Ticks are taking over the United States. Due to climate change, changing land use, and an explosion in the deer population, ticks have been expanding their territory and infecting more people than ever. They carry pathogens that cause everything from Lyme disease to the red meat allergy-inducing Alpha gal syndrome. In some cases, tick bites can be fatal.

Ticks usually lurk in the tall grass in wooded areas. That means going on a hike or even just hanging out in your backyard or a park can expose you to a tick bite. In many parts, of the country fear of ticks is changing how people live their lives, including the way they dress, how they enjoy their hobbies, or even whether they spend much outdoors at all. 

The tick surge is catching public health officials off guard. Emergency room visits due to tick bites are the highest they’ve been since 2017. In spite of the uptick, most public health departments still focus on lowering the population of mosquitos in their areas over ticks. 

Climate reporter Jonthan Mingle says we can fix this problem. As Mingle explained in a recent New York Times op-ed, encouraging the public to do tick checks and use bug spray is a part of the solution, but we’re leaving a bunch of larger interventions on the table. Mingle joined Today, Explained co-host Sean Rameswaram to explain why ticks are expanding their range and what we can do about it. 

Below is an excerpt of their conversation, edited for length and clarity. There’s much more in the full podcast, so listen to Today, Explained wherever you get your podcasts, including Apple Podcasts, Pandora, and Spotify.

We covered Lyme disease and tick bites on this show back in 2018 because the tick situation was getting out of hand. How much more out of hand has it become since then?

You know some experts I talked to used the word exponential. So what’s happening is that some of these tick species are spreading into areas where people aren’t familiar with them, doctors aren’t familiar with them. Thanks to warmer winters, ticks are expanding their hunting season. You may have a day that’s like 40 degrees in January, ticks are out looking for you, waiting for you to walk by and grab on and grab a meal. 

In 2024, a pilot named Brian Weitzel, father of three in northern New Jersey, had a hamburger, at a barbecue, went home to mow his lawn, and a few hours later was unresponsive on the floor and he died that night. His family was left in shock, of course, trying to figure out why he had died. And it turned out that he had likely been bitten by the lone star tick and had developed an allergy to red meat. This is referred to as Alpha-gal syndrome, which is just the latest entrant into the files of all the many ways in which tick bites can make us sick. The most familiar one, of course, is Lyme disease. Each year, about half a million people are treated for Lyme disease. It’s the fastest growing vector-borne disease in the US. Cases have more than doubled over the past decade, and those cases are mostly as a result of getting bitten by the black-legged tick or the deer tick. The thing is both of these ticks — and many other ticks that are also marching northward and westward and expanding their empires rapidly across North America — they can deliver all kinds of pathogens.

They’re claiming more and more of the map, and they’re claiming more and more of our psychic map right? I tell people I’m not a tick expert, although I’ve talked to a bunch of them, but I’ve become a tick expert in the sense that I am very familiar with tick paranoia and how it can keep you from venturing out into the places you love: hiking paths or picnic grounds or parks. And so that was part of the story I wanted to write about, too — Why are we letting the ticks keep us, if not out of these places that we need and love, why aren’t we fighting back?

And why is it? Are we not fighting back against the ticks?

Not really. I mean, this is one of the surprising takeaways from my reporting is that we’re barely even trying. One way of understanding that is to think about two numbers. One number is 90 percent. 90 percent of vector-borne disease cases in the US are from ticks.

90 percent?

Yeah. And yet despite the fact that 90 percent of cases of vector-borne illness come from tick bites, if you look at what local city, county health agencies do in terms of vector control, 80 percent of what they do is mosquito control, and only about 10 or 11 percent of these local health agencies around the country do any kind of tick control. So why is that? It’s a familiar story in the public health world. It’s not enough funding or policy support for trying out, testing, deploying new approaches to controlling ticks.

Even though people are dying?

We’re just kind of taking for granted that, ‘Oh, well, what can you do? You just tuck your pants in and spray some insecticide on your boots and that’s all you can do.’ It’s like, well, actually we have a long history of going to war with mosquitoes. Before there was tick control, there was mosquito control. The CDC was founded with the sole mandate in 1946 of wiping out malaria and fighting mosquitoes. 

