Podcast #26: The Fate of the Delta Smelt

Our latest Undark podcast looks at the big debate over a tiny imperiled fish, a science magazine’s racist past, and gourmet bugs.

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Join our podcast host and former NYT editor David Corcoran as he talks with Sharon Levy about a tiny imperiled fish that’s stirring a big controversy. Also, Seth Mnookin on National Geographic’s race issue, and Jason Plautz on gourmet insects.


Here’s a full transcript of the podcast, lightly edited for clarity.

David Corcoran: This is Undark. We’re a magazine devoted to exploring the intersection of science and society. And we’re this podcast.

Hello again. Welcome to Episode 26. I’m David Corcoran.

For our cover story, a tiny fish and a gigantic environmental problem. Science writer Sharon Levy joins us to talk about it. Sharon, welcome to the podcast.

Sharon Levy: Thanks, I’m happy to be here.

David Corcoran: OK, so what’s the fish and where does it swim?

Sharon Levy: This is the Delta smelt. It’s a translucent little creature about three inches long. It was once very abundant in the Sacramento-San Joaquin Delta in central California. And it thrives in cool, turbid water, where it feeds on tiny zooplankton. But its population has crashed and it’s on the edge of extinction now.

David Corcoran: And why has it become such a focus of attention?

Sharon Levy: The fishery ecologist Peter Moyle originally started studying the Delta smelt in the 70s because it was very abundant. It was easy to find lots of samples. But ironically, after he had invested a lot of time studying the fish and working at its life history, he tracked a major crash in the smelt population in the 1980s.

And by 1993, the fish was listed as threatened under the federal and California Endangered Species Acts, and since then, in 2009, California upgraded the listing to endangered.

The delta is the hub of California’s water supply system. And increasing amounts of delta water have been diverted to cities and farms over the years. And the decrease in water in the delta is a large part of what’s affected the smelt and other native fish.

The biological opinion, issued by U.S. Fish and Wildlife Service after the smelt was listed, limits the pumping of delta water where there are conditions that threaten the fish. So this little fish that people rarely see unless they’re researchers has ended up in the middle of a big clash between conservation and the water-hungry farms and cities to the south of the delta. Especially farms in the San Joaquin Valley.

David Corcoran: OK. Before we get to the why and how this species became so imperiled, let me ask you how you got interested in this story.

Sharon Levy: Well, I happened to meet Peter Moyle, who is the eminent fish ecologist in California. And if you’re at all a biologist, which I am, you’ve seen some of his books, like “Inland Fishes of California,” which is the reference on California fish. I happened to meet him at a conference, and he was talking about the Delta smelt as a native species that’s on the endangered species list and is struggling to survive in an ecosystem that’s been completely transformed by humans. The delta’s flows have been diverted. It used to be full of meandering channels that went through marshes; those have all been leveed, walled off from the influence of the tides. And the whole system is now dominated by an array of invasive species.

After hearing Peter talk about this, I was intrigued by the problem of trying to manage a listed species when its original habitat has pretty much vanished.

David Corcoran: Specifically, how did the smelt become so endangered?

Sharon Levy: That’s not a simple question to answer. Moyle and other researchers have studied this a lot over the past 15-20 years or so. And there’s no one answer. There’s an array of changes in the delta that have ended up making it a pretty hostile place for the smelt and other fish species that evolved there.

First of all, there’s a lot less water than there used to be because we’re diverting so much of the water for our own uses. Second of all, it used to be a wetland where there was lots of variety of different kinds of water depths and different places to hide among the reeds. And we’ve simplified it all, we’ve channeled all the water in straight channels and walled off the influence of the tides from San Francisco Bay.

And one of the major blows is over the past century or so, we’ve introduced a whole mish-mosh of invasive species, and they totally dominate the delta at this point.

David Corcoran: What are some of the species?

Sharon Levy: Well, let’s see, some dramatic examples would include a little clam. It’s about the size of your thumbnail. It’s called the overbite clam. It’s originally from Asia, and it was accidentally released, probably from ballast water, in a ship that came to San Francisco Bay.

It was first detected in the estuary in 1986, so not that long ago. But in that time it has been fruitful and multiplied, and it now constitutes huge mats that cover most of the estuary bottom in parts of the western delta and eastern San Francisco Bay. And these clams are filter feeders and they’re very efficient, so they just filter the water through themselves and eat all the zooplankton and phytoplankton in the water. And as a result of this clam, the food that used to feed young Delta smelt and other open-water fish has more or less disappeared.

