By noon on Thursday, Davis Erin Anderson had copied the addresses of a few dozen websites and online PDFs that listed signs of climate change by state and region.

In a book-lined room on the third floor of the New York Academy of Medicine in Manhattan, Ms. Anderson was hunched over a laptop, working her way through a list of states.

All of the material had been posted by federal agencies, and Ms. Anderson was sending it off to an archive so that it would not disappear when the new presidential administration took office in January.

“I’m up to Maryland,” she said. “My goal is to get through them all today.”

With the arrival of any new president, vast troves of information on government websites are at risk of vanishing within days. The fragility of digital federal records, reports and research is astounding.