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Abstract Integration of natural and cultural resource management is urgently needed to combat the effects of climate change. Scientists must contend with how human-induced climate change and rapid population expansion are fundamentally reworking densely inhabited coastal zones. We propose that a merger of archaeology, environmental science, and land management policy—different yet intertwined domains—is needed to address dramatic losses to biocultural resources that comprise coupled cultural-natural systems. We demonstrate the urgency of such approaches through analyses of coastal archaeological regions within the U.S. Atlantic and Gulf coasts where sea level rise is a primary threat, and we extend our findings globally through an assessment of primary risk factors and forecasts for archaeological sites in the Netherlands, Peru, and Oceania. Results show that across the U.S. Gulf Coast and in Oceania, where little hard infrastructure is in place to protect archaeological sites, hundreds of low-lying coastal sites will be lost under future climate scenarios. In other coasts, like that of the Rhine-Meuse Delta (the Netherlands), risks range from erosion caused by periods of flooding to the degradation of wetland sites caused by extreme droughts. In coastal Peru, population pressures pose the primary risk to archaeological sites through rapid agro-industrial growth, urban expansion, and El Niño climate variability. Across all risks, we propose that management strategies to mitigate losses to biocultural resources must be approached as a restoration process of linked sociocultural and physical environmental systems. 

Abstract Earthquakes present severe hazards for people and economies and can be primary drivers of landscape change yet their impact to river-channel networks remains poorly known. Here we show evidence for an abrupt earthquake-triggered avulsion of the Ganges River at ~2.5 ka leading to relocation of the mainstem channel belt in the Bengal delta. This is recorded in freshly discovered sedimentary archives of an immense relict channel and a paleo-earthquake of sufficient magnitude to cause major liquefaction and generate large, decimeter-scale sand dikes >180 km from the nearest seismogenic source region. Precise luminescence ages of channel sand, channel fill, and breached and partially liquefied floodplain deposits support coeval timing of the avulsion and earthquake. Evidence for reorganization of the river-channel network in the world’s largest delta broadens the risk posed by seismic events in the region and their recognition as geomorphic agents in this and other tectonically active lowlands. The recurrence of comparable earthquake-triggered ground liquefaction and a channel avulsion would be catastrophic for any of the heavily populated, large river basins and deltas along the Himalayan arc (e.g., Indus, Ganges, Brahmaputra, Ayeyarwady). The compounding effects of climate change and human impacts heighten and extend the vulnerability of many lowlands worldwide to such cascading hazards. 

Abstract As large areas of the Mississippi River Delta (MRD) of the USA disappear into the sea, present-day communities and cultural resources are lost. While the land loss may be readily quantified, describing the impact of cultural losses is less straightforward because cultural elements are frequently less tangible and difficult to map, identify, and categorize. The elision of cultural components of landscapes and ecosystems is evident in restoration practices and policies, although numerous scholars have identified the interlinked processes of culture and ecology as critical to rebuilding healthy and resilient environments. We define and measure cultural-ecosystem resilience (CER) in the Mississippi River Delta through analyses of Indigenous oral histories, mound-building practices and settlement patterns, and the persistence and reuse of archaeological sites. CER describes a system containing resilient properties embedded in human-natural settings including river deltas that may manifest in oral cultural traditions, architecture, and the selection of habitable environments. Our interdisciplinary approach demonstrates the role of human-modified landscapes in generating resilience for past and present coastal communities and highlights the importance of consulting records of historic and modern Indigenous traditions in shaping sustainable landscape-management strategies. Results show that archaeological earthen and shell mounds made by Native American Gulf Coast and MRD communities have been persistent features that endured for centuries and are sited in regions of high multicultural value within the dynamic delta. Yet, we document the rapid 20th-century loss of mounds due to coastal erosion, industry, and other human land-use practices. Present-day and future coastal land loss endangers what remains of these keystone features and thus lowers the resilience of modern Mississippi River Delta communities. 

Abstract The principal nature-based solution for offsetting relative sea-level rise in the Ganges-Brahmaputra delta is the unabated delivery, dispersal, and deposition of the rivers’ ~1 billion-tonne annual sediment load. Recent hydrological transport modeling suggests that strengthening monsoon precipitation in the 21st century could increase this sediment delivery 34-60%; yet other studies demonstrate that sediment could decline 15-80% if planned dams and river diversions are fully implemented. We validate these modeled ranges by developing a comprehensive field-based sediment budget that quantifies the supply of Ganges-Brahmaputra river sediment under varying Holocene climate conditions. Our data reveal natural responses in sediment supply comparable to previously modeled results and suggest that increased sediment delivery may be capable of offsetting accelerated sea-level rise. This prospect for a naturally sustained Ganges-Brahmaputra delta presents possibilities beyond the dystopian future often posed for this system, but the implementation of currently proposed dams and diversions would preclude such opportunities. 

ABSTRACT Constraining time is of critical importance to evaluating the rates and relative contributions of processes driving landscape change in sedimentary basins. The geomorphic character of the field setting guides the application of geochronologic or instrumental tools to this problem, because the viability of methods can be highly influenced by geomorphic attributes. For example, sediment yield and the linked potential for organic preservation may govern the usefulness of radiocarbon dating. Similarly, the rate of sediment transport from source to sink may determine the maturity and/or light exposure of mineral grains arriving in the delta and thus the feasibility of luminescence dating. Here, we explore the viability and quirks of dating and instrumental methods that have been applied in the Bengal Basin, and review the records that they have yielded. This immense, dynamic, and spatially variable system hosts the world's most inhabited delta. Outlining a framework for successful chronologic applications is thus of value to managing water and sediment resources for humans, here and in other populated deltas worldwide. Our review covers radiocarbon dating, luminescence dating, archaeological records and historical maps, short‐lived radioisotopes, horizon markers and rod surface elevation tables, geodetic observations, and surface instrumentation. Combined, these tools can be used to reconstruct the history of the Bengal Basin from Late Pleistocene to present day. The growing variety and scope of Bengal Basin geochronology and instrumentation opens doors for research integrating basin processes across spatial and temporal scales. © 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd.