Amid the torrent of executive orders signed by President Trump were directives that affect the language on government web pages and the public’s access to government data touching on climate change, the environment, energy and public health.

In the past two months, hundreds of terabytes of digital resources analyzing data have been taken off government websites, and more are feared to be at risk of deletion. While in many cases the underlying data still exists, the tools that make it possible for the public and researchers to use that data have been removed.

But now, hundreds of volunteers are working to collect and download as much government data as possible and to recreate the digital tools that allow the public to access that information.

So far, volunteers working on a project called Public Environmental Data Partners have retrieved more than 100 data sets that were removed from government sites, and they have a growing list of 300 more they hope to preserve.

It echoes efforts that began in 2017, during Mr. Trump’s first term, when volunteers downloaded as much climate, environmental, energy and public health data as possible because they feared its fate under a president who has called climate change a hoax.

Little federal information disappeared then. But this time is different. And so, too, is the response.