It feels like they lost that fight because in my neighborhood you can’t go out between the hours of seven and nine o’clock.

The mosquitoes haven’t gone away, but malaria did for the most part. You know, in talking to experts today, including folks at the CDC, they told me that there’s a suite of tools we could be using if we wanted to get serious about fighting ticks. As one veteran tick expert at the CDC told me, if you want to make a dent in this problem, you have to get to the deer. The deer are the engine driving a lot of these tick species spreading, and we just have way more deer than we did decades ago, especially in the eastern US and suburban parts of America. So how do you get to the deer? I had people in the comments section of my piece saying the clear answer is just we should all be hunting deer. But in talking to the experts, they’ll tell you it’s not really a feasible solution. You would have to knock deer populations way down to make a dent in the tick populations. 

What is more promising is a combined approach of stuff like vaccines. There are people developing vaccines that you could deliver to deer or to rodents, which are another important host for these ticks so that when the tick bites them, they’ll die. That, I learned from talking to folks who do this kind of research for a living, is a more promising avenue for controlling ticks than all of us picking up crossbows and becoming deer hunters.

So why is it that we’re not doing anything?

What I heard from experts is that we’re not even funding this research in a serious way. We do this stuff for mosquitoes. People don’t realize it, but your local county health agency, they go out and they find where the mosquito breeding grounds are and stagnant pools the water and they treat it. It takes this sustained quiet effort. 

We saw the consequences of not doing that recently. This is a bit tangential, but screwworm. Screwworm was this flesh eating larval pest that devastates cattle herds that it was eradicated in the US in 1966, and it was kept at bay by the vigilance of people at USDA and USAID who ran these programs to release millions of sterile screwworm males out of airplanes. It created this wall that kept the screwworm from coming into the southern US. And probably if we stopped doing the mosquito control at a local scale, we’d see more cases of dengue fever, West Nile virus, and all these other rare but serious illnesses that climate change is making more of a threat here in the US.

Could you just practically help people understand how they can protect themselves in the absence of, I don’t know, a functional government?

Doing tick checks. And we do it in my household pretty much daily when you come home, do a thorough tick check, throw your clothes in the dryer. Ticks hate heat. And some people like to use permethrin spray, which is this insecticide that’s designed to kill ticks on your boots or your pants when you go out for a hike. Researchers have known these things are really effective if you keep doing them, if you stay vigilant. And all it takes is that one time, that one time you go out for a hike and you come back and you forget to do the tick check. 

So we need those kinds of personal measures of vigilance and protection, but we still need to kind of push for a bigger public health response to this. The ticks are going to keep spreading into the calendar, too, in the sense that as winters get warmer, more and more days of the year when you’re outdoors, you’re going to encounter ticks who are hungry, and they’re looking for you. 

The Trump administration may have just signed an agreement so controversial that President Donald Trump himself is opposed to it. 

On Wednesday, the US and Saudi Arabia signed a 30-year, multibillion-dollar nuclear energy cooperation agreement. The terms of the deal signed by Secretary of Energy Chris Wright and his Saudi counterpart have not been released, but some of the details discussed by officials in reporting by the Wall Street Journal and New York Times earlier this week raised eyebrows, mainly the fact that in addition to helping the Saudis construct nuclear reactors, the US could potentially help the Saudis construct facilities to enrich their own uranium.

The timing is particularly awkward with the US currently at war with Saudi Arabia’s rival Iran, in large part due to concerns about that country’s nuclear enrichment program. 

It is also happening in the context of an emerging new nuclear world, where last century’s arms control agreements are falling by the wayside, regimes like Russia are increasingly employing nuclear threats, and longtime US allies are increasingly nuclear-curious due to both growing military threats and skepticism about the value of American security guarantees. It could raise the risk that other countries will seek the capability to raise the bomb, even if they don’t immediately build one. 

