Over six dozen groups on Friday demanded President Donald Trump rescind a June executive order directing federal agencies to cut a third of their advisory committees, saying the order threatens widespread harm.

"The value of our government's federal advisory committee infrastructure cannot be overstated," the groups wrote in their letter (pdf) to Trump.

When the president first issued the order, it was met with sharp criticism by experts who called it "an all-out assault on science" and an attack on independent advice. Monday marked the deadline for each agency to make the cuts.

The Hill reported this week on the first two known casualties: the Marine Protected Areas Federal Advisory Committee run by the National Oceanic and Atmospheric Administration (NOAA) and the Interior Department's Invasive Species Advisory Committee.

The signers of the new letter—77 groups and institutions representing diverse issues including the American Public Health Association, CREW, Georgetown University, the National LGBTQ Task Force, and the Union of Concerned Scientists—wrote that the administration's stated cost-savings rationale doesn't hold water.

[A]dvisory committees provide substantial value to agencies for costs far below those of hiring additional staff or contractors to perform the duties they fulfill... Gathering premier experts who volunteer their time to deliberate on pressing matters is a bargain for taxpayers. Further, there is no evidence to support that cutting advisory committees will result in fewer agency costs. To the contrary, a GAO report examined the costs before and after President Clinton's 1993 executive order that cut committees and found that while the number of advisory committees declined during the four years after the order, the costs increased by four percent.

The Trump-imposed cap of 350 committees—governmental bodies that debate issues "from the best way to minimize exposure to lead from drinking water to understanding how best to collect information as a part of the U.S. census"—also has no sound basis and does nothing to ensure science-based decisions, the letter stated.

The Department of Health and Human Services, for example, is now forced "to choose between a range of active public health needs, from infant mortality to sickle cell disease."

The Environmental Protection Agency is in a pickle as well, stuck with choices such as whether to cut "a committee studying how best to protect children's health or one that focuses on environmental justice issues," wrote the groups. They added:

The process by which advisory committees operate provides avenues for all stakeholders to give input on agency actions, as all advisory committees hold open meetings with public comment opportunities. The federal advisory committee process is an important and unmatched venue for transparent deliberations on federal matters that gives members of the public the opportunity to observe and hold agencies accountable.

Committee removals, wrote the groups, "will undoubtedly result in a net loss of independent expert capacity and institutional knowledge and leave important work unfinished or underdeveloped."

Genna Reed, lead science and policy analyst for the Center for Science and Democracy at the Union of Concerned Scientists, called the executive order "the latest example of a pattern across this administration of excluding science from government to the detriment of public health," and explained how it will prove to be a loss for all.

"It's not just the scientists offering up their time to serve the public who will be hurt by these cuts—it's communities across the country who deserve to benefit from policy based on evidence," Reed said in a press statement. "The president needs to revoke this thoughtless executive order."