What are you doing in New Zealand, exactly?

I’ve gotten a couple of requests, recently, to describe what it is that I’m researching while in New Zealand. And while I can throw buzz words around like nobody’s business in response, today I realized there’s an even better way to describe my research.

Or rather, a way to let Pete Seeger describe my research for me. Got 4 minutes and 54 seconds? Check out this song for a dulcet-toned description of the whole idea behind what I study (if you’re crunched for time or banjo-averse, start at 4:19 and you’ll get the idea): Green Grass Grows All Around.

Plucky Pete Seeger

This is an old and authorless folk song*, but the same essential pattern has been increasingly noticed in ecological research. In ecology-speak, the “Green Grass Grows All Around” pattern is called “habitat cascade”.

As Pete Seeger croons, “there’s a germ on the wing and the wing on the bug and the bug on the eyelash and the eyelash on the bird and the bird on the egg and the egg in the nest and the nest on the twig and the twig on the branch and the branch on the limb and the limb on the tree and the tree in the hole and the hole in the ground and the green grass grows all around, all around, and the green grass grows all around.”

There are five organisms involved here, by my count: the germ, the bug, the bird, the tree, and the grass. And they’re stacked, sort of like a ladder, each one relying on the one below it for the living space it needs to survive. The germ wouldn’t  be there, let’s say, if the winged bug wasn’t. And the winged bug wouldn’t be there if the bird wasn’t, and the bird wouldn’t be there without the nest-supporting tree. And for the sake of cascade, let’s say the tree wouldn’t have taken root without the presence of the grass. Each organism relies on the rung directly below it to provide space to live- to provide habitat. The cascade comes into it when you look at the relationship between one organism and another that’s not directly below it on the ladder. Without the tree, the germ wouldn’t be there, even if there’s no direct relationship between germ and tree. If you take out one of these foundation species, you get a negative effect that cascades up through the whole ladder.

I made a schematic, which definitely counts as productive procrastination. You can imagine the whole host of indirect interactions at play, though I’ve only included one here.

I study the same thing, really- except in a marine setting, and with a web of interactions rather than a ladder, and with a lot more concern about quantifying those direct and indirect links. If you’re interested in reading the paper that underpins my research, here it is: Habitat cascades: the conceptual context and global relevance of facilitation cascades via habitat formation and modification.

This paper was published by my advisor, Mads Thomsen, in 2010. It’s the first time “habitat cascade” was explicitly named as such. But as the folk song reveals, the actual pattern is as old as dirt– or rather, as old as the germ on the bug on the bird on the tree in the grass in the dirt.

Until next time (when I’ll describe the details of my actual project),

E.

PS:  I remembered this song with a jolt in the middle of a lab meeting today. It was a sweet epiphany, because all of a sudden I remembered my dad singing me to sleep with that song, many and many a year ago. It feels curiously prophetic when I think about it now. (Incidentally, my mother sang me to sleep with “All the Pretty Ponies” but so far I have not developed exquisite horsemanship skills. Will keep you posted.)

*: Hey! There are germs in this song! Germ theory hasn’t been in the general discourse for that long, so how old, really, can this song be? A quick Google search returns one source (thanks, Wikipedia) that says it was written by William Jerome in 1912, but another that lists it in a compilation of Games and Songs of American Children published in 1903. I think it arose from more than just the American folk music tradition, as my advisor tells me there’s a Danish version too. So the origins are murky (as with most folk songs, I reckon) but at any rate it’s been around longer than “marine ecology” has.