“It’s unprecedented in the history of US nuclear policy,” said Matthew Kroenig, senior fellow at the Atlantic Council and author of the book, Exporting the Bomb. “Never before have we helped another country build a uranium enrichment facility. All the way back to Eisenhower, the deal has been: If you want nuclear energy, terrific. We’re happy to help you, but you can’t make the fuel because once you make the fuel, it’s too dangerous.”

Whether the deal will even happen is getting less clear. The agreement was already going to face significant opposition in Congress, where it must be sent for review, but Trump added to the confusion on Thursday morning with a Truth Social post that contradicted much of what had been reported the day before. Trump wrote that there would be “no enrichment of material” under the deal and that the agreement is “totally subject to Saudi Arabia joining the very respected and successful Abraham Accords,” referring to the series of diplomatic normalization agreements between Israel and a number of Muslim countries signed during Trump’s first term. This was not reported in any of the media accounts earlier in the week, which were based on statements from US officials. 

The Saudi government has not yet responded to Trump’s latest statement, but sources close to the talks have indicated that no such pledge was included in the negotiations. 

Saudi Arabia has long insisted that it will not normalize relations with Israel until the creation of a Palestinian state, and if they had caved on that position prior to the agreement, it seems unlikely that no one would have mentioned it before today. At a press briefing on Thursday, White House spokesperson Karoline Leavitt affirmed that the deal would be “off” unless Saudi Arabia joined the Abraham Accords. Asked for clarification on the discrepancy between Wednesday’s reporting and Trump’s announcement on Thursday, the White House press office referred Vox to Leavitt’s statement. 

At the moment, there’s more confusion than clarity around the deal, and what it means for the future of both the Middle East and global efforts to control nuclear weapons. 

What’s standing between Saudi Arabia and a nuke?

This idea behind the Saudi deal isn’t new: Both the first Trump administration and the Biden administration pursued a civilian nuclear deal with the kingdom. It’s been a controversial notion for just as long, given Saudi Arabia’s often aggressive foreign policy, human rights record — including the high-profile murder of US citizens — and the fact that Crown Prince Mohammed bin Salman has said in the past that his country would seek to build its own nuclear bomb if Iran ever acquired one. 

Saudi Arabia insists that its interest in nuclear energy is purely peaceful — part of a larger goal to diversify its economy away from oil and gas and to generate power for a nascent artificial intelligence industry. Proponents in the US argue that a deal would deepen ties between the US and an important security partner. It would also, they argue, head off the risk of Saudi Arabia cooperating instead with China or Russia to build a nuclear program and be a potential windfall for the US nuclear power industry. 

The US has previously entered into 29 nuclear cooperation agreements — commonly known as “123 deals” for Section 123, the legislation that governs them — involving 49 countries. The deals require countries to submit to a number of safeguards to prevent them from weaponizing these nuclear programs, including requiring US consent for any enrichment of uranium for the US-built nuclear plants. 

In more recent US deals, most countries have agreed to give the International Atomic Energy Agency even more stringent inspection authorities. Some have gone further: Under the deal signed with the United Arab Emirates in 2009 and Taiwan in 2013, the countries agreed to forswear any enrichment of uranium on their soil, including for projects in which the United States is not involved. This has been called the “gold standard” for nuclear sharing deals, and it’s what the US pushed for in previous nuclear sharing negotiations with Saudi Arabia. 

The Saudis have long balked at some of the stricter provisions in some more recent US deals, such as additional IAEA inspections and a pledge to enrich no uranium at all. The kingdom has argued these are intrusive infringements on its sovereignty, particularly given that Iran was allowed to continue enriching under previous agreements with the US. But, Kroenig said, there’s little plausible reason to oppose these restrictions if Saudi Arabia is only interested in civilian energy.

“They probably haven’t decided to build nuclear weapons yet, but it seems like they want the option,” Kroenig said.

