Last night I went to see a noisy staging of snow geese. It was a pretty marvelous sight. And you think to yourself—you’re maybe a little impressed at the showing of birdpower and a little amused by the showing of people parked alongside the road to watch the avifauna—but you have to ask yourself, what does 45,000 snow geese even mean? 45,000 is the number, based on previous years’ records, that I’m assuming I saw. I wouldn’t be surprised if it were true. A writhing sea of white and you more or less lose track of numbers. It could have been more geese; I wouldn’t know.
It’s definitely an impressive spectacle. And unlike witnessing noisy flocks of birds you know to be alien—starlings, for instance—you think: this is a good thing. You want it to be a good thing, that all these birds are existing, thriving. You want sheer numbers to be an obvious demonstration of the species’ robust health.
But of course, it’s not as clear-cut as all that.
Witness the spectacle of the greater snow goose’s more populous cousin, the lesser snow goose:
Large numbers of these lesser snow geese grubbing around streams makes the soil unstable, makes the stream-bank widen through erosion, exacerbated (as you might expect) by spring flooding (in their northern habitat). Lesser S.G. sticking their bills around in the soil leads to increased evaporation of water from the soil, which in turn makes the soil more alkaline and increases salinity. Which kills willows (above picture). Etc. etc.
The point not necessarily being that 6 million lesser snow geese is an irrefutably bad thing, a blanket statement like that being essentially ridiculous, but that it pays to heed the specter of ‘carrying capacity’. Geese taxing their (relatively) limited resources—particular habitats in which they thrive, particular foods they need to remain healthy, particular climactic conditions on which they depend—shows a clear example of what’s happening, but in a less obvious way, to humans. “How Many” is a question that gets bandied about till those doing the bandying are blue in the face. A better question being, How Much?
The answer to the question “How much can a snow goose reasonably be expected to consume?” is fairly straightforward, depending on the total population, the density of that population, and ecosystem factors (e.g., richness of the biota).
The answer to the question “How much can a snow goose reasonably expect to consume” is similarly straightforward, but has a markedly different answer. Assuming that a snow goose can have any kind of expectation, we might imagine that each snow goose expected to consume as much as possible, more nourishment correlating (up to a certain point) to a greater chance of survival. Sure, a hideously obese snow goose isn’t going to have very bright prospects for survival, but then again, other factors are probably going to prevent that from happening. Population density (other geese trying to get food in the same area) and physical activity in all likelihood militate against such a goose from existing, would be my guess.
There is no earthly reason for us to pretend that “How much can a human reasonably expected to consume” and “How much can a human reasonably expect to consume” should (or even can) have identical answers.
But in the interests of survival, we’d better hope that the gap between the two expectations narrows, because as a matter of physics and biology the former answer will triumph. You can’t cheat carrying capacity.
Snow Goose References:
Lesser Snow Geese and the Trophic Cascade
Over Abundant [sic] Snow Goose Population – Environment Canada
Snow Geese Taking a Gander at Pennsylvania