So there’s a place at the western edge of the delta called Suisun Bay that used to be a major nursery for the smelt. And there is very little food for smelt there anymore because of the overbite clam population.

David Corcoran: You also mentioned some sport fish that we’ve all heard of that are really not native to the delta but are kind of important there now.

Sharon Levy: Yeah, one prime example would be the striped bass, which is originally a native of the East Coast of North America. It was introduced to San Francisco Bay on purpose in the late 1800s because it was a game fish people like. And it’s done pretty well in the bay and the delta. People really like to fish for it.

The population has been going down for the same reasons that Peter Moyle considers the striped bass an honorary native in the delta. He says that the striped bass is really one of the best existing indicators of habitat conditions because native fish, like the salmon and the smelt, are becoming so rare you can’t really track them very well.

But the striped bass share some habitat needs with those natives. It needs cool water; in its juvenile stage it needs a lot of zooplankton to feed on. And so where there’s a pretty good population of striped bass, some of those native conditions are hanging on in this modern milieu that’s so different.

David Corcoran: OK. Let’s talk about this all-important word “endangered.” I understand the Delta smelt is threatened under the federal Endangered Species Act and endangered under the California Endangered Species Act. But what does that mean in terms of public policy? What has to be done to protect the fish and try to bring it back?

Sharon Levy: The problem of the single species focus of the Endangered Species Act is when the law was enacted in 1973, very few people in Congress voted against it. And the focus was on charismatic large animals like grizzly bears and bald eagles and wolves. And at the time, people just weren’t thinking about some of the conservation concepts that are really important today.

Among those concepts is the simple understanding that you can’t protect, say, a Northern spotted owl unless you protect its habitat. The species won’t make it without its habitat. So that’s a pretty simple issue that has been addressed as early as the 90s by trying to use habitat conservation plans under the Endangered Species Act instead of just a single-species recovery plan.

But Peter Moyle and other ecologists are now bringing up a different concept that’s really important, and that’s the concept of trying to do conservation in what they call a novel ecosystem. And the delta is an example of a novel ecosystem.

It’s full of species from all over the world that have never coexisted in this arrangement before. It’s been totally arranged by humans. And in that scenario, the ways that you can go about managing native species are gonna have to be pretty different from what’s happened in the past.

David Corcoran: The smelt is not a particularly popular fish to many people in California. It has become the focus of some pretty vehement criticism. Can you talk about that a little?

Sharon Levy: Sure. One way that the smelt is an example of some of the downsides of doing conservation one species at a time — that the Delta smelt has become a scapegoat. So here it is, it’s a little fish that back in the days before we rearranged the delta, it was very abundant, but its strategy in life was to be invisible. It survives by being invisible to predators.

Well, now here’s this fish that specializes in invisibility and it’s in the middle of a huge public controversy because it is the first fish that was listed as endangered in the delta and because it’s easy to dislike it. No one ever sees it. No one fishes for it. It doesn’t really have a lobby.

It’s pretty common for people, say, in Fresno or the San Joaquin Delta to rage about water being used to protect the smelt and creating limitations on how much delta water can be pumped to their part of the state. And it’s easy to make fun of that and say, “Oh, great, you’re depriving all these farms and all these families of water in order for this little fish to survive.”

But the truth is, even if you’re willing to sacrifice the smelt, if you don’t watch the flows of water we’re gonna lose all the native fish in the delta. And then even if you’re willing to say, “OK, we’re gonna let every trace of the native ecosystem die out,” the truth of the matter is the freshwater delta that we’re accustomed to today only exists because we have engineered all the flows in and all the flows out. If we don’t manage those flows very carefully, we will get saltwater intruding in the delta which was historically the normal state of affairs.

Historically, saltwater from the bay flowed as far inland as the present-day city of Sacramento. So if that happened today, there would be a serious crisis with California’s water supply. You can’t use saltwater to drink or to water farm fields.


[Editor’s note: While seasonal intrusions of saltwater historically reached the western reaches of the Delta adjacent to San Francisco Bay, the assertion that saltwater intrusions in the historic Delta reached as far as Sacramento is incorrect. It is true, however, that the modern Delta is heavily and necessarily managed to maintain low salinity today.]


David Corcoran: So this problem turns out to be hugely more complicated than just this one species. But the Endangered Species Acts were really designed to do exactly what your scientist source, Peter Moyle, says should not happen: rescue one species at a time. Is it possible to rewrite the Endangered Species Act? And if so, what would take its place?

