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The spread and cost of saltwater intrusion in the US Mid-Atlantic

Abstract

Saltwater intrusion on coastal farmlands can render productive land unsuitable for agricultural activities. While the visible extent of salt-impacted land provides a useful saltwater intrusion proxy, it is challenging to identify in early stages. Moreover, associated ecological and economic impacts are often underestimated as reduced crop yields in farmlands surrounding salt patches are difficult to quantify. Here we develop a high-resolution (1 m) dataset showing salt patches on farm fringes and quantify the extent of salt-impacted lands across the Delmarva Peninsula, United States. Our method is transferable to other regions across and beyond the mid-Atlantic with similar saltwater intrusion issues, such as Georgia and the Carolinas. Our results show that between 2011 and 2017, visible salt patches almost doubled and 8,096 ha of farmlands converted to marsh—another saltwater intrusion consequence. Field-based electrical conductivity measurements show elevated salinity values hundreds of metres from visible salt patches, indicating the broader extent of at-risk farmlands. More farmland areas were within 200 m of a visible salt patch in 2017 compared to 2011, a rise ranging between 68% in Delaware and 93% in Maryland. On the basis of assumed 100% profit loss in at-risk farmlands within a 200 m buffer around salt patches in 2016–2017, the range of economic losses was estimated between US$39.4 million and US$107.5 million annually, under 100% soy or corn counterfactuals, respectively.

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Fig. 1: Where crops do not grow.
Fig. 2: Changes in visible salt patches between 2011–2013 and 2016–2017.
Fig. 3: Conversion of farmlands to marsh between 2011–2013 and 2016–2017.
Fig. 4: Changes in salt patches and at-risk farmland around these patches between 2011–2013 and 2016–2017.
Fig. 5: Potential loss in profit in US$ from salt patches and at-risk farmlands considering 10 year averages in crop prices.

Data availability

The high-resolution dataset for salt patches and other land covers for 2011–2013 and 2016–2017 are available at https://zenodo.org/record/6685695#.Y9AiVXbMIdU.

Code availability

Sample GEE code is available along with the high-resolution dataset57.

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Acknowledgements

This publication was made possible by the National Science Foundation EPSCoR grant no. 1757353 and the State of Delaware that supported P.M. and V.Y. This work was also supported by the National Aeronautics and Space Administration EPSCoR grant DE-80NSSC20M0220 awarded to P.M., the Delaware Space Grant College and Fellowship Program (NASA grant 80NSSC20M0045) that supported M.W. and the USDA-National Institute for Food and Agriculture (grant 12451226) awarded to J.M., R.E.-N., K.G. and K.T. We acknowledge the support provided to P.M., M.W., J.M., R.E.-N., K.G. and K.T. by the US Environmental Protection Agency (Assistance Agreement no. CB96358101), USDA Natural Resources Conservation Service (Assistance Agreement no. NR193A750007C005) and the National Fish and Wildlife Foundation’s Chesapeake Bay Stewardship Fund (grant 0603.20.071142), as well as the State of Maryland and Harry R. Hughes Center for Agro-Ecology. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.

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P.M. developed the overall study concept and design. K.T. conceived and designed the electrical conductivity analysis. R.E.-N. contributed in certain aspects of the study design. M.W. and P.M. processed, developed and analysed the geospatial data. K.T. and E.N. collected and analysed soil samples. J.M., V.Y. and E.N. contributed to further data analysis. P.M. prepared the first draft of the paper. M.W., K.G., R.E.-N. and K.T. contributed to the writing.

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Correspondence to Pinki Mondal.

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Mondal, P., Walter, M., Miller, J. et al. The spread and cost of saltwater intrusion in the US Mid-Atlantic. Nat Sustain 6, 1352–1362 (2023). https://doi.org/10.1038/s41893-023-01186-6

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