I had a hugely lucky moment this morning while I was riding my bike down by the river.

The bike trail parallels one of the riverside drains, small canals that flank the Rio Grande through the Albuquerque reach. Out of the corner of my eye, I spotted an enormous bird, lunging at something in the water. By the time my gaze settled, the big black-crowned night-heron had a fish in its mouth.

The night-herons live around here, but they’re relatively reclusive, so I felt lucky not only to see one, but to see one in action. We’ve also had an osprey around this spring, which along with the great blue herons that live up and down this stretch of river and the bald eagles that winter here are top-of-the-food-chain critters.

My favorite blue heron story is a very early morning bike ride on a very cold morning. It was just after sunup, and my friend and I had stopped on the Alameda Bridge, a pedestrian-bike bridge over the Rio Grande up at the north end of town. It was winter, the river was low, and there was a great blue sitting in the middle, in shallow water, absolutely still. All of a sudden, its neck snapped down, and it came up with a fish.

Rio Grande silvery minnow, Aimee Roberson/FWS

That’s a bit of a ramble, sorry, to get to the Endangered Species Act. Here in the Middle Rio Grande, the Rio Grande silvery minnow is the endangered little fish that sits at the fulcrum of the politics of water, development and ecosystems. We’ve sufficiently modified our river that it bears little resemblance to the ecosystem that once flourished on the broad valley floor of what is now central New Mexico.

People here who complain about the ESA like to complain about “that damn little fish”, but it’s worth noting the actual language of the Act:

The purposes of this Act are to provide a means whereby the ecosystems upon which endangered species and threatened species depend may be conserved…. (emphasis added)

Which means that one of the points of ESA protection is so that my night-heron, and the osprey and bald eagles, have something to eat.

I originally wrote above that we had “screwed up our river”, rather than merely “modified” it, but that’s a value judgment. Many people prefer it this way. In fact, given that much of our societal infrastructure in the greater Albuquerque area, from the old farms in the valley to the way we’ve built our city, depends on the engineered river we have now, it seems fair to argue that people prefer it this way, which was one of the points I made in a piece earlier in the week. There’s no a priori right way to run a river, but rather a series of tradeoffs:

Different people value water and the natural world in different ways. We use our political system to sort out the resulting disagreements. This is how we ended up with the Rio Grande we have — heavily engineered, designed first and foremost to move water for human use and prevent flooding. That is largely what the people who live here, acting through their political institutions, seem to have wanted.

All this is an extremely round-about path to a terrific New York Times riff by Felicity Barringer on tradeoffs and the ESA. It’s about California and its damn fishes, but her points apply equally here. She’s writing about federal judge Oliver Wanger, who has been tasked to sort out the competing interests of not only fish v. humans, but also the interests of humans who depend on fish:

In a courtroom hearing in late March, he said, “The economic pain and hardship has been no less to the fishing industry that relies on salmon than has been the economic consequence to the Central Valley agricultural community.”

He has also referred to the Supreme Court’s landmark ruling in Tennessee Valley Authority v. Hill, which declared that the primary purpose of the Endangered Species Act was “to halt and reverse the trend toward species extinction, whatever the cost.”

Judge Wanger reframed the decision, writing, “This case involves both harm to threatened species and to humans and their environment. Congress does not nor does T.V.A. v. Hill elevate species protection over the health and safety of humans.”

It’s worth noting that the canal in which my night-heron was dining is not natural river. It’s human plumbing, designed to drain shallow groundwater and carry agricultural runoff. And for the record, while the night-heron flew off quickly, it was pretty clear from its size that the fish in its mouth was not a silvery minnow.