Saudi Arabia is not going to build a bomb overnight. It’s not even going to start enriching uranium for some time. Under the deal — at least the version that was reported earlier this week by the Wall Street Journal — US companies would immediately begin work on building nuclear power plants when the deal goes into force, while US and Saudi officials would conduct a two-year study to determine “value of enrichment for Saudi Arabia.” (This, notably, would likely be concluded during Trump’s term.)

In this respect, the deal may in fact be tougher than the never-concluded Biden agreement, which reportedly would have allowed enrichment to begin immediately. 

If the study concludes Saudi Arabia needs to enrich, the enrichment facility would be constructed in a secretive “black box” to prevent the Saudis from acquiring sensitive technology. If the US objects to Saudi enrichment after the study, the Saudis couldn’t enrich for another 10 years. After that, it’s not clear what happens. 

The safeguards do not mollify many nonproliferation experts. 

“Skeptical is a mild way of putting it,” said James Acton, co-director of the Nuclear Policy Program at the Carnegie Endowment. “Even if you black-box the technology, Saudi Arabia could still nationalize the facility. This is a country that has overtly declared an interest in proliferation. Once it’s on Saudi soil, you have very limited options to stop it from misusing that technology if it decides to do so.”

The most difficult and expensive part of building a nuclear device is uranium enrichment, and the US will have helped Saudi Arabia a long way down that path. That doesn’t mean the kingdom is necessarily planning to build a bomb, but if it decides on that course of action down the road, it will have a significant head start.

“Saudi Arabia’s nuclear program does not pose a near-term proliferation risk,” said Kelsey Davenport, director for nonproliferation policy at the Arms Control Association. Rather than trying to quickly build a bomb, she suggested that “the more likely scenario is that Saudi Arabia will continue to acquire the capabilities that would be necessary to weaponize and move to the threshold of nuclear weapons, which would enable a rapid move to build the deterrent if the decision were made.”

This, she added, would both complicate ongoing nuclear talks with Iran and “set a terrible precedent” for future nuclear agreements. 

What happens now? 

“Look, there are some benefits to the deal,”  said Robert Einhorn, a former State Department special adviser for nonproliferation and arms control. “It will give a boost to the US nuclear industry. It will help cement US-Saudi strategic relations. It will deny Russia and China a foothold in an important element of the Saudi economy. But the Trump administration will have to work hard to convince the Congress and the American public that the shortcomings of the deal are not disqualifying.”

That process starts this week. The agreement will now be submitted to Congress for a 90-day review period. This isn’t a formal treaty that requires approval. Congress has to pass a joint resolution opposing it.

The deal is likely to draw opposition on both sides of the aisle. In 2019, then-Republican Sen. Marco Rubio (FL), now secretary of state, sponsored legislation that would require any 123 agreement with Saudi Arabia to be affirmatively approved by Congress.  (“I miss Sen. Rubio,” Rep. Brad Sherman (D-CA), a co-sponsor of the House version of the bill, said during a hearing on Wednesday.)

In addition to security concerns, the potential conflicts of interest around the bill may also draw scrutiny. Tom Barrack, a close Trump confidante who is now US ambassador to Turkey and an adviser on Middle East policy, was investigated by federal authorities and was the subject of a House probe during Trump’s first term for lobbying for nuclear deals with Saudi Arabia and the UAE while he had significant real estate investments in those countries and ties to the government.  

ProPublica also reported in 2019 that Barrack had sought a major financial stake in Westinghouse, the nuclear reactor builder. The Wall Street Journal wrote that Westinghouse Electric is likely to be one of the main beneficiaries of the deal to build nuclear reactors in the Kingdom.

It still seems unlikely that opponents of the deal in Congress will be able to cobble together a veto-proof majority to block it. The better question is whether Trump is effectively blocking it. If he is really going to insist on Saudi Arabia joining the Abraham Accords, that could be a nonstarter for Mohammed bin Salman. 

A new nuclear world takes shape

Events in recent years have led Saudi leaders to doubt the extent to which the US would really come to their aid in a worst-case scenario. There have been mixed reports about whether Saudi Arabia backed or opposed Trump’s decision to launch this year’s war on Iran — the Saudi government denies supporting it — but either way, if this war ends with Iran’s regime still in place, in possession of its uranium stockpile, and in control of the world’s most critical energy chokepoint, the doubts in Riyadh about America’s reliability will only increase, along with their nuclear ambitions. 