Sharon Levy: That’s a really profound question. If you look at the ecological literature, there are scientists who have been critiquing the Endangered Species Act for many years —probably since shortly after the act became law.

But the problem with it is, even though the law definitely has some glitches, it’s a bedrock of conservation law and it’s been used to protect both single species and their habitats all over the country. So we don’t want to lose it.

And conservationists have what appears to be a very justified fear that if they push to amend the law, it’s going to end up being gutted and not having any teeth at all. So politically it’s very difficult to change the Endangered Species Act.

But there are efforts to try to change the way we approach these problems, and one example is in California, there is a large habitat restoration program in the delta that’s called California EcoRestore. And their goal is to restore tens of thousands of acres of wetland and marsh habitats for Delta smelt and other native fish — but also for the whole array of native species that use those kinds of habitats.

But the leverage to get funding and to get space to do this restoration is based on the biological opinions that were written for Delta smelt and winter-run Chinook salmon. So there’s ways in which people are using the leverage of the Endangered Species Act to do some broader restoration project.

David Corcoran: And I guess you’ve got an administration in Washington, when we talk about funding, that is not terribly friendly to the idea of ecological restoration.

Sharon Levy: Yes. That’s an understatement. The Trump administration, as just about everyone knows, is set on rolling back all kinds of environmental protections. And that includes protections for endangered species and for clean water.

And it’s very worrisome, because an administration that doesn’t want to protect the environment can do a lot of damage by simply turning a blind eye and not enforcing the rules. This administration’s going beyond that and attempting to undo the rules. The only comfort is that while they tend to make proclamations that show up in the press as “Well, we’re just taking this regulation back, we’re undoing it,” the truth in most cases is that they can’t just do that by fiat. There’s a legal process involved that can take quite a while. And in many cases when they try to do that, it will be contested in court.

My personal hope is all that will be delayed. In the case of the Delta smelt, there’s an interesting little anecdote. Trump had campaigned in Fresno in 2016 when he was a candidate. And he made a campaign stop, mocking this smelt conservation and promising to guarantee more flows of delta water to the San Joaquin Valley. And that was very popular at this campaign stop.

Recently the federal Bureau of Reclamation, which runs the Central Valley Project, one of the major exporters of delta water, announced that it intends to maximize water delivery south of the delta. So that’s the administration’s first effort to make good on Trump’s campaign promise in 2016 in Fresno. But it’s expected to trigger an intense battle with California regulators, many of whom consider it a point of pride to resist. So I can’t predict how that’ll turn out.

David Corcoran: Let me ask you one other question. You spent a lot of time with Peter Moyle, the fisheries ecologist who’s probably, sounds like, the leading expert on the Delta smelt. How does he feel about all this?

Sharon Levy: Well, Peter Moyle’s a very interesting guy. I was fortunate to be able to go out on a survey boat with him on Suisun Marsh in the western delta, an area he and his colleagues have been studying for more than 20 years. And in that whole day of traveling on the boat with them while they made multiple stops and trolled fish and invertebrates out of the marsh, we saw lots of creatures, but only two native fish. That is all. Two native species in a whole day.

So although I had read Moyle and other people who had written papers about how invasive species dominate the delta, it makes it real when you go out on a boat and see that. And the great majority of creatures in the delta today have been brought there from all over the world. And they’re now coexisting and competing and preying on each other like animals do in ecosystems.

That really brought the notion of a novel ecosystem to life for me. I think Moyle loves the Delta smelt and the other native fish. But after a lifetime spent tracking them and watching them decline, he believes we have to manage the delta that we have now. It’s not going to be possible to get back to pristine conditions.

There are probably ways to save salmon and maybe even smelt, although he seems pretty pessimistic about the smelt. But rescuing the native fish is going to take some invention and involve [creating] some niches for them in what is essentially a man-made ecosystem.

On the other hand, it’s really important that we manage this system well and not just dismiss it because it’s a mish-mash of invasive species. Because if we don’t manage it in a thoughtful way, then a very few weedy species like the aquatic plant Brazilian water weed, which is taking over large sections of the delta, will completely take over. And the delta’s gonna lose the biodiversity that it still has.

