Sierra Club endorsement raps Reagan on ecology

The Sierra Club, breaking with a tradition of nonpartisanship in a counterattack against Reagan administration environmental policies, has endorsed Rep. Sidney R. Yates (D) of Illinois for reelection.

Mr. Yates ''has not hesitated to stand up to (Interior Secretary) James Watt and the other extremists President Reagan has let loose upon the land,'' said Sierra Club president Joseph Fontaine.

Mr. Fontaine said that the environmental group has nothing against Yates's opponent in the March 16 primary, Chicago assistant city attorney John B. McCauley, but that he would not have as much influence as the incumbent.