In the coming weeks, the White House will make the case that this deal is safer and more comprehensive than the ones the US would not agree to in the Biden administration and Trump’s first term. But that argument will be harder to make against the notion that Saudi Arabia’s incentive to build a bomb has only grown since then. 

In 2019, the AI researcher Rich Sutton published a short essay called “The Bitter Lesson.” Seventy years of AI research, he argued, kept demonstrating the same thing: The most effective ways to train AI rely on raw, brute-force computing power — simply scaling up — rather than clever approaches built on human insight. It didn’t matter how elegant the researchers’ work was. More compute would win every time. It’s a bitter lesson because, well, no one wants to accept that even the best efforts can go unrewarded.

This summer, climate change has been teaching its own kind of bitter lesson. Last week smoke from out-of-control Canadian wildfires reached more than 120 million Americans, sending out air quality alerts across 18-plus states from Minnesota to Virginia. Those wildfires, which were made more likely by the effects of climate change, followed record-breaking heat waves in Europe that contributed to the deaths of thousands of people.

Disasters like these inevitably renew calls for climate action, but no current US emissions policy, no amount of carbon cutting now, could clear the air, just as nothing Europe has done on climate — and it has done more than any other region, at no small cost — could protect it from those killer temperatures. Not this summer, not this decade, not the one after. The steps countries take now to reduce carbon emissions, to mitigate climate change, will not protect them from the present-day effects of climate change.

That’s the bitter lesson of climate change, and 2026 is the summer it has become unignorable. The dangerous effects we’ve been warned about are here, locked in on every timescale that matters to the people living through them. We can’t prevent the worst from happening right now, so we need to figure out how we’re going to adapt to it. 

The smoke we can’t stop

Canadian wildfire smoke is as close to an unstoppable disaster as exists today. The fires are Canada’s, the ignition is mostly lightning, the fuel is a subcontinent of boreal forest no fire agency can manage, and the whole system sits outside US jurisdiction. While strategies like prescribed burning and forest thinning can help reduce the wildfires that crop up in the western US, the sheer scale of Canadian forests makes such management far more difficult, maybe impossible. There is no timescale on which American mitigation clears American air of Canadian wildfire smoke. 

What this means is that for this wildfire smoke, at this moment, adaptation may be all there is.

American law has already conceded the point. Under the Clean Air Act’s Exceptional Events Rule, a state can petition the Environmental Protection Agency to strike wildfire-smoke days from the record used to judge whether its air is legally clean. In other words, the official response to one of the country’s fastest-growing air-quality threats is to delete it from the ledger. 

It’s true that climate attribution science ties heat waves to warming with the highest confidence of any extreme, while wildfire is messier — a compound event filtered through ignition, fuel, and fire weather. But fire seasons are lengthening, fuels are drying, and the most extreme wildfire events on Earth more than doubled between 2003 and 2023. The pattern is intensifying fire in particular regions — the boreal north among them — and the smoke goes where the wind says.

And that smoke is worse than it looks. Wildfire PM2.5 — the microscopic particles that are particularly dangerous —  is roughly three to four times more toxic to the lungs, per unit of mass, than ordinary urban particulate matter. During major smoke events, pediatric asthma visits can spike by more than 30 percent, and Harvard researchers have found the cardiorespiratory damage persists for months after the sky turns blue again. That’s especially dangerous for vulnerable populations like babies and pregnant women.

We can’t affect the winds, we struggle to stop the fires, and any current attempt to reduce warming enough to make those infernos less likely won’t be felt for years. But that doesn’t mean we’re helpless to protect ourselves from wildfire smoke, any more than we are from extreme heat.

