Seedy Neighborhood

There are several American Elm trees on my block in Park Slope, Brooklyn, and just as they do every spring, they are squandering their resources in profligate and futile excess.

Ecologists have noticed that living things tend to use one of two reproductive strategies. In the first, the organism creates an enormous number of potential offspring, each of which requires only a small investment of resources to create, and none after that. When the ecosystem is already at or near its “carrying capacity” (K) for that type of organism, the odds are that few or none of the potential offspring will survive. However, in situations where the population of the species in question is well below K – meaning that there are lots of “job openings” available – the growth rate (r) of the population will increase exponentially until K is approached.

Organisms that use this approach are called “r-strategists”. Typically they do well in transitional habitats, such as freshly burned or plowed fields, where they can get a quick foothold before being driven out by competitors. They rely on good dispersal and sheer numbers for their success. Oysters, for example, might release hundreds of thousands of eggs in a single season; if only a few get by, the effort was worth it.

The other approach, which works better for stable populations that are near their habitat’s carrying capacity, is called the “K-strategy”. That’s what we humans do – we have very few offspring, at a high cost (with two kids in college, a very high cost, let me tell you), but we do our damnedest to make sure they survive.

Well, elm trees are r-strategists par excellence, and this year the ones on my block have outdone themselves. Elms produce a waferlike seed called a “samara”, a flat papery disc weighing slightly more than an electron. This year we are snowed under by an incalculable multitude of elm samaras, piled in huge drifts at the curb, on the stoops, against the cars, on the windowsills, in our mailboxes, everywhere. When it rains, which it is starting to do as I write, they turn to a dense porridge-like sludge. The aggregate elm-samara volume on my block alone would probably fill a good-sized dumpster.

And of course it is all in vain. There isn’t a transitional habitat, a plowed field or recently burned forest, anywhere in sight, unless you count the recent gentrification (with attendant construction of high-rise condos) over on Fourth Avenue. But that isn’t the sort of transition the elms are interested in.

They don’t seem to be letting it get them down, though. There’s always next year.

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