|Abstract: Approximately one fifth of the world's population lives in watersheds originating on the Tibetan Plateau. The grasslands of the plateau are becoming degraded, with one corrective action being the poisoning of a native mammal, the plateau pika (Ochotona curzoniae). This poisoning has occurred for five decades, is massive, and has not improved rangelands. Rather than being a pest, pikas are a keystone species for biodiversity and ecosystem engineers. The burrows of pikas may loosen soil, increase water infiltration rates and decrease runoff. In poisoned areas these processes may be reversed. We propose to conduct ecohydrology experiments in areas with pikas and areas where poisoning has occurred to test the hypothesis: pikas inhibit runoff and reduce the potential for erosion. We believe this analysis will serve as a wake-up call to Chinese policy-makers, so that poisoning of pikas will cease, with concomitant benefits to biodiversity and the sustainability of these grasslands.