriots, the sources said, were found several metres away from the tree roots during the excavations, suggesting it did not grow from a seed inside the deceased man."

There are easier ways to attack the problem.

But it would be low-hanging fruit.

It's kind of a dead-end if you ask me.

Url changed from https://arstechnica.com/science/2020/09/could-a-tree-help-fi..., which points to this.

Reply on news.ycombinator.com