1. Climate change in the Mekong region, a potential catalyst for socio-ecological imbalances

The Mekong region contains the world’s 12th longest river, which flows from the Tibetan Plateau through China, Myanmar, Thailand, Laos, and through the rich Mekong Deltas in Cambodia and Viet Nam. Altogether, it drains a basin area of 810,000 km2 and is home to over 65 million people. The basin plays a crucial role in the livelihoods of millions of people from six countries: Cambodia, China, Laos, Myanmar, Thailand, and Viet Nam. After a troubled history, the region has embraced modern diplomacy to tackle the various interests and potential conflicts associated with using and amending transboundary resources such as water and fish [ Kittikhoun & Staubli, 2018 ]. While resource use and exploitation have contributed to socio-economic progress, the changes have also brought environmental disturbances, and various risks to the life and livelihoods of millions of people. Until today, people in the region have experienced various impacts from environmental changes, which include — but are not limited to – hydrological fluctuation, degradation of water and related resources, pollution from fast developing cities, deforestation, and others [ Stibig et al., 2014; Simpson, 2007; Hirsch, 2016; and Chapters 7 and 9 of this report for the case of the Vietnamese Mekong Delta ].

Climate change adds to these ongoing environmental problems by increasing the region’s fragility. Various studies analyse possible changes in the region linked to climate change scenarios. There are possibilities of higher temperature, increased precipitation, increased melting of glaciers in the Upper Mekong [ Eastham et al., 2008 ], followed by a temporary increase in runoff, thus changing the seasonal discharge (ibid, Hoang et al., 2016; Chapter 5 of this report for the analysis of the impact of climate change on the hydro-energy supply). Another projection of climate change influence concerns the decline of groundwater recharge in short-medium-, and long-terms [ Shrestha et al., 2016 ]. The most likely impacts of climate change in the region are linked to temperature change (e.g. more severe drought), unexpected climatic events and hydrological alternation. In fact, a high confidence conclusion from the Intergovernmental Panel on climate change (IPCC) states that global warming is likely to reach 1.5°C between 2030 and 2052 if human activities associated with the industrial regime continue to increase at the current rate [ IPCC, 2018 ]. Chapter 1 and 7 of this report confirm these findings in the case of Viet Nam.

One meter of sea level rise was supposed to cause the displacement of 7 million inhabitants and flood the homes of more than 14.2 million people in the Vietnamese Mekong Delta [ ADB, 2013 ] even before the elevation of the Delta was recently re-evaluated [ Minderhoud, 2020 ]. This is even more critical in a country like Viet Nam, which is ranked fifth out of 233 countries in terms of direct extreme weather risk (physical climate impact) (see Part 1 of this report for further details on this matter). The changes will either worsen or improve flooding and drought in the region. Negatively, there could be worse flooding events in the rainy season and droughts in the dry season in the basin, with increasing water shortage, and deeper and more uncertain salinization in the downstream Mekong Delta. While changes in hydrological system have

both positive and negative impacts, the risk is getting higher with uncertain weather and extreme events. Further impacts on livelihoods in the basin are under research and projection, e.g. the impact of climate change on agriculture and food security. So far, it is still unclear whether climate change could affect regional agriculture [ Eastham et al., 2008 ], or as Mainuddin et al. (2011) conclude, that food security in terms of total production appears unlikely to be affected in the future by the threat from global climate change (see Chapter 4 of this report for another approach to food security and climate change in Viet Nam). Yet, extreme whether events could hamper production and farmers’ livelihoods. Recent research at a smaller scale asserts that climate change could depress rice yields in the Vietnamese Mekong River Delta (Kontgis et al., 2019; see also Chapter 4 of this report for the case of rice in the Delta).

Climate change is one of various environmental issues that exacerbate already existing socio-economic impacts. Indeed, social stressors, including marginalization, lack of access and rights to natural resources, and poverty are interlinked with environmental changes. Due to socio-economic differentiation, the risks of climate change for natural and human systems vary between nations and between groups of people. It depends on the magnitude and rate of warming, geographic location, levels of development and vulnerability, and on the choices and implementation of adaptation and mitigation options [ IPCC, 2018 ]. While each inhabitant is facing issues [ O’Brien 2012, O’Brien and Sygna, 2013 ], the decisions made in a growing economy have put more people, assets, and resources in the path of encroaching climate change [ McElwee, 2017 ]. In the end, climate change is not an external threat, but a problem both of development and for development. Adaptation is thus about adapting with climate change (adopted from Pelling, 2011). The current complex situation points to the fact that business-as-usual is no longer appropriate. And integrating adaptation into ‘development-as-usual’ paradigms runs the risk of reproducing the system that creates vulnerabilities in the first place [ Eriksen et al. 2014 ].

As stated above, climate change, as currently understood by the scientific world and general public, will likely affect socio-economic development, the safety of millions, and ecosystem dynamics, and has thus obtained special attention. Especially, uncertainty is a threat from climate change which adds to current water resource management, and thus perturbs any agreement for resource sharing [ Bernstein et al., 2008 ]. In the Mekong basin, it adds to the complexity of transboundary water diplomacy, which has been based on the use of diplomatic instruments to solve or mitigate existing or emerging disagreements and conflicts over shared water resources, for the sake of cooperation, regional stability, and peace [ Schmeier, 2018; Kittikhoun & Staubli, 2018, Klimes et al., 2019; Keskinen et al., 2021 ]. Munia et al. (2020) state that any change in upstream basins, either due to changing climate or changes in water use, directly impact on downstream water availability — a property that makes transboundary water management challenging.

Transboundary governance of resources has never been an easy task. While livelihoods along the Mekong river and its tributaries are connected, through the flow of water and attached resources like sediment and fishes, the development and exploitation of those resources are confined within localities, mostly within national boundary. Often, the transboundary aspect of the national development of