A recent U.N. panel on biodiversity reported that there are one million species currently threatened with extinction. Most of those are the insects that make up two-thirds of the earth’s species. What we know about these vanishing insects is largely informed by scientific studies that show the alarming, decades-long decline of butterflies, including those listed under the Endangered Species Act.

As a conservation biologist, studying these butterflies has been my life’s work, and I am deeply troubled by the disastrous modifications to the Endangered Species Act recently announced by the Trump administration. Indeed, the changes could jeopardize one of the act’s signature successes: that no listed butterfly has yet gone extinct.

I began studying rare butterflies when I was a junior professor in 2001. At that time, government agencies and conservation organizations were struggling to develop conservation plans for an endangered butterfly, the St. Francis’ satyr (Neonympha mitchellii francisci). They asked me to bring my expertise to the effort and I enthusiastically embraced the opportunity. As a naive overoptimist, I thought that my scientific expertise was just the ingredient needed to promote the insect’s rapid recovery.

On starting my research, my first course of action seemed obvious and I kept people out of the St. Francis’ satyr’s habitats. This was not hard to do, as the butterfly lives in the mucky wetlands of the Fort Bragg army installation in North Carolina, alongside streams that few humans ever enter.

In 2005 I observed the loss of one St. Francis’ satyr population. I chalked this up to natural loss that could be offset by gains elsewhere. Then there followed losses in 2006, 2008, 2009 and 2010. There were no gains. By 2011 there remained only one population of St. Francis’ satyr for me to study.

I was alarmed, but took some comfort knowing that there was another set of populations that lived in an unlikely refuge: the artillery range. Because of daily bombardment with heavy artillery, the U.S. Army strictly prohibited access to these areas. But they made an exception for me, on behalf of these butterflies.

As I entered for the first time, I was astonished to observe a great paradox about artillery ranges. They were the opposite of the moonscape I expected. The forests and wetlands were astounding. During that first visit, I observed the largest populations of St. Francis’ satyrs that I had ever seen.

The butterfly’s habitat requires fire to keep the trees at bay, and beaver to create new wetlands. Counterintuitively, the intense and frequent disturbances caused by artillery were not, after all, harmful to the butterflies. Quite the opposite: projectiles, flares and machine-gun bullets ignited fires and simulated the natural disturbance that kept their wetlands open and grassy.

Witnessing this forced me to admit that nearly every measure I had taken to conserve the habitat of the St. Francis’ satyr outside the artillery ranges had been wrong. My lab’s actions had protected the butterflies from direct harm. But by doing as little as possible, we were, in fact, pushing the butterflies closer to extinction. If the artillery ranges did not exist, the butterfly would be extinct today.

So I set a new course in our restoration efforts. In a small area about the length of a football field, we created temporary dams to flood wetlands and hauled out trees to let in sunlight. Soon afterward, the butterfly populations rose to hundreds of individuals, representing about a quarter of the worldwide population of St. Francis’ satyr. The Endangered Species Act had inspired a partnership between the army, scientists, and conservation agencies that was essential to supporting this butterfly’s recovery.

Like the St. Francis’ satyr, the 25 butterfly species that are currently listed as Threatened or Endangered under the act have already descended to the verge of extinction. Their numbers are so small that if you gathered up all the living individuals of any of particular species, such as the world’s 3,000 St. Francis’ satyrs, you could hold every one of them in your two hands. Threatened species are no different. The act is the only thing keeping them from extinction.

One way that the announced modifications to the Endangered Species Act will harm butterflies is to deny any present effects of climate change, despite evidence that this is already threatening butterflies with extinction. The Miami blue butterfly, for example lives on tiny islands near Key West, Fla. Nestled between dunes just beyond the beach, the total Miami blue habitat occupies the area of about a nine-hole golf course. In a large fraction of this small range, sea-level rise has already eaten away 50 percent of their habitat.

The Bartram’s scrub hairstreak butterfly also lives in South Florida, and one of its two remaining populations was in the path of Hurricane Irma’s eyewall. No butterflies of this species have been seen there since Irma struck. It is already too late to reverse climate change’s effects on these species, but with support from the Endangered Species Act, habitat can be managed to make it more resilient to climate change, and butterflies can be moved to higher ground.

Endangered butterflies are the proverbial canaries in the coal mine for insects, by far the most diverse species group on our planet. Butterfly declines and extinctions are near-certain indicators of unobserved extinctions in all other insects.

Take, for example, the western monarch that overwinters on the California coast. In just a few decades, its populations have plummeted from millions to just 28,000. This decline now places the western monarch alongside the world’s rarest butterflies. And this butterfly, now en route to almost certain extinction, has yet to be listed as Endangered. Were the western monarch to be protected under the Endangered Species Act, conservationists could prioritize preserving and restoring its overwintering and breeding habitats and interagency partnerships, like the one that supports the St. Francis’ satyr, could bring it back from extinctions’ brink.

With every passing year, I wonder whether I will see the last of the rarest butterflies listed under the Endangered Species Act. Their numbers and ranges are so small, and the threats to their survival are so high, that my encounter with the last butterfly is a real possibility. If the most common butterflies such as monarchs can fall so far and so fast, what butterfly is safe from possible extinction?

There is still time to reverse course and save the rarest butterflies from extinction. Real recovery can be achieved for the earth’s biodiversity. But what I have learned in studying butterflies is that conservation takes a better understanding of species’ biology, natural landscapes, and often unexpected natural forces, and scientists are reliant on the protection of legislation like the Endangered Species Act to make this evidence-based restoration work worthwhile.