AP Photo/Mead Gruver

Tom Wiersema, who has been trout fishing on the upper North Platte River in Wyoming since the 1970s, stands by his drift boat near Encampment, Wyoming. Low water caused him to stop fishing by boat on a long stretch of the river earlier than usual this year. The upper North Platte is one of several renowned trout streams affected by climate change in the western U.S.