December 11, 2024- The United States Fish and Wildlife Service recently proposed to list Monarch butterflies under the Endangered Species Act due to habitat loss, pesticides, and climate change.
- Milkweed, the only plant monarchs lay their eggs on and a critical food source, is essential to their survival.
- River Partners has set an ambitious goal to plant 15 million milkweed plants across California by 2030 to support Western monarchs and other pollinators.
- Heritage Growers, River Partners’ native seed farm, will provide milkweed seeds and rhizomes for the monumental effort.
Monarch butterflies, once a common sight across North America, are in peril. This week, the U.S. Fish and Wildlife Service proposed to list monarchs as a threatened species under the Endangered Species Act, citing habitat loss, pesticide use, and climate change as the primary drivers of their decline.
For the Western monarch population—one of two main populations who migrate between the California coast and Rocky mountains— early-season surveys by the Xerces Society from November 2024 observed fewer than 7,000 monarchs overwintering along California’s coast. This is a stark contrast to the approximate 4.5 million observed in the 1980s, but slightly better than when the population crashed below 2,000 individual butterflies in 2020, marking a catastrophic 99% decline.
Without swift and large-scale restoration, these iconic pollinators could vanish forever.
A Bold Plan for Western Monarch Recovery
River Partners is taking bold action to restore habitat for Western monarchs and other imperiled pollinators with a new goal to establish 15 million milkweed plants by 2030 in priority areas across California.
“We are well positioned to do this work,” says River Partners Associate Director of Science Michael Rogner. “The listing of monarchs will spotlight our plan to scale milkweed restoration efforts in California.”
Starting in 2020, River Partners has been on the front lines of monarch recovery, implementing the largest coordinated Western monarch recovery to date. Partnering with the California Department of Fish and Wildlife, Xerces Society, Monarch Joint Venture, and Washington State University, River Partners planted over 30,000 milkweed plants across 600 acres in priority restoration zones statewide.
The results were clear: when we established milkweed, monarchs and other pollinators returned.
Now, River Partners is scaling up its efforts exponentially—by nearly 50,000%—to achieve our 15 million milkweed goal by 2030.
How? By incorporating milkweed and other forbs, or herbaceous flowering plants, in new restoration as well as augmenting suitable restoration sites in priority areas to support pollinator habitat. Western monarchs migrate east over three generations from coastal California to the Rocky Mountains, traveling along critical riverways that provide food and shelter. Then, a single generation makes the incredible journey back to the California coast, where the cycle starts again. Our goal is to ensure monarch and other imperiled pollinators have access to flowering nectar plants and suitable breeding habitat along the way.
Eastern monarchs undertake a similarly awe-inspiring migration, traveling thousands of miles from as far north as Canada to overwintering sites in the forests of central Mexico. Like their western counterparts, they depend on milkweed and nectar plants along the way.
Together with our partners, we can turn this bold dream into a reality—and not a moment too soon for monarch butterflies.
“Habitat restoration is a key action to help monarchs and other imperiled pollinators,” says Rogner. “But the scale of habitat loss requires us to go much further, much faster.”
Why Milkweed Matters
Monarchs depend on milkweed, the only plant where they lay their eggs and the primary food source for caterpillars. Milkweed and other pollinator-friendly plants commonly grow in riparian landscapes, which means riverside habitat are essential migration corridors for monarchs. Monarchs follow the blooms of nectar-rich native plants along their migration routes and require access to water and shaded places to rest.
However, over 95% of riparian habitats have been lost since colonization in California. Restoring riverside corridors with milkweed and other native pollinator plants is an essential strategy to help monarchs and other imperiled pollinators.
“Our goal is to increase pollinator resources year-round,” Rogner explains. “We carefully select plant species adapted to the specific timing and conditions of monarchs and pollinators on each restoration site, whether it’s Northern California’s Butte County or far-southern Imperial Valley.”
We’ve learned just how quickly monarchs and pollinators can recover when milkweed and other essential pollinator plants are restored by studying our past work. Across nearly 600 acres on eight riverside sites River Partners restored in the largest-to-date monarch recovery effort in the West, pollinator abundance and richness increased over the first three years as plants took root and blossomed. Through regular monitoring in partnership with Xerces Society, we discovered the sites provided habitat for 21 species of declining or imperiled butterflies including monarchs, and even imperiled bees.
“Monarchs were observed at six of the eight sites and eggs and larvae found at four of those sites,” River Partners Restoration Science Ecologist Haley Mirts said. “Not only did the project benefit the monarch butterfly, but it also created habitat for at least 31 butterfly species, 21 of which have been designated as declining or imperiled.”
Monarchs were found on restored areas where they had not been seen prior to restoration, according to Dr. Angela Laws, Endangered Species Conservation Biologist with the Xerces Society. Yet, we only were able to monitor our sites for a few days each summer due to limited funding. The listing of monarchs can hopefully help expand survey efforts and answer deeper questions about exactly how and when monarchs are using riparian areas, so we can inform our approach to restoration.
River Partners’ ambitious goal to restore 15 million milkweed plants in priority areas for Western monarchs builds on lessons learned from years of restoration work. By collaborating with key allies like Heritage Growers, River Partners’ native seed farm, we can produce enough milkweed seeds and rhizomes (roots for propagating) to restore locally adapted milkweed to California’s diverse landscapes.
“It’s going to take a lot of seed, but we’re up for the challenge,” says Heritage Growers General Manager Pat Reynolds.
The Center for Biological Diversity estimates that 1.5 billion milkweed plants are needed across North America to restore 100 million acres of habitat for monarch recovery. Based off that calculation, River Partners estimates 15 million milkweed plants are needed in California alone for monarchs.
A Symbol of Hope
Despite the grim statistics, there’s reason to hope. Insect populations, while vulnerable, have an incredible capacity for recovery.
“Insect populations are really variable over time—but that means they can also bounce back from declines,” says Laws. “It’s something we could see recovery with more quickly than with longer-lived species like whales. It’s scary when we see their populations crash, but we know they do have the capacity to recover—if we act.”
Restoring monarch habitats also benefits countless other pollinators, from native bees to imperiled butterflies. As Dr. Sarah Gaffney, Associate Restoration Scientist at River Partners, explains, “Pollinators in general are declining, but monarchs are the flagship species because they’re declining so much more rapidly. Yet when we restore monarch habitat, we’re also supporting an entire ecosystem for pollinators.”
During the final walk through at Upper Butte Basin Wildlife Area in Glenn County, one of the eight sites where we restored milkweed, the hope of restoration was tangible. River Partners team members and project funders watched in awe as a monarch butterfly zoomed across the site, laying eggs on the milkweed planted just months earlier. Moments like these reinforce just how quickly nature responds when we create conditions for recovery.
Join the Movement
Everyone can play a role in saving monarchs:
- Plant milkweed: Xerces Society offers resources for pollinator conservation in California and free Monarch and Pollinator Kits for large-scale land. Heritage Growers is proud to partner on the kits to provide plants.
- Reduce pesticide use: Pesticides are a significant threat to monarchs and their habitats.
- Support restoration efforts: Donations to organizations like River Partners directly fund habitat restoration to save monarchs from extinction.
Together, we can ensure that monarch butterflies remain a symbol of resilience and hope for generations to come.
