Complex sentence: The Bureau of Land Management is the agency in charge of the Sawtooth Mountains Wilderness, which has a topography of ridges, valleys, and canyons that support a wide array of plant and animal life.
Split into simpler sentences: The Bureau of Land Management is the agency in charge of the Sawtooth Mountains Wilderness. Wilderness topography includes ridges, valleys, and canyons that support a wide array of plant and animal life.