David Corcoran: Sharon Levy is a science writer based in Northern California covering the environment and natural resource issues. Her new book, “The Marsh Builders: The Fight for Clean Water, Wetlands, and Wildlife,” will be published by Oxford University Press in May. She joined us from the studios of public radio station KHSU, in Arcata, California. And listeners, you can find Sharon’s article about the Delta smelt in our magazine at Undark.org.

Sharon, great story. Many thanks.

Sharon Levy: Thank you.

David Corcoran: Joining us now is Seth Mnookin, our commentator on science in the media. Hello, Seth.

Seth Mnookin: Hello, David.

David Corcoran: This week I want to talk about a favorite magazine, National Geographic, which has just published something called the Race Issue, with a lead editorial whose headline reads, “For decades our coverage was racist. To rise above our past we must acknowledge it.” What is this all about?

Seth Mnookin: Well, I think a lot of people would say, an overdue reckoning on the part of National Geographic with the tenor of its coverage of people from other parts in the world, from the United States and in fact also its lack of coverage of people in the United States.

If you look back over issues of National Geographic, stretching back decades, people, especially people of darker skin color from elsewhere in the world, were often portrayed as some sort of savage people. Sometimes captioned or described as being of lower intelligence.

There was a whole sub-genre of photographs that ran within National Geographic of native people from around the world being fascinated by the technology white Westerners brought them. You know, cameras and recording equipment.

And when you look back at it, it’s the kind of coverage that can make you pretty queasy. It’s pretty revolting. And some people would say this is overdue, but finally in 2018, the magazine really took a concerted look back at its past and tried to reckon with what that history was.

David Corcoran: The main piece in the magazine, apart from this editorial, was a reported essay by the Pulitzer Prize-winning writer Elizabeth Kolbert on racism not as a biological phenomenon at all, but kind of a social construct.

Seth Mnookin: Yeah, and that’s a topic, I think, that’s very present in the news today. It’s a subject about which there remains a fair amount of debate. Although I think increasingly that is the view that if you look at the evidence, it’s hard to argue with that. With race as a social construct instead of a biological one.

And I think even that article, in and of itself, even apart from the rest of the issue, is a really fascinating and important article. And I think the type of thing that National Geographic has signaled that it wants to do and it hopes to do moving forward, is distinct from what it has done in the past.

In that lead editorial, the editor of the magazine notes that she is not only the first woman editing the magazine — a woman named Susan Goldberg — but also the first Jewish person editing the magazine. Both categories that had been discriminated against in the past.

I completely take her at her word that this does signify a change in the approach of the magazine. Not so much a change in the approach, because I think [that] in the past several decades National Geographic’s coverage wasn’t anything like what it had been. But it signifies a more conscious embracing of tackling these difficult issues.

David Corcoran: Yeah, I think it’s a signal to other publications and to science in general to take a look back at our past and confront these things head on.

Seth Mnookin: Yeah, it would have been great to have seen this two years ago before it sort of became impossible to ignore and to avoid these types of discussions. I mean, this is a conversation that is literally taking place not only in publications, but in every sphere of American life.

At MIT, we just undertook a big study into the role of slavery, people who were integral in founding the institute. It’s happening at educational institutions across the country. So as welcome as this is, it does not really feel like National Geographic is stepping out in front and leading the conversation, but is taking part in a conversation that had really already begun.

That’s not to say that it’s not welcome, but I don’t want to overstate their role in bringing this conversation to the forefront.

David Corcoran: There was one other very interesting critique of this race issue of National Geographic by Undark’s media columnist, Michael Schulson. You want to tell us about that?

Seth Mnookin: Yeah. It really was fascinating. Along with this issue, both within the issue and online, there’s pretty aggressive marketing of a $100 genetic testing kit that National Geographic is selling. They’re very big players in the genetic testing marketplace. For $100, you can buy one of the society’s Gene 2.0 kits. And Gene 2.0 is an entire project that National Geographic is undertaking, part of its Genographic project, which is a research program that, among other things, aims to trace ancient human migration by mapping DNA of people from all around the world — and especially members of indigenous groups.

And there have been some criticisms of this: Essentially, here again is a powerful and extremely wealthy Western institution asking for biological samples from indigenous people from around the world. And in fact, not only asking for these, but monetizing that effort.

There were people, and Michael among them, who raised the question as to whether this was a little bit crass. And certainly I think at the very least made the entire effort seem possibly slightly less noble than it might have been. On the flip side, National Geographic throughout its history has always had a merchandising arm that has sought both to further its scientific explorations and also raise money for those scientific explorations. You could say that it’s very much in character with what the society has been doing more or less throughout its history.

