Vernal pools are safe havens for creatures such as fairy shrimp, and they have lived through the end of the dinosaurs, the breakup of Pangaea and multiple ice ages. But humans are paving them over.
Christopher Intagliata: This is Scientific American’s Science, Quickly. I’m Christopher Intagliata.
When I first started working on this series about vernal pools and became convinced I had to go see them for myself, one of the most surprising things was where people kept telling me to go to see them.
Chuck Black: This landmark is by far the largest and most pristine concentration of vernal pools left in San Diego County and possibly in California.
Intagliata: A preserve of hundreds of acres of wild land, containing more than 1,000 vernal pools—it’s also part of a Marine base outside San Diego: Marine Corps Air Station Miramar. And my tour guide was a wildlife biologist employed by the Department of Defense, a guy named Chuck Black.
Intagliata (tape): I never thought that ... for this story I would be coming to a military base to find the ... natural resource.
Black: Yeah. Yeah. Well, lots of people don’t associate military bases with ... conservation efforts, but….
Intagliata: It’s true—when I think conservation, I think of roadless stretches of the Sierra Nevada or remote patches of the Mojave Desert.
Here the natural wonder is sandwiched between a highway, a landfill and a runway. And there’s a reason this military base is the largest remaining stronghold of vernal pools along the southern California coast. Lots of other stuff around here got developed.
Black: Flat mesa tops like this were the prime areas for development during the 18th, 19th and 20th centuries.
Intagliata: The vernal pools became farmland, houses, shopping centers.
Black: It’s estimated that over 98 or 99 percent of the vernal pools that formerly existed in San Diego are now not here any longer because of the development.
Intagliata: And if you look statewide, the numbers aren’t all that different, and vernal pools are thought to be among the most threatened ecosystems in the state.
Sean O’Brien: A lot of people know that 90 percent of vernal pools have been lost from the Central Valley since European colonization. But what people don’t know a lot about is that these losses are ongoing. This isn’t just a historic problem.
Intagliata: This is Sean O’Brien. He’s a senior wildlife biologist with ICF, that’s a consulting firm. And he does biological surveys of vernal pools before developments and tries to recommend ways to avoid harming vernal pools—and if that can’t be avoided he advises ways to make up for the loss elsewhere.
And he says there are a number of factors today that threaten vernal pools and the things that live there, but one stands out among the rest.
O’Brien: I think it’s safe to say that habitat loss is the number one concern by a landslide.
Intagliata: A recent study by vernal pool consultant Carol Witham showed that between 2005 and 2018, 9 percent of the Central Valley’s remaining vernal pool habitat, 76,000 acres worth, was wiped out.
And more than 90 percent of those losses were unmitigated. What that means is that the pools were destroyed without adhering to regulations, which require documenting the loss or preserving pools or restoring them elsewhere to compensate.
Witham's report says the majority of the pools are being destroyed to make way for vineyards and orchards.
Witham: And there are some consultants making a lot of money helping people do that.
Intagliata: Witham explains that a lot of the habitat losses documented in her report is accomplished with a sort of tricky workaround.
Witham: It looks like in a lot of cases they avoided at least the larger vernal pools and only planted around them, not through them. But for all intents and purposes, that endangered species habitat, if it isn't already gone, it will be gone in very short order.
Intagliata: Vernal pools tend to be at the low spots–it’s right where the water pools. It’s also where contaminated water from agriculture flows, which can kill things living in the pools. And if the pools were eliminated "by mistake" like this... well, she says that's a lot harder to enforce.
Witham: This is part of the reluctance of the regulatory agencies to do enforcement actions. Because they can't prove that the activity killed endangered species because they didn't actually go in and screw up the vernal pools intentionally at the time they put in the trees. But over a very short period of time, all of their activity around the vernal pools will destroy the vernal pools.
O’Brien: You gotta feel for these ranchers, too, who … see their neighbor just put in an orchard and became millionaires while they have done the right thing and haven’t converted their vernal pool complex into an orchard, and they are, they’re not getting money out of that. They have no incentive to preserve their land.
Intagliata: Private ranchers are by far the biggest landholders of the Central Valley’s remaining vernal pools. And to be fair–some ranchers are actively preserving the pools on their land, through various types of conservation agreements.
But even when they aren’t, and vernal pools are being transformed into orchards, O’Brien says the fairy shrimp seem to follow the famous Jeff Goldblum line from Jurassic Park ...
[CLIP: Jeff Goldblum in Jurassic Park: “I’m simply saying that life, uh, finds a way.”]
O’Brien: You’ll still see shrimp hatch out in these plowed fields. They certainly are resilient creatures.
Shannon Blair: Yeah, from a—zoomed out on a very, very long view, I think fairy shrimp as a group are gonna be okay.
Intagliata: I talked to Shannon Blair about this. She’s a molecular ecologist at the University of Idaho who did a lot of work on fairy shrimp as a grad student and postdoc at the University of California, Davis.
Blair: I think the dangers of losing vernal pools is that they aren’t just isolated habitats. They’re deeply connected to the agricultural productivity of the region, to the wildlife and the migratory birds of the area, and they protect and support native amphibians. So you lose a lot more than just a pond when you lose a pond.
Intagliata: But just looking at the fairy shrimp, she says they’re survivors—despite what humans might be able to throw at them.
Blair: They’ve lived through the breakup of Pangaea. They’ve lived through the K-T extinction. They’ve lived through the meteor that killed the dinosaurs. They’ve lived through ... multiple ice ages, and they are still—as an order, they’re found all over the globe: in the desert, in the Arctic..., on rocky outcroppings. They’re found in the rich jungles of South America. They’re found on islands.
They represent an ability to survive in very difficult, very changeable conditions. And they do that by sort of waiting until things are perfect before they emerge again and changing rapidly and adapting rapidly to new environments as they arise.
Intagliata: Her point reminded me of something Chuck Black had told me while we were wandering the vernal pools at Miramar.
Black: I’ve even seen fairy shrimp in the asphalt tie down hollows on the runway that are only about as big as your cupped hands.
Intagliata: They can survive in little puddles on the runway. These things truly are hardcore.
And I should stress that no one told me we shouldn’t be concerned, alarmed even, at the vernal pools vanishing right now, today.
But there might be reason to hope.
Black: Luckily, they’re very tough species. They withstand the disturbance and stuff. And so if you dig a hole that holds water long enough, most of the plants and fairy shrimp will do just fine. If you pave it over with a parking lot, no way. So... [laughs]
Intagliata: If we don’t completely destroy the remaining vernal pools, it seems the extraordinary creatures that call them home might just find a way to hang on.
For Science, Quickly—I’m Christopher Intagliata.
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