grassland

According to the WWF, snow leopards hunt ibex and blue sheep, which stops these animals from overgrazing and helps to preserve grasslands so villagers can feed their livestock.

"You lose a bit each time and the mountain becomes more and more impoverished, more and more grassland like and less and less wet peatland like," he added.

There is not enough evidence to explain what is causing the declines, but one reason could be that there is less grassland and insect food than there used to be because of intensive farming.

A cycle of droughts and floods, the spread of invasive plants that reduced grassland for livestock, and a surge of malaria made matters worse.

About 20 miles north of the Golden Gate Bridge, the Point Reyes Peninsula rises up, a paradise of ocean, dunes, cliffs and grassland that feels delivered from another time and place.