David Corcoran: I’m of two minds about this too. It does seem a little commercial to be selling these ancestry kits. On the other hand, they’ve been collecting this data for quite a long time, and the aggregate picture when it finally comes out should be really interesting.

Seth Mnookin: Yeah, they launched the Genographic project, I think, in 2005. It’s been 13 years. It’s gonna be a huge collection of DNA. What left me with a little bit of a bad taste in my mouth is that [it was] simultaneous to their saying we really need to take a sober and clear-eyed view at our past. I think you could level the argument against them that they are not taking a very sober and clear-eyed view of their present. And that they didn’t, in this issue, raise any of the concerns that have been brought up about this effort. And I think that would’ve been a really affective way to address this. Include information about Gene 2.0 and at the same time, say this is some of the objection that have been raised about this and this is why we feel that those do or don’t have validity. Or however they wanted to approach that.

At the same time, I do feel that National Geographic as a publication on the whole is something that I very obviously would rather see out there. And in order for it to remain out there, it needs to bring in revenue. It’s much more expensive to produce the magazine than they get through revenue through the magazine.

And I’m sort of reminded of critiques of mainstream organizations like The New York Times, the criticism that they got when they launched a Style section — that this was somehow beneath The Times. And which sort of misses the point that the fact that The Times does sections like the Style section and brings in advertising is why they’re able to then also have foreign correspondents.

But I do think it would have behooved the society to have at the very least acknowledged that there have been criticisms of the Genographic project and of these Gene 2.0 direct-to-consumer testing kits.

David Corcoran: Well, Seth, I’m afraid it’s time to say so long. Listeners, we are about to go to a different format for the podcast, which will include some new features. So, Seth, I want to thank you for more than a year of astute and good-humored contributions to the Undark Podcast. It’s been great working with you, and please don’t be a stranger.

Seth Mnookin: Yeah, thank you. It’s been great doing this. And of course, can’t wait to hear all the new things that are gonna be in the podcast future.

David Corcoran: So long, Seth.

Seth Mnookin: Thanks, David.

David Corcoran: Have you thought about how your dinner affects the climate? As more research emerges about the environmental impact of meat, some companies are turning to bugs as a new food source. That’s right: crickets, mealworms, grasshoppers, and even spiders could become staples on your plate. Reporter Jason Plautz takes us to a farm in Denver trying to take bugs from lizard food to the mainstream.

Jason Plautz: I’m in a shipping container tucked in a parking lot behind the bodega off a busy street in Denver’s Westwood neighborhood. And Wendy Lu McGill is showing off her livestock.

Wendy Lu McGill: So I don’t know if you can hear in the background the crickets chirping. That means that we have a lot of adults. And chirping is a sign that they’ve reached sexual maturity and that they’re going to be reproducing.

Jason Plautz: McGill is the founder and CEO of Rocky Mountain Micro Ranch, one of the few farms in the U.S. raising insects for human consumption. Her crickets, mealworms, waxworms, and tobacco hornworms are most popular as a roasted snack food. But they’re also on the menus of five local restaurants.

So, why bugs? Agriculture contributes 15 percent of the world’s greenhouse gas emissions, and half of that is for livestock. Think of the resources it takes to raise cattle or chicken, then compare that to McGill, serving up droplets of water to her insects in the shipping container.

According to a study by the United Nations Food and Agriculture Organization, raising a kilogram of cricket protein requires less than 8 percent of the land it takes to get the same amount of beef protein. The water savings are even bigger. You’d need 22,000 liters of water to get as much protein from beef as you could get from crickets with just a single liter.

The push to find a more sustainable food source is a major driver for companies to bring bugs to the mainstream. Dried crickets are being packed into protein bars, pasta, and brownies, and restaurants are dishing up grasshopper tacos and cricket pizzas.

Robert Nathan Allen: The broader food conversation is already looking at where does our food come from? How does it get to our plate? What happens to it afterwards? How are the animals treated? All these questions fit in perfectly with insect agriculture.

Jason Plautz: That’s Robert Nathan Allen, founder of the Austin-based nonprofit Little Herds, which is promoting edible insects. He said growth is hard to measure in an industry with so few companies that anecdotal evidence suggest it’s trending up.

Pepsi CEO Indra Nooyi called them the snack of the future. And Mark Cuban invested in a cricket company on “Shark Tank.”

