The National Park Service is warning that it will close most US national parks if Congress fails to come to an agreement to avoid a government shutdown this weekend, and a popular social media campaign celebrating fat bears will be canceled.

The parks will close as the agency applies lessons learned from previous shutdowns to its closure plans.

“In the event of a lapse in the annual government appropriations, National Park Service sites will be closed. The parks depend on Congress and appropriations to pay staff salaries and keep the parks running. This means that the majority of national parks will be closed completely to public access,” a senior administration official said.