High rates of coastal erosion and dune transport are threatening villages and ecosystems in northeast Brazil

Abstract:

Coastal environments support significant populations, but are some of the most sensitive systems to environmental change. Small communities and villages in northeast Brazil rely heavily on ecosystem services such as fishery and forestry to support lives and livelihood, but have already begun to experience the effects of climate change. Increasing global temperatures worldwide are leading to localized changes such as modified tides and wind currents with environmental consequences not yet fully identified and understood. In order to inform local and regional communities manage these problems and adapt to future changes, we urgently need to understand them and be able to predict how these environments might evolve under future climate change scenarios. We present an initial assessment of the issues currently faced by coastal communities in the state of Piauí (PI), Brazil and summarize our findings with ecological and societal risk maps. Areas along the coast are either undergoing coastal erosion or increased landward sand transport, affecting local communities by threatening to either bury or flood farmland, roads, houses, mangroves and damming rivers used to access the sea. We have measured sand migration rates and erosion processes along several linear transects in satellite images from 2009 to 2017. Results show that sand dune fields in Parnaíba, PI are migrating inland at rates that range from 8.8 m/yr to 22.2 m/yr, with an average of 15.6 m/yr. Lower rates are observed near villages and where vegetation has grown over the dunes. Urban maintenance operations such as removing sand from roads is conducted by the local governments and likely also contributes to slower rates close to urban centers. On the other hand, a village in the same area (45 km east of the dune fields) lost an average of 18.9 m/yr of land between 2009 and 2017 due to coastal erosion. According to villagers, these processes are linked to changes in wind speed and tides but confirming this is part of our ongoing research effort. These two examples evidence important processes of coastal morphology change currently happening along vast coastal areas in northeast Brazil. Our findings indicate which areas are at risk and our goal is to highlight the issues, establish the causes, and provide stakeholder input for future urban planning and conservation strategies.