Dynamic Asia: Coupling of climate, tectonics, rivers, and people defines risk and opportunity for the world’s largest human populations

Abstract:

Coupling between the Himalayan-Tibetan uplift and intense Asian monsoon yields tremendous regional runoff and sediment supply. This vigorous mass-transfer system sustains 7 of the world’s 10 largest riverine sediment loads, which in turn have constructed vast, fertile fluvial-deltaic lowlands. These environments across south and east Asia host about 1/3 of all people on Earth. Such large and dense populations have flourished amidst the region’s generally abundant water supplies, fisheries, and agricultural production. Yet the same environmental attributes that are so rich in resources also define a uniquely dynamic region, where rates of change are rapid and punctuated by frequent, intense events. Indeed, 8 of the world’s 10 deadliest natural disasters have occurred in this region, involving a combination of earthquakes, tropical cyclones, river floods, and tsunamis. Other stresses that regularly impact the region include periods of monsoon collapse and drought, widespread arsenic contamination of groundwater, relative sea-level rise and coastal inundation, and groundwater salinization.

Thus the communities of this region persistently face the challenge of balancing the carrying capacity of a resource-rich environment with its associated hazards and challenges. One important concept that has become increasingly more apparent is the connection within watersheds that transmits local effects both upstream and downstream within the system. Here we emphasize two additional points that we believe are essential in developing plausible strategies for sustaining health, resilience, and stability of the region. First, problems related to the natural environment are closely coupled with human activities and our concurrent responses to environmental change. Thus resulting issues are complex and multifaceted in ways that require natural scientists to better engage with researchers in the humanities and social sciences. Second, despite similar risks affecting many millions of square kilometers, the impacts of, and solutions to, such risk necessarily play out at much smaller scales closer to tens to a few hundred kilometers. This scaling includes both the natural and human landscape, underscoring the need to account for local variation in our scientific investigations.