Khnong Phsar, Kampong Speu Province — After a lengthy trek from the nearest village, Lim Sengleang finally reached the peak of Khnong Phsar on a clear day in June. The fresh air and striking views of the surrounding Cardamom Mountains made the hike well worth the effort, said the 26-year-old Phnom Penh resident. But the trail, beautiful as it was, left something to be desired. As Sengleang made his way up the mountain path he passed litter—abandoned bottles, plastic bags, and snack wrappers—and smelly bags full of trash.