FLAGSTAFF, Ariz. -- U.S. scientists studying the effects of uranium mining around the Grand Canyon say President Donald Trump's budget proposal would halt their work.

The U.S. Geological Survey is leading a multiyear study meant to determine whether the region needs protection from new uranium mining claims well into the future. Right now, no one can stake claims on a 1 million-acre area surrounding the national park until 2032.

The Obama-era ban began in 2012 because of concern over uranium contamination in a river that serves 30 million people. It faced backlash from Republicans, and a portion of it is under review by the U.S. Forest Service.

Trump's 2019 budget proposal would eliminate funding for the USGS-led studies on water resources, dust, plants and animals in favor of other priorities.