The National Park Service has removed 92 documents on climate change from its website. PDFs describing the agency’s “Climate Friendly Parks Program” were taken down this month, according to the Environmental Data and Governance Initiative, an investigative journalism nonprofit.

It’s difficult to pinpoint when the documents were pulled, but archived versions of the page reveal it happened between December 6 and December 20, 2017. The National Park Service chose not to disclose the update in the page’s source code, which some agencies elect to do for transparency reasons.

The now-missing documents outlined climate action plans for 92 national parks, or “CFP Member Parks.” As participants in this program, parks aimed to aggressively reduce their greenhouse gas emissions. Joshua Tree National Park in California, for example, intended to reduce its emissions to 50 percent below 2008 levels by 2016. Montana’s Glacier National Park explored the way that vehicle use by visitors contributed to its overall footprint. And Grand Canyon National Park in Arizona vowed to implement a climate adaptation plan to protect its natural and cultural resources.

“The program provides national parks with comprehensive support to address climate change within park boundaries and within surrounding communities,” the National Park Service still says on its website.

It’s uncertain whether the scrubbing of its webpage means the Climate Friendly Parks program is being discontinued. But a link for National Park Service staff—to “learn more about how to become a CFP Member and begin the process today on the My Green Parks website”—is no longer active, as of December 20, 2016. This page has never been archived, so it’s impossible to tell what that resource originally included.

A spokesperson for the National Park Service told Motherboard:

Under Section 508 of the Rehabilitation Act of 1973, the National Park Service, like all federal agencies, has a January 18, 2018, deadline to make electronic information and technology accessible to people with disabilities. As part of that process we are updating PDF documents on NPS.gov that are not yet accessible to all, including climate action plans for nearly 100 parks that were listed on a nps.gov webpage. Those non-compliant PDF documents are temporarily unavailable for download while we work to make them compliant with the revised accessibility standards. In the meantime the PDF documents will be provided by email upon request.

The National Park Service didn’t say when we can expect the documents to return. It’s not immediately clear why the agency didn’t just update the PDFs offline and replace them. But we will continue to follow this story, and will provide updates if there are any.

Additional changes to the program’s webpage affected the introductory paragraph:

The CFP Program features more than 120 member parks from every region across the Service. To read more about what these parks are doing to respond to climate change and move park operations in a more sustainable direction, select the member park below.

Which now requires you to email the agency for access to the PDFs:

The CFP Program features more than 120 member parks from every region across the National Park Service. Many Climate Action Plans have been developed; a list [sic] parks with available documents is below. If you would like to be emailed a copy of any listed park's action plan, please contact the NPS Sustainable Operations Branch: e-mail us.

Another agency that oversees public lands, the Bureau of Land Management, also removed its climate change page, and also told Motherboard that “extensive changes and upgrades” to its website were responsible for the change. The agency, however, has not reinstated the page since it was taken down earlier this year.

Many of the nation’s most popular national parks were members of this program. Part of the “Green Parks Plan,” created on April 22, 2012 under National Park Service director Jonathan Jarvis, it provides actionable ways for parks to respond to, and mitigate, climate change.

The program’s importance is evidenced by its participants, like Joshua Tree National Park and Everglades National Park. Both are extremely threatened by climate change—rising temperatures are already shrinking the range of the iconic Joshua tree. Sea level rise, meanwhile, is disrupting the Everglades’ unique freshwater ecosystems.

Public information that opposes Trump’s environmental policy has steadily disappeared from government websites, starting with the White House. The Interior Department, which oversees the National Park Service, has similarly edited its online climate resources. In the meantime, staff are being ordered to promote fossil fuel development on public lands.