Cheay Areng was a 108-megawatt hydroelectric scheme on the Areng river in the Cardamom Mountains of Koh Kong province, and by the standards of the Mekong basin it was not large - a fraction of the output of the big mainstream dams, in a country whose electricity demand was climbing fast enough to make almost any project look justifiable. Foreign companies had circled it since 2006, and it passed from hand to hand the way marginal infrastructure often does. China Guodian Corporation intended to build it at one point. In February 2014, Sinohydro Resources was granted approval for six months of drilling, geological mapping and prospecting in the valley. Villagers pointed out that the power would flow principally toward the grid and beyond it, while the losses would be entirely local and entirely theirs.

The march was organised by But Buntenh, and the monks who joined him were young. Koem Bunloerum was thirty, Ngim Saosam Khan thirty-three; both had come from Phnom Penh to a valley most Cambodians could not find on a map. What they offered was not a legal argument but a moral one, expressed in the vocabulary a Cambodian village actually shares. Wrapping a tree in monastic cloth places it, unmistakably, on the sacred side of a line. "Trees bring rain," Koem Bunloerum said. "With no trees, I am afraid that Cambodia will become like the Sahara." It was a hard argument to answer with an environmental impact assessment, and it travelled: the image of saffron in the forest reached audiences that a technical objection never would.

The resistance was not imported. Roughly fifteen hundred people faced relocation from the valley, most of them Chong and Sui - Indigenous communities whose families had lived along this river for centuries - and they organised motorcade marches, petitions and sustained civil disobedience, joined by lawyers, scientists and a coalition of NGOs. Mother Nature Cambodia, founded in 2013 by the Spanish activist Alejandro Gonzalez-Davidson, made Areng its first major campaign and its defining one. The state's response was to remove him: expelled from Cambodia in 2015 and sentenced in absentia to twenty months, a conviction eventually overturned on acquittal in 2019. The organisation lost its official NGO status in 2017 and its members have faced prosecution repeatedly since, including ten convicted in July 2024. In 2023 it was named a Right Livelihood laureate.

In 2017 Prime Minister Hun Sen shelved the project, citing the strength of local opposition - a rare outcome in a country where large infrastructure rarely loses. What the valley kept is considerable: intact forest holding thirty-one endangered animal species, and a stretch of river supporting what has been described as the second-largest wild population of Siamese crocodiles anywhere, a species that had been written off across most of its historical range. What the country got instead was a coal-fired power station in Preah Sihanouk, announced as compensation for the lost generating capacity. Nobody involved pretended that was an environmental victory. And the word used was shelved. Dam proposals in this region have a way of resurfacing when the political weather changes, and the people of the Areng know it better than anyone.