We can purify indoor air, and it costs less than you probably think. Strap four furnace filters to a box fan — creating a Corsi-Rosenthal box — and indoor PM2.5 drops by roughly half; in testing during actual wildfire smoke, a DIY unit cut fine particles by about 56 percent in a large room and close to 99 percent in a small sealed one.

For heat, the toolkit is even better known — and one of the best proofs it works is in, of all places, France. The historic 2003 heat wave killed some 15,000 people there, most of them elderly and alone. The national heat plan built in its aftermath — tiered alerts, registries of vulnerable residents, check-in calls, cool rooms — cut the death toll of comparable heat waves by roughly 90 percent: When France hit its all-time record of 114.8°F in 2019, fewer than 1,500 died, per the Christian Science Monitor. A recent European analysis estimates a rerun of 2003 would now kill 77 percent fewer people in France than in a world that never adapted.

So technologies exist to protect ourselves. What’s too often missing are the standards, money, and the drive to deploy protection before the disaster arrives instead of after.

Catching up to today

When it comes to wildfire smoke, some governments are ahead of the game — and some aren’t. Washington state, Oregon, and California now regulate outdoor workers’ smoke exposure by air-quality index, under rules like Cal/OSHA’s wildfire-smoke standard; California funds “clean air centers” with upgraded filtration where people can shelter on bad-air days; Colorado’s Clean Air for Schools program ships free HEPA units to K-12 classrooms. A purifier humming in a classroom is essentially doing for smoke what a cooling center does for heat.

When it comes to heat, some parts of Europe are catching up. Barcelona now runs a network of nearly 400 “climate shelters” — libraries, museums, retrofitted schoolyards — with the goal of putting one within a 10-minute walk of every resident. For the first time, the city is keeping libraries open through August to do it, which, as anyone who has visited Europe in the late summer knows, is no small thing.

So adaptation exists, and it is saving lives. But this summer has also shown what happens when cities, states, and countries aren’t ready. 

In the US, the Midwestern and Northeastern states that spent last week under smoke alerts have almost none of the protections against wildfire smoke that have become more common in Western states, and no one is required to build them, because the country has no enforceable national indoor air-quality standard at all. In Europe, national heat plans are still reluctant to reach for the most powerful tool on the shelf. About one European household in five has air conditioning, compared to nearly nine in ten in the US, in large part because much of the continent still treats the machine as a moral defect. 

In both cases, rich regions that have largely taken climate mitigation more seriously than some of their neighbors aren’t pursuing adaptations they need. Which really means not taking climate change as seriously as they should. 

Accepting the bitter lesson

For a generation, adaptation was the word climate advocates were often reluctant to say out loud. In his 1992 book Earth in the Balance, Al Gore called adaptation “a kind of laziness, an arrogant faith in our ability to react in time to save our skins.” (He later changed his mind.) And in fairness, “we’ll just adapt” has often been a delaying tactic, an easy out for polluters. 

But the ground has shifted under that caution, because the projections did exactly what projections are supposed to do: they came true. 

Longer fire seasons, deadlier heat waves, smoke reaching places that never used to see it — this summer is the confirmation. And that changes what seriousness requires. If you’ve spent decades warning people that the effects of climate change are coming, you can’t treat readying for those effects as a distraction from the real work. None of this argues for easing up on emissions — each ton that isn’t emitted is adaptation nobody has to build. But preparing for what you predicted is what believing your own prediction looks like.

For AI researchers, Rich Sutton’s lesson was bitter for a specific reason. Those who resisted its conclusion weren’t foolish; they resisted it because it seemed to undercut all their hard work. They resisted it because it didn’t seem fair, just as it’s not fair that countries and states that have in many ways done much to mitigate climate change find themselves just as vulnerable, if not more so, than peers that have done comparatively little. 

But here’s the other half of Sutton’s lesson: The researchers who accepted it won. They stopped defending their cleverness and built what worked. That option is open to climate politics too. The atmosphere isn’t fair, but it is consistent, and it will deliver next summer’s version of this one on schedule. We can be ready. The bitter lesson is only bitter until you have the will to act on it. 

A version of this story originally appeared in the Future Perfect newsletter. Sign up here!

