Brian Lehrer: Brian Lehrer on WNYC. After a lot of heavy stuff on this September 11th, let's end the show today with one of our periodic looks at the ways even in a major metropolitan area like this one, with all the people and cars and buildings, we urban dwellers intersect with the natural world in unexpected ways. Like the world of monarch butterflies. Those visually striking orange and black beauties that you may have noticed pass through here this time of year. It turns out they're in trouble, so much so that the Biden administration proposed designating them as a threatened species under the Endangered Species Act. Benji Jones, a senior environmental correspondent at Vox, reports that New York City is doing its part to feed and shelter them in small ways to that can add up. This is one place that anyone with a tiny garden plot can make a difference, so listen up if you have one. He's here to tell us more about the butterfly, its mind-blowing migration, and how city and suburb dwellers can help it on its way. Hey, Benji Jones, welcome to WNYC.

Benji Jones: Hey, Brian, thanks for having me and letting me talk about bugs.

Brian Lehrer: Yes, and not the usual kinds of bugs we talk about. Could you start with the thing about monarchs that brings them to this area every year, their crazy migration?

Benji Jones: Yes. Usually when we think about, or when I think about animals migrating, I'm thinking about birds or caribou or whales, big creatures. Monarchs, too, have these incredible migrations, some of the most incredible migrations in the animal world. You'll see that across much of the US, especially east of the Rocky Mountains, the monarchs that are summering there migrate in the fall down to one forest in Mexico, so really in central Mexico, near Mexico City.

All of these monarchs, hundreds of thousands of them, are going to the same forest to overwinter. They're doing this hibernation. Then come springtime, they migrate back up to northern parts of the US and even into southern Canada, and that's when we start to see them in New York. The monarchs that we're seeing in New York actually came from Mexico, but one of the most interesting things about their migration in the springtime is that they do it over multiple generations. A monarch that is leaving from Mexico after it's overwintered will go into the southern US, lay eggs, and die.

Then the next generation picks up the next leg, moving northward, and they'll do this over two to four generations. It's like an intergenerational relay race. What we see in New York City is the monarchs in the summertime, usually, and just in the coming weeks, they're going to start moving back down to Mexico, and that will take several weeks, and it's just one generation to go to Mexico, but they're making this massive journey. It's really incredible.

Brian Lehrer: Are you saying that these tiny little butterflies can fly all the way from Canada to Mexico?

Benji Jones: Yes. They don't all make it. There are a lot of obstacles, as we'll talk about. They need a lot of nectar resources, so native flowers, obviously, storms can be a problem, traffic can be a problem, but yes, there are a lot of monarchs that are going to end up making it all the way to Mexico, which is over 2,000 miles in some cases. It's remarkable that something as delicate as a butterfly can make that journey.

Brian Lehrer: Listeners, anybody want to say or ask anything about monarch butterflies? Are you seeing many monarchs this year? Do we have any butterfly gardeners out there? Have you planted anything specifically for local wildlife? Birds, bees, butterflies, or just why you love monarch butterflies, as so many people do? 212-433-WNYC. Call or text. 212-433-9692 for Benji Jones from Vox. I mentioned that President Biden proposed threatened status, as it's called, for the monarch butterflies. How threatened a species are they?

Benji Jones: What we're seeing, it's really hard to study the population of monarchs because they're so dispersed across the country. There are obviously a lot of them. It's difficult to count them one by one. The way that scientists estimate how their population is doing is they look at the overwintering sites in Mexico. This one forest, this fir forest near Mexico City, and they count the number of acres over which monarchs are clustering around these trees. There are so many monarchs that the branches are literally drooping with the weight of the monarchs.

What they're seeing is that over time, we're seeing a decline in just the acreage over which you see monarchs clustering on trees in this forest. Fewer monarchs are making it to Mexico, and that's really what has raised an alarm for the population overall. It's a pretty dramatic drop off. There were monarchs over about 21 acres, an average of about 21 acres for the first 10 years of monitoring, which was '93, I believe, to 2002. Then just this past winter, there were only monarchs over 4.4 acres. A dramatic decline in the number of monarchs that are overwintering in the Mexico site.

That is the bulk of the North American population. That's why they're like, "Okay, there's a problem here." They know that there are reasons to be concerned and reasons to know that they're declining. Other than just the population dip, we see a loss of their habitat across the Midwest, across places like New York, and that is an obvious reason for why they're declining.

Brian Lehrer: Is that habitat largely milkweed?

Benji Jones: Yes, that's a big part of it. Especially in the core of their breeding range, which is the Midwest. Like Iowa, Missouri, Nebraska, Kansas, you saw in the late '90s, early 2000s, this just massive spread of herbicide glyphosate, and that herbicide used on corn and soybean fields primarily killed so many milkweed stems, like hundreds of millions of milkweed stems. Milkweed is essential for monarchs because it is the only plant that their larva, the caterpillars, can eat. They need milkweed to survive.