“Shark Tank” voiceover: You’re obviously jumping at the opportunity here to get on board with the growing global business. So who wants to join Chapul [Cricket Flour] and help us to feed the revolution?

Jason Plautz: There’s also the potential to use insects as a feed for other livestock. Replacing the big carbon footprint of corn-based feed with a more protein-rich option. But for the industry to take off, insect farmers are gonna have to make a product that people want. That means figuring out how to make fatter bugs, even feeding them on flavors like honeycomb or basil to change their taste.

Back at the ranch, McGill’s bugs are kept in plastic containers like you’d get at Home Depot, and scurry around on egg crates which have pockets that crickets can hide in. They’re kept moist with spray bottles and damp paper towels because a water dish might drown them.

The most high-tech part of the ranch is the nursery. A small tent that uses a wireless temperature control to keep things nice and humid, the way cricket babies prefer.

Unlike big farms, raising crickets for the larger pet food industry, McGill sells to a smaller market. And crickets only live about six to eight weeks, a short lifespan that means McGill has lots of opportunity to experiment with growing conditions and diet.

Wendy Lu McGill: Most commercial farms are feeding something that’s akin to a cricket chow or an insect chow. And it’s not a feed that I would choose to use for people to eat.

We are using spent brewing grains from breweries, microbreweries primarily, to feed our micro livestock.

Jason Plautz: The brewing grains aren’t just a Colorado thing. McGill says the combination of barley and wheat is closer to what crickets would naturally eat.

Wendy Lu McGill: The difference with cricket chow is that it’s supplemented with fish meal — it’s not very close to their natural diet. They would not be eating fish in the wild. It also makes them fishy because their bodies are so small that flavors that are in their feed can come through.

Jason Plautz: OK, it’s a cool farming experiment. But do they taste good? I went to Comida Cantina in Denver’s RiNo district to find out. Head Chef Jacqueline Perez put cricket tacos supplied by Rocky Mountain Micro Ranch on the menu a year ago and continues to sell out. She says Wendy’s new feed has really paid off.

Jacqueline Perez: They do taste better. They’re a lot plumper too, so I think that’s nice. And it’s not that they’ve been packed with anything they shouldn’t be eating. They’re all eating the proper feed. Cause before if they’re so small and then you roast them, they don’t really carry that much of a flavor. These are able to stand up more.

Jason Plautz: She brought out some of the tacos, which are packed full of roasted crickets along with some avocado, pico de gallo, cheese, and a chili rojo salsa.

Really good.

Jacqueline Perez: Really good. And they’re a little nutty.

Jason Plautz: Mh-hmm.

Jacqueline Perez: A lot of people just expect them to kinda taste odd or mushy because they’re a bug, but bugs are actually very versatile. To me they taste like sunflower seeds. They’re really good. I like them a lot.

Jason Plautz: The crickets carried a nice crunch and a strong earthy flavor. More nutty than gamy. But there’s still that moment of hesitation when one falls out onto the plate. Am I really gonna pop that cricket in my mouth? If this is the food of the future, I guess I’d better get used to it.

For Undark, I’m Jason Plautz.

David Corcoran: And that’s all for this episode of Undark, a project of the Knight Science Journalism program at MIT.

Special thanks this month to Jessica Eden, and extra special thanks to our podcast producer, Katie Hiler, who is moving on to bigger things. Katie has been with us from the beginning. She created the soundscape of this podcast. She put together every episode seamlessly and she rescued me from about half a million unforced errors.

Next month on the Undark podcast, we’ll have a new format. New features. A new producer. But as always, news and interviews from the intersection of science and society. Until then, I’m David Corcoran for Undark.

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1 comment / Join the Discussion

    The claim by Ms Levy that “Historically, saltwater from the bay flowed as far inland as the present-day city of Sacramento.” is simply false. There is no evidence of that. Historically the most severe salinity intrusion was in the 1930’s during a severe drought exacerbated by large scale upstream irrigation in the San Joaquin and Sacramento valleys; that salinity intrusion did not reach Sacramento nor was it close.

    Paleo-salinity data (see, for example, Malamud-Roam, F. and B.L. Ingram. 2004. Late Holocene δ13C and pollen records of paleosalinity from tidal marshes in the San Francisco Bay estuary, California. Quaternary Research 62:134-145) strongly suggest that the 1920-30s drought period had the most severe salinity intrusion into the Delta in the past several thousand years.

    It is true, as she states, that the Delta is heavily managed to maintain low salinity levels despite large scale diversions from the system for human uses.

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