Climate Central: Hike high enough up California's Sierra Nevada and the forest morphs around you. At around 6,000 feet, the dazzling diversity of the lower montane forest, replete with California black oak, ponderosa pine, and incense cedars gives way to more monotonous landscapes of red fir and lodgepole pine. Hike further still and trees eventually disappear altogether, replaced with rocky topographies reminiscent of Mars.
The forestry changes underway threaten to slash the amount of water that flows down the...