BILLINGS, Mont. — President Donald Trump’s administration is trying to merge the government’s wildland firefighting efforts into a single agency, a move some former federal officials warn could increase the risk of catastrophic blazes and ultimately cost billions of dollars. …Budget documents do not disclose how much the change could cost or save. …The Trump administration in its first months temporarily cut off money for wildfire mitigation work and sharply reduced the ranks of federal government firefighters through layoffs and retirement. …But organizations representing firefighters and former Forest Service officials say it would be costly to restructure firefighting efforts and cause major disruptions in the midst of fire season. …“You will not suppress your way to success in dealing with catastrophic fires. ….” said Steve Ellis, the chairman of the forest service retirees group and a former wildfire incident commander.