Can Unleveed Agricultural Fields in Deltas Keep Pace With Sea-Level Rise?

Effective coastal management requires a fundamental understanding of the impacts of anthropogenic activities on sediment dynamics, yet it is challenging to isolate individual impacts in heavily altered regions. The Ayeyarwady Delta, Myanmar has been extensively deforested for agriculture but has few levees/polders. In this study, the relative resilience to subsidence was compared between a 45-year-old agricultural field and a nearby mangrove-forest preserve. At both sites, water velocity and turbidity were measured in tidal channels, topography was mapped, and sediment cores were collected during 2018-2019. There was net sediment import at both sites due to sediment trapping by vegetation. Relative elevations were equivalent, suggesting that the field has aggraded at rates similar to the forest (0.7 cm/year). Unleveed fields may be less vulnerable to subsidence than leveed fields. However, uncertainties remain and the decision to replace mangroves with agricultural fields should weigh all the benefits provided by each environment.

Automated summary

Effective coastal management requires a fundamental understanding of the impacts of anthropogenic activities on sediment dynamics. In this study, the relative resilience to subsidence was compared between an agricultural field and a nearby mangrove-forest preserve in the Ayeyarwady Delta, Myanmar. The results showed that both sites had net sediment import due to vegetation trapping, and the relative elevations were equivalent, suggesting similar aggradation rates. Unleveed fields may be less vulnerable to subsidence than leveed fields, but the decision to replace mangroves with agricultural fields should consider all the benefits provided by each environment.