Land-use dynