Mangrove retreat with rising sea-level, Bermuda

• Published in: Estuarine, Coastal and Shelf Science
• Main Author: Ellison, JC
• Format: Article in Journal/Newspaper
• Language: English
• Published: 1993
• Subjects: 300801 Environmental Management and Rehabilitation; Hungry Bay; Low Island
• Online Access: https://eprints.utas.edu.au/2215/; https://eprints.utas.edu.au/2215/1/ECSS1993.pdf; https://doi.org/10.1006/ecss.1993.1042

Low island mangroves keep up with slow sea-level rise by peat accumulation. Holocene stratigraphic records show that they maintain the same pace as sea-level rise at rates up to 9 cm/100 years. Tide gauge records from Bermuda since 1932 show sea-level rise at a rate of 28 cm/100 years. The largest mangrove area (6.26 acres) at Hungry Bay has for the last 2000 years been building peat at a rate of 8.5 to 10.6 cm/ 100 years. Retreat of the seaward edge has caused loss of 2.24 acres of mangroves, commencing in the last few hundred years, with a second dieback between 1900 and 1947, and a third dieback in the last decade. The substrate elevation of the seaward margin of mangroves is below mean sea-level, the normal lower limit for mangroves. Present dieback shows problems of erosion indicating that the Bruun Rule of beach erosion with sea-level rise is also appropriate for mangrove swamps. Stratigraphy shows that before 4000 BP sea-level rose at a rate of 25 cm/ 100 years, from 4000 to 1000 years BP the rate of sea-level rise declined to 6 cm/ 100 years during which time mangroves established, and in the last 1000 years there was an increase to 14.3 cm/ 100 years, during which time the mangroves died back. This study indicates that low island mangroves will experience problems with the rates of sea-level rise predicted for the next 50 years.