Progress in coupling models of human and coastal landscape change

4 Humans are increasingly altering the Earth’s surface, and affecting processes that shape and 5 reshape landscapes. In many cases, humans are reacting to landscape-change processes that 6 represent natural hazards. Thus, the landscape is reacting to humans who are reacting to the 7 landscape. When the timescales for landscape change are comparable to those of human 8 dynamics, human and ‘natural’ components of developed environments are dynamically 9 coupled—necessitating coupling models of human and physical/biological processes to study 10 either environmental change or human responses. Here we focus on a case study coupling 11 models of coastal economics and physical coastline change. In this modeling, coastline change 12 results from patterns of wave-driven sediment transport and sea-level rise, and shoreline 13 stabilization decisions are based on the benefits of wide beaches (capitalized into property 14 values) balanced against the costs of stabilization. This interdisciplinary modeling highlights 15 points that may apply to other coupled human/natural systems. First, climate change, by 16 accelerating the rates of landscape change, tends to strengthen the coupling with human 17 dynamics. In our case study, both increasing sea-level-rise rates and changing storm patterns 18 tend to increase shoreline change rates, which can induce more vigorous shoreline stabilization 19 efforts. However, property values can fall dramatically as erosion rates and stabilization costs 20 rise, which can also lead to the abandonment of expensive stabilization methods as shoreline 21 change rates increase. Second, socio-economic change can also strengthen the human/landscape 22 coupling. Changing costs of shoreline stabilization can alter stabilization decisions, which in turn 23 alters patterns of coastline change. The coupled modeling illuminates the long-range effects of 24 localized shoreline stabilization efforts; communities arrayed along a coastline are unwittingly 25 affecting each other’s erosion rates, and therefore each other’s economies. Our coupled modeling 26 experiments show that spatial distributions of property values and erosion rates can jointly affect 27 economic outcomes, resource allocation between communities, and patterns of shoreline change. 28 These findings raise questions about coastal management strategies, and efficient and equitable 29 allocation of scarce resources among coastal communities. 30 31