In the face of the dire predicted consequences of planned development on the Mekong River basin, Cambodian Prime Minister Hun Sen and the leaders of Vietnam, Laos and Thailand jointly agreed to consider comprehensive scientific findings in their future decision-making on Thursday.

“Climate change, natural disasters, over-population, unsustainable industrialisation, intensive agriculture, irrigation, hydropower, and other development activities in the basin all constitute major challenges to the Mekong River Basin,” reads the Siem Reap declaration, adopted by the prime ministers of the four MRC member countries at the close of the third Mekong River Commission (MRC) Summit. The document further identifies “the loss of environmental assets, wetlands and natural fisheries, deforestation, floods and droughts and risks to biodiversity and people’s livelihoods and assets”.

“All these are compounded by the effects of climate change, as well as past and ongoing developments in all water and related sectors,” it says.

Importantly, the declaration notes the MRC’s Council Study, a 3,600-page scientific assessment on the impacts of development – in particular hydropower – on the lower Mekong Basin.

The key findings of that study are precipitous predicted declines in fisheries, biodiversity, loss of economic growth, increase in poverty across the region and a monumental decline in sedimentation – the process by which important nutrients for fish and agriculture are carried by a river downstream – all of which must now be considered “as a reference for planning and implementation of national plans and projects”.

What’s more, the declaration also acknowledges the development on Mekong tributary rivers as requiring regional oversight.

“The increasing development in the mainstream and tributaries highlight[s] the increasing need for the sustainability and coordinated operational management of tributary and mainstream water resources development projects,” it says.

The declaration was pre-empted by statements from each of the four country’s prime ministers, as well as by high-level delegates from “dialogue partners” Myanmar and China.

Worth noting, said Brian Eyler of the Stimson Center think tank, was the resounding endorsement of the MRC’s reforms under CEO Pham Tuan Phan.

“What was once described as an institution adrift has been transformed into an effective, localized transboundary river organization,” he wrote in an email.

However, he cautioned that it’s up to governments to follow through on using the Council Study for planning and decision-making.

An English translation of Hun Sen’s remarks said members’ “common mandate and goal are to ensure the benefits provided by the Mekong . . . would be sustained for future generations”.

However, the statement otherwise failed to directly mention the Council Study and its dire predictions for the Kingdom’s future, including an up to 40 percent drop in fish biomass by 2040 and billions in lost GDP growth.

Eyler noted that the Council Study’s predictions for the Kingdom are very conservative and “magnitudes lower than most peer-reviewed studies of similar impacts”.

Transcripts of Laos’s and Thailand’s prime ministers’ statements were not immediately available, but according to Eyler, Laos Prime Minister Thongloun Sisoulith appeared set to go ahead with his country’s planned dam projects, which he maintained were properly approved. Eyler said Thai Prime Minister Prayuth Chan-ocha, meanwhile, hinted at an ambition for “for Thailand’s government agencies, academic institutions, and civil society organisations to rise up as the region’s sustainability leader”.

But it was Vietnamese Prime Minister Nguyen Xuan Phuc who most forcefully raised the alarm in his remarks.

“Mekong water resources have been degraded both in quantity and quality, the amounts of alluvium and nutrients are decreasing and the ecosystem and environment are seriously deteriorated,” Nguyen said. “All these negative signs are more permanent and severe in the lower Mekong basin, especially the Mekong delta of Vietnam in particular [where] the protracted drought, saline intrusion, the erosion of coastlines and riverbanks and land subsidence, [and] the livelihoods of over 20 million people are under threat.”

He went on to call for “concrete and timely action” to ensure the basin continues to be the “rice bowl and fishing ground in the region”, as it has been for centuries.

However, Vietnam aside, conservationists such as Maureen Harris of International Rivers said the declaration and statements “don’t go far enough given the scale of the threats to the basin’s ecosystems and people”.

“However, what is now critical is that the findings and recommendations are taken up by member governments in a meaningful way and used [to] inform policy and practice,” she wrote in an email, noting that renewable alternatives to hydropower must be considered as they are explicitly recommended in the Council Study.

She also called for a moratorium on further hydropower construction “until a regional study of renewable energy technologies . . . is completed,” she said.

Cambodia National Mekong Committee Secretary-General Te Navuth said in an interview on Thursday that while the Kingdom’s position on hydropower hasn’t shifted, the declaration signals a more cautious approach, and an opening to considering alternatives.

“I think the solar and wind power are still not popular in our region, but if they are cheaper then maybe they are an alternative . . . if they can meet the demand,” he said.

Meanwhile, uncertainty remains over China’s ambitions in regional water management and the future of the MRC in light of the establishment of Beijing’s Lancang-Mekong Cooperation Mechanism in 2015, followed by the creation of a water management centre last year. China’s statement at the summit, delivered by Water Resources Minister E Jingping, stated a “willingness” to work with the MRC, and that the LMC “will not replace” but rather “coordinate” with the body.

Harris said China’s involvement in the summit and proposed collaboration between the LMC and MRC “will help address the current lack of accountability for the impacts of existing hydropower projects, including downstream impacts of Lancang dams on riparian communities in the Lower Mekong”.

“The cooperation should include establishing stronger water governance procedures for the basin that include China,” she said.