The greatest threat to animals in the US and globally is the destruction of their habitat — replacing grasslands with farms, cutting forests for timber, building suburbs atop wetlands. It’s the main reason why hundreds of species have been listed under the Endangered Species Act, which gives federal protection to species that are currently at risk of extinction or are about to be. 

That’s what makes a recent move by the Trump administration both confusing and — according to many environmental advocates — incredibly alarming. 

In a rule published earlier this month, the administration determined that, in many cases, destroying the habitat of federally threatened and endangered species is no longer explicitly illegal, even if doing so could ultimately drive them extinct. The rule upends half a century of regulatory precedent that survived many Republican administrations. Environmental advocates also say it runs counter to the very intent of the Endangered Species Act, which Congress passed in 1973 with near-unanimous bipartisan support (and which Richard Nixon signed into law).

While the Trump administration has made several recent decisions that weaken protections for endangered species — amid what many scientists call an extinction crisis — this one may have the most far-ranging consequences. Here’s why. 

A rule that could blow up the ESA

The Endangered Species Act is a complicated law, but on a simple level it makes it illegal for anyone to “take” endangered species without authorization from the government. “Take” is defined in the law by 10 different terms: harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect.

It’s the meaning of one of those words — harm — that matters most here. Up until the recent rule, the government’s definition for harm included destroying an animal’s habitat if it impairs essential behaviors, such as breeding. That might include, say, building a hotel on top of a beach that endangered sea turtles use for nesting. Such a definition was important because destroying the habitat of an already imperiled species could push it over the edge, wildlife advocates say. What’s more is that, according to the language of the law itself, the purpose of the ESA includes conserving “ecosystems upon which endangered species and threatened species depend.”

The Trump administration, however, just threw out that definition of harm and the unambiguous protection it has long afforded habitat. And while it didn’t offer a new definition, the administration said that it agrees with a much narrower interpretation of the term — articulated three decades ago in a dissent by the late conservative Justice Antonin Scalia — that only includes actions that directly and intentionally harm individual animals, such as capturing a sea turtle to eat or keep as a pet.

“For years, federal agencies abused the ESA to obstruct lawful land use and burden American families and businesses,” Doug Burgum, Secretary of the Interior Department, which oversees endangered species protections, said in a statement. “That approach turned routine activity into a regulatory trap, drove up costs that impacted people’s lives, and expanded federal authority beyond what Congress intended. This action restores common sense, respects private property, provides much-needed certainty for landowners and follows the statute Congress actually passed.” (The Interior Department declined to provide a comment on our reporting, pointing us instead to its press release and the notice in the Federal Register.) 

Under the new rule, set to take effect in September, “harm” no longer explicitly includes actions that may accidentally or indirectly doom a wildlife population to extinction. A company building luxury villas on a private beach that endangered sea turtles need for survival would not unambiguously be considered take — and thus be illegal — unless the company knew it’d crush turtle eggs or the turtles themselves in the process. Neither would logging old-growth forests that endangered birds inhabit, building wind turbines that are known to kill endangered bats, or constructing a road that would likely get endangered snakes run over. 

The administration’s interpretation of take “really completely blows up the Endangered Species Act,” said J.B. Ruhl, a lawyer at Vanderbilt University and a leading expert on the ESA.

To be clear, these sorts of actions were never forbidden outright — and this is key. An important feature of the ESA is that, with some exceptions, it allows companies, counties and states, and federal agencies to kill or harm endangered species, as long as they take steps to limit their impact. Indeed, nonfederal organizations of all kinds have, for decades, received federal permits that allow them to “take” endangered species, in exchange for coming up with a plan to minimize the harm they may cause. In Hawaii, for example, an electric utility that operates power lines that can injure endangered birds takes steps to prevent collisions and funds an avian rehab facility that helps offset some of its impacts. 

The problem now is that these conservation plans — which wildlife advocates say are critical for species recovery — are rooted in the defunct definition of harm, according to Daniel Rohlf, a law professor at Lewis & Clark Law School. 

