The Intergovernmental Panel on Climate Change (IPCC Fifth Assessment Report (AR5)) noted global mean sea level rose significantly since the Industrial Revolution and has been accelerating1. The inhabited Tangier Islands, the focus of the present study, lie within a “hot spot” of RSLR (relative sea level rise) in Chesapeake Bay waters bordering the mid-Atlantic (Virginia, USA) significantly higher than the global mean SLR (sea level rise)2,3,4,5,6,7. The Islands, comprised mostly of estuarine wetlands with a number of sandy upland ridges, were settled in the 1700s by European colonists8 and have been inhabited since, with 727 people living on the island as of 2013. Using geo-referenced maps dating from 1850–2013, we show the Islands have lost the majority of their landmass since the first accurate map was made in 1850; by 2013, only 33.25% of the 1850 landmass remained. Modeling using ARCGIS and the USGS Digital Shoreline Analysis System showed that, under a mid-range RSLR scenario, most of the remaining landmass of the Islands will be lost within 100 years and the Islands will likely have to be abandoned in approximately 50 years.

Analysis in the AR5 report lists the following: accelerating rates of global mean SLR: 1.7 mm yr−1 (1901–2010), 2.0 mm yr−1 (1971–2010) and 3.2 mm yr−1 (1993–2010) and predicts 60–100 cm SLR by 21001. Locally, RSLR (relative sea level rise) has been higher, due to a SLR “hot spot” along the Atlantic Coast of North America2, part of a region in the North Atlantic above global mean SLR2,3. This “hot spot” extends from Cape Hatteras, NC to Boston, MA and rose 3.80 ± 1.06 mm yr−1 (1970–2009). The Southern Chesapeake Bay region, within this “hot spot,” had a higher rate of SLR (4.40 ± 0.086 mm yr−1 from 1955–2007), due to land subsidence (2.101 mm yr−1) due to glacial rebound caused by the Laurentide ice sheet melting4,5, groundwater extraction, as well as after effects of a meteor impact near Cape Charles, VA approximately 35.5 million years ago6, which is still causing local land subsidence7. Glacial rebound is causing a significant portion of local land subsidence, with groundwater pumping being the other major factor. Aquifer-system compaction is causing more than half of local land subsidence, especially near population and agricultural centers. This compaction can account for more than 50% of observed land subsidence rates in the region and even more so near regions where extensive groundwater pumping is occurring, such as near the cities of West Point, Franklin and Norfolk, Virginia8,9. Due to the isolation of Tangier Island from major population and agricultural centers responsible for extensive groundwater pumping, groundwater pumping related subsidence at Tangier Island may be less than 50% of total subsidence reported locally, but it is likely significant.

Chesapeake Bay is the largest tidal estuary in USA. It is located along the East Coast of the USA in the mid-Atlantic region, with the northern portion (approximately half) lying within the State of Maryland’s border and the southern portion lying in the State of Virginia’s border. At initial European settlement (1600s), the Chesapeake Bay had hundreds of islands (1-800 HA in size). Many islands (>500) have been lost to SLR and erosion since the 1600s and losses continue10. Few islands were ever inhabited (~39), as most lacked sufficient uplands for habitation. Declines in upland areas resulted in abandonment of some of the largest islands in the early 1900s, including Bloodworth11, Holland12 and Uppards Island10. Uppards is one of the Tangier Islands, the focus of the present study.

The Tangier Islands are a complex of what are now several islands, once connected, located in Virginia waters of Chesapeake Bay (Fig. 1) near the border between Virginia and Maryland approximately 151 km southeast of Washington DC. The main remaining Tangier Islands are, from north to south, Goose, Uppards, Port Isobel and Tangier Island. The Tangier Islands lie 22 km east of mainland Virginia and 16.2 km west from the Eastern Shore, a peninsula that partially encloses Chesapeake Bay. The West side of the Bay has deeper waters than those East of the Islands. Due to the longer fetch, wave action along western shores of the Islands is more powerful. Large SAV (seagrass) beds (μ = 296 HA from 2003–1313) lie immediately east of the Islands, which protect the SAV from the western fetch. A 1.74-km long rock revetment was constructed along the majority of western shore of Tangier Island in 1989 at a cost of 10.614 million (inflation-adjusted 2014 USD). It has successfully protected a small airport (48.98 HA, 1.5 m above PMSL (Present Mean Sea Level) and nearby Town of Tangier (33.59 HA, 1.46 m above PMSL). The Town is on three upland sand ridges ranging in length from 518–1859 m and up to 396 m wide14. It is primarily an isolated fishing community, with a significant portion (13%, the highest total for any town in Chesapeake Bay) of the most valuable fishery in the Bay, blue crabs, Callinectes sapidus. This fishery (~30 million USD yr−1 ex-vessel revenue in Virginia)15 provides the majority of the income for Tangier fishermen. The Town relies on artesian wells drilled approximately 300 m deep into an Eocene era aquifer beneath the Bay and the average amount of water pumped has been 380 m3 day−1 (Mills et al. 2005), which, when compared to the pumping near large population centers in southeast Virginia that have caused local subsidence near the pumping areas the amount of water pumping by the citizens of the Town of Tangier appears to be insignificant with respect to local subsidence. The construction of a navigation channel between Tangier and Uppards Islands in 1967 may have accelerated local erosion along Uppards due to boat wakes. Placement of dredged material in several landward cells (<10 HA) in the mid-to-late 1900s increased elevation in a few areas, particularly on Port Isobel. Along the eastern shore of Port Isobel, six stone breakwaters were placed in the 2000s for shoreline protection.

Figure 1 Location and configuration of the Tangier Islands, in Virginia waters of Chesapeake Bay, USA. Map created using ESRI ArcGIS, ArcMap 10.1. Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo and the GIS User Community. For more information on this map, including the terms of use, visit: http://goto.arcgisonline.com/maps/World_Imagery. Full size image

Wetlands have significant value, providing ecological services estimated as high as $ 10,000 USD ha−1 yr−1 (in 2014 USD)16. The SAV beds found locally consist of two species, eelgrass (Zostera marina) and widgeongrass (Ruppia maritima). SAV has both ecological and economic value, providing a wide suite of ecosystem services including erosion control, coastal protection, water quality improvement, nursery habitat for fish and shellfish, particularly blue crabs (MEPS Ralph) and carbon sequestration17. SAV has an overall value estimated at over $ 20,000 USD HA−1 yr−1 18. The islands provide nesting habitat for waterbirds in Chesapeake Bay, requiring the absence of large terrestrial predators. Bird use has declined as the islands have eroded and lost elevation19.

A prior study focused on Uppards Island predicted that Uppards would be completely lost by 210020. In this study, the effects of sea level rise (assumed to continue at present, at the time of the study, rates, which the authors noted was likely conservative), wave fetch, wind speed and direction were examined and the resultant erosion rate was estimated for the Western and Eastern shore of Uppands, Port Isobel and Tangier Island by selecting 10 points along the western and eastern shoreline of all the islands. The study then projected the fate of the islands in 2100. At this time, based on erosion rates extrapolated to 2100, the study authors predicted that Uppards Island would be completely eroded, with relatively small changes occurring to Port Isobel and Tangier Island. No predictions were made as to the future habitability of the Town of Tangier at 2100 or the types of habitat (upland or wetland) that might be present, though study authors did note that interior water had increased over time and that present upland ridges may need to be raised in the future. Our hypotheses are that Uppards and Goose Island will be lost before 2100 and that, without human intervention, the Town of Tangier will have to be abandoned prior to 2100.