Hope for Monarch Butterflies: New WWF Report Finds 64% Increase
Good news is hard to come by in the conservation world—but this week, we have some to share. A new report from WWF‑Mexico shows that the endangered migratory eastern monarch butterfly is showing promising signs of recovery, with monarchs occupying 7.24 acres of forest in their wintering grounds in Mexico—up from 4.42 acres last year. That’s a 64% increase.
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In this episode of Nature Breaking, we revisit conversations with two monarch experts—Eduardo Rendón‑Salinas of WWF‑Mexico and Court Whelan of Natural Habitat Adventures—to explain why this rebound matters, how monarch populations are measured, and what challenges still lie ahead. From the butterfly’s amazing multi‑generational migration that spans thousands of miles to the threats posed by habitat loss, pesticides, and climate change, this episode dives into one of the most extraordinary natural phenomena on Earth.
If you’re looking for a rare bit of optimism—and a reminder of why these butterflies inspire wonder across North America—this episode is for you.
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TRANSCRIPT:
Seth Larson: If you're tired of bad news when it comes to nature, then this episode is for you. Last week we found out that the endangered migratory eastern monarch butterfly is showing promising signs of recovery. A new report from WWF-Mexico estimates a nearly two-thirds increase in the species population compared to the same time last year. Stay tuned to learn more about this hopeful news and why all of us should care about it.
Welcome to Nature Breaking, a podcast from World Wildlife Fund. I'm Seth Larson, and today we have an update about a beloved species that we've covered before on this show: Monarch butterflies.
We devoted episodes of this show to monarchs in both 2023 and 2025, so you may remember that migratory eastern monarch butterflies are remarkable, not just for their iconic black and orange colors, but for the incredible journey they embark on each year from Canada and the United States down to Mexico to spend the winter and then back again.
Sadly, these butterflies were officially classified as endangered in 2022 and each year WWF partners with the government of Mexico and local communities at the country's Monarch Butterfly Biosphere Reserve to monitor butterfly populations. The report from this year's survey was just released and the news is encouraging. Monarchs occupied 7.24 acres of forest in their hibernation grounds in Mexico compared to 4.42 acres the previous winter, that's a 64% increase. To be clear, the eastern monarch population has been trending downwards for years, and this latest finding is still far below the long-term average.
So rather than a call for celebration, this report serves as a reminder that progress is possible, but that we need to redouble our efforts if we want to keep seeing that progress continue. With that in mind, I want to share some excerpts from our previous episodes on this topic to remind all of us what makes monarchs so important, what conservationists are doing to help them, and what lessons we need to carry forward into the next monarch migration season.
Before we begin, please take a moment to rate this show and subscribe to our feed on Apple Podcasts, Spotify, and YouTube. Thanks for tuning in and here's our episode.
As I said in my intro, I previously interviewed two amazing experts on monarch butterflies, so I want to let them do a lot of the talking in today's episode. And I like to start every conversation about monarchs by sharing the amazing story of their journey across the North American continent each year. Here's how Eduardo Rendón‑Salinas, a monarch butterfly expert from WWF-Mexico described the start of their journey when we spoke in 2023.
Eduardo Rendón-Salinas: When the monarchs overwintering here in Mexico and the spring arrives to these grounds, monarchs go back to the south of the United States. Because in that moment they can find asclepias or milkweeds in the south of the states, particularly Texas. And then all monarchs that survivorship here in Mexico to the overwintering time back in the spring migration to the states, particularly Texas, and then they lay the eggs in the asclepias, in the milkweeds. And then a new spring generation is generated there in the states. In fact, there are two generations of spring there in the south of United States. Later, the third generation migrate to the north and establish two new generations in the center and north of United States and Canada.
Seth Larson: Of course, once these butterflies reach that northern edge of the migration and after several generations have passed where they were born, kept flying north, laid eggs, died, another generation was born, and they did it all over again, eventually they have to return to Mexico. And that generation that makes that journey lives not just a few weeks to a month, but upwards of eight months. Here's how Court Whelan, Chief Sustainability Officer at Natural Habitat Adventures, described the journey of this so-called super generation when we spoke in 2025.
Court Whelan: So let's start the year in late summer, early fall. Now this going to differ based on latitude. A butterfly in Maine is going to start its migratory phase a little bit earlier than one in the southeast or in Texas, somewhere in the middle for those in Maryland and Kansas, et cetera, et cetera. Let's just, for the sake of it, let's just say August. The August monarch butterfly.
Very often it is roughly around that time of year that the adult butterfly gets these cues from the environment. It's decreasing day length, it's lowering temperatures, there's their host plants, their milkweeds start to senesce and die, and they cue in on the angle of the sun, believe it or not. When that sun angle gets below a certain degree level above the horizon at noon, yes, believe it or not, it's that specific, they turn on these migratory genes more or less.
And then they begin to fly and they begin to navigate using the same sun, using various other cues down toward Mexico. That butterfly in general will make a 2,000 to 3,000 mile journey, all the same individual, going across the Great Plains, going through Texas, going through Northern and even Central Mexico, tanking up on nectar along the way. That's what they need to feed.