Brian Lehrer: Of course, milkweed was seen as a weed. That's how it got its name. You visited a number of parks and fields where they're deliberately planting milkweed and other native butterfly-friendly plants. Do you know if there's data on how many home gardeners are opting for native plants over more ornamental ones? We might call them.

Benji Jones: Yes, that is a great question, and it is something that I tried to figure out. I wanted hard numbers on this, and I couldn't find them. What I gleaned from my reporting and talking to a number of folks is that there has been, not necessarily a clear-- Like it's not clear in terms of data of the number of people that are planting native plants. What you see is there's this movement across New York, across the state, across the country, to plant more native plants in lieu of these non native ornamentals. You see, obviously, things like daffodils and tulips all across the city.

Those are beautiful, but they don't have as much value for native pollinators like monarchs, and so you're seeing people start to understand. It's clicking for folks that if you plant native plants, they're going to draw native insects, the native insects are going to draw native birds. It anchors this ecosystem. Even if you have a small space, a stoop, a backyard, you can actually do a lot to help the ecosystem.

Brian Lehrer: Theresa in Harrison in Westchester, you're on WNYC. Hi, Teresa.

Teresa: Hi, how are you doing? Yes, monarchs, I'm a fan. In my backyard for years, I've been planting stuff to attract the butterflies and the bees. For years, it was very grim. I would only have one little monarch showing up, and it just hurt my heart so much. I just kept planting stuff, and I have these butterfly bushes that have just popped out of the cement and are growing. This year, I call it an epic amount of monarchs. I had about eight of them, and compared to the past, oh, nine years, it was, I call it, an epic windfall of monarchs.

We just recently had a horrible rain windstorm. The next day, I was like, I think it devastated the monarchs, but you know what? They started slipping back in again. They're definitely fewer. I'm doing everything I possibly can to plant stuff, but I have not had luck with milkweed.

Brian Lehrer: Teresa, thank you very much. It sounds like you are definitely doing your part as a very intentional gardener with the monarchs in mind. That's awesome. Elmo in Bergen County, you're on WNYC. Hi, Elmo.

Elmo: Hey, how are you? I love your show.

Brian Lehrer: You make me late to work every day, but that's okay. I'm a beekeeper, I'm a zoologist, and I have planted a lot of butterfly bushes, but the problem is they love milkweed, and that is a wetland thing. Other question for your guests. What other sustainable nectar-producing plants can one plant on one's property in Bergen County or Rockland County or Westchester County, or even New York City? What do you suggest?

Benji Jones: Yes, okay. That's a good question. There are several different varieties of native milkweed, and so I would look up to see which one might be more suitable to your type of how much sunlight you're getting, how wet the soil is. Swamp milkweed, for example, might need wetter soil. Common milkweed, which caterpillars love, not so much. There are a ton of different other varieties of nectar plants. Like New York ironweed's a good one. There's cluster mountain mint is a good one. All kinds of asters, sunflowers.

You really have a large variety. The good thing is that nurseries around the state are starting to carry more native plants. Just trying to find native plants to put in the ground is much easier than it used to be. There are a ton of resources online that I recommend you check out. Xerces Society is a great, great place to start.

Brian Lehrer: We're going to run out of time soon. Another listener has two questions. I wonder if you can address them very briefly. One, is it helpful to hand-rear monarch caterpillars? Do the chemicals given to greenhouse plants hurt the monarchs?

Benji Jones: Chemicals, yes, they hurt the monarchs. You should always try to avoid herbicides or pesticides. Whether it's you spraying them or the nurseries using them or them being embedded in the plant tissue, they're a problem. Hand rearing is okay. I've done it myself. I love it. It's a way that people connect with nature. From an education perspective, it's really, really great. It can have some negative effects if you're rearing them at home because they're not getting the same sorts of cues, especially if they're going to be migratory.

They're going to migrate to Mexico. It's always better to focus on creating habitat for them. In terms of educating the public, having a connection to the natural world, rearing them at home, is good.

Brian Lehrer: Last thing. 20 seconds. Does it matter at all besides that we like to look at butterflies? Lanternflies are cute, too, but we step on them on purpose. Do monarchs play a bigger part in the ecosystem, in addition to how we like them aesthetically? 20 seconds.

Benji Jones: They're not fantastic pollinators. They do pollinate, but to a small degree, things will eat them. They're playing a role in the food chain. More importantly, the milkweed that supports monarchs and the other wildflowers that support monarchs, that people plant because they want to see them, those plants support all kinds of other native insects. By supporting monarchs with their habitat, you're supporting the entire native ecosystem. From that perspective, they are much more useful than lanternflies.

Brian Lehrer: Benji Jones, senior environmental correspondent at Vox, where he will soon publish a new story about monarchs and the city. Thank you so much. This was great.

Benji Jones: Thank you, Brian.

Brian Lehrer: That's The Brian Lehrer Show for today, produced by Mary Croke, Lisa Allison, Amina Srna, Carl Boisrond, and Esperanza Rosendaum. Juliana Fonda and Milton Ruiz at the audio controls. Stay tuned for All of It.

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