The whole purpose of these so-called Habitat Conservation Plans is to lessen the incidental, or accidental, impacts on endangered species, while at the same time allowing companies to still build and operate legally. But in rescinding the former definition of harm, the Trump administration has essentially just said that all that incidental killing is no longer illegal anyway. That may undermine future Habitat Conservation Plans and those that have yet to be finalized. This “pulls the rug out from under literally decades of work,” Rohlf said of the recent rule. 

Next up: The Supreme Court?

Even under the new rule, the ESA still has some important protections for habitat. When the government lists a species as threatened or endangered, for example, it usually designates what’s called “critical habitat” — areas that it deems essential to the survival of the species. Under the ESA, all federal agencies have to ensure that their actions, such as permitting new mines or wind farms, do not destroy critical habitat or jeopardize the existence of a species. Those responsibilities are still intact. 

It’s also not certain that the new rule will stick. Several environmental groups have already sued the administration to try to reinstate the former definition, alleging, among other claims, that rescinding the definition of harm violates the language and the intent of the ESA. This challenge is likely to reach the Supreme Court, Ruhl says. 

To understand what could happen next requires some important context.

Until two years ago, courts typically deferred to federal agencies to determine how to interpret ambiguous language in laws like the ESA. This legal principle was known as the Chevron doctrine. It was the Fish and Wildlife Service, for example, that published a rule decades ago clarifying that the ambiguous word harm includes destroying an endangered animal’s habitat. That interpretation survived a famous 1995 Supreme Court case, Babbitt v. Sweet Home Chapter of Communities for a Great Oregon, in which Oregon landowners and the timber industry argued that the government defined “harm” too broadly. The court decided that an “ordinary understanding” of that term “naturally encompasses habitat modification” that injures or kills endangered species.

In the summer of 2024, however, the Chevron doctrine was overturned. That means the power to interpret unclear language in laws now rests with the courts. 

The Trump administration has seized on this fact, Rohlf said. Instead of redefining what harm means, the administration simply axed the existing definition that included impacts to habitat that injure wildlife. It will now be up to the courts to decide what is considered harm in future cases brought under the ESA — such as if, say, an environmental group sues a developer, claiming that it destroyed essential habitat for an endangered species in violation of the Act. The administration did not stop short of making clear what it thinks: In the preamble to the rule, it said harm should only include actions made directly and intentionally against endangered organisms.

Wildlife advocates point out that the Supreme Court already determined that a definition of harm including habitat destruction is reasonable. That’s what Babbitt v. Sweet Home was about. But because that case rested, in part, on the now-overturned Chevron doctrine, the courts — and perhaps eventually the Supreme Court — may relitigate the meaning of harm. (The Supreme Court did make it clear that it won’t call into question decisions that relied on the Chevron doctrine before it was overturned.) 

Ultimately, it’s hard to argue that harming an endangered species, in a plain reading of the word, does not include destroying vital habitat that it needs to survive or other actions that kill or injure them indirectly, legal scholars told me. It’s also clear that Congress saw it this way when it wrote the law. There’s a whole section of the ESA about granting permits for “incidental take,” which could include damaging an animal’s habitat, according to Holly Doremus, a law professor at the University of California, Berkeley. That section only makes sense, she says, if you’re interpreting harm to include actions that accidentally and indirectly kill or injure species — which is far broader than the definition that the Trump administration would like to use.   

For the Trump administration to really get what it wants, Doremus said, it would need to remove the word “harm” from the ESA altogether. Short of that, she said, Trump officials “want to make ‘harm’ as ineffective a statutory term as possible.”

Should the administration succeed — should the courts determine that “harm” does not apply to destroying the habitat of endangered species — environmental advocates warn that the ESA will lose much of its extinction-preventing power.

“If this decision is allowed to stand, it eviscerates the statute on which imperiled species conservation has rested in this country since 1973,” said Jane Davenport, a senior attorney at Defenders of Wildlife, an advocacy group. “This is truly a stake through the heart of the ESA.”