Seth Larson: Hope they take a few rest breaks along the way.
Court Whelan: They do take a few rest breaks. We know of a few spots routinely that they will overnight, they'll take refuge from storms and all that. But then usually around the Day of the Dead, so November 1st and 2nd, we start to see the monarchs arrive in their winter home, which is Central Mexico and the high Sierras, the Sierra Madres. And this is indeed high elevation, we're at like 10 and 11,000 feet. And then that butterfly roosts on these towering Oyamel fir trees for the next four and a half-ish months until about middle of March.
Seth Larson: It is during that stretch from November to March that WWF partners with the government of Mexico and local communities to analyze the annual butterfly population in the Monarch Butterfly Biosphere Reserve. We do so by measuring the total area of forest occupied by hibernating monarchs. It's a painstaking process that Eduardo described for me in 2023. Here he is again.
Eduardo Rendón-Salinas: To monitor the colonies of the monarch, we go every day since November. Two times every month to the sanctuaries. And when we find colonies, we measure the surface occupied by the groups of monarchs. Obviously, we measure the surface of each of these groups. And then we use a compass and a topographic flag. And then first of all, we make the position, geographical position of the colony using the tree that is highest in the particular slope. We take one single point about the geographical position, and then we measure the position of the next tree with monarchs, with the compass and with the flag. And then the other, the other, the other. Then we take the polygon of the colonies that are using monarch with the groups in the branches and in the trunks.
Seth Larson: Wow.
Eduardo Rendón-Salinas: And later we go to the geographical system of information and we calculate the surface of each colony every season, two times every month.
Seth Larson: So that's how we arrive at these estimates each year, and as I said earlier, even though we got some really good news this year, and in fact the previous year as well, this population of monarchs is still considered endangered. So what's been causing their decline in recent decades?
There are multiple factors, but two big culprits have been climate change, which brings more extreme weather that makes the monarch's journey all the more difficult, as well as the loss of milkweed across their migration area. Milkweed is the only plant on which they'll lay their eggs and the only source of food for baby monarch caterpillars. But milkweed has been vanishing across North America due to the use of herbicides and pesticides, as well as land use change, and other factors. Here's how Eduardo summarized the threats facing monarchs in 2023.
Eduardo Rendón-Salinas: In 2021, we publish, a group of researchers, we made an analysis about what are the big causes or factors that influence the declining of the monarch? And we can determine that since 1994 to 2003, the most important factor that affect the monarch population and determine the declining was the use of herbicides and pesticides, particularly herbicides in the corn and soy grounds in the Midwest of the United States. The farmers are using, was using Roundup or glyphosate in general, to eliminate the milkweeds, the plants where the monarch eat when they are larvae. So they eliminate about 81% of the plants in that lapse of time.
Later from 2004 to 2018, we discovered that the climate, the variation of the climate in the reproduction sites in the summer, in particularly in United States, was the responsible of the declining. So we have currently two big factors of the monarch declining.
And the other factor that is important obviously here in Mexico is the forest degradation, sometimes deforestation and other, simply, degradation of the forest.
So there are more factors, but now we are very clear about the use of herbicides since 1994 to 2003 is the responsible and 2004 to 2018 the climate change is responsible of the declining of the monarch.
Seth Larson: Despite those challenges, we've seen that progress is possible, right? And one thing that helps is planting milkweed. Millions of people have gotten involved in that in recent years, planting it in their yards, in their neighborhoods and their communities. But at the end of the day, why should we all care about saving a tiny butterfly species so much? I asked Court that question last year, and I think his answer is a wonderful note to end on.
Court Whelan: The monarch butterfly is essentially an umbrella species in some ways. If you conserve the monarch butterfly and the habitat it needs in Mexico, you are saving people. You are saving forests, you're saving a habitat for so many other critters. Monarch butterflies are great pollinators, and we get 80% plus of our food in the United States and really just North America in general from pollinators. So saving natural pollinators is a huge thing. But then there's also something a little bit more philosophical and abstract that, when there is something that so many people love, so many people want to see flourish, we should try to save it for its own sake, simply because we love it or someone in our family loves it. And I think that we're often very much trained in the world of conservation biology to create that justification and talk about things like pollination and all the ecosystem services, because those have demonstrable, like legit numerical values. But in some cases, I think we have to look at what do we really love in the world and what still gives us a sense of wonder and awe? What baffles the mind? What leads to new scientific discoveries beyond just the critter being studied? And the monarch checks all those boxes.
Seth Larson: Okay, that's a wrap for today's episode. Amid all the doom and gloom in the world, I hope the recent news about monarch butterflies rebounding gives you a little bit of hope for nature. And if you want to be a part of helping to keep the momentum going, please consider adding milkweed to your list of springtime seeds to plant. I'll include a link in our show notes about the right kind of milkweed to plant for your specific region. For now, thank you for listening and together let's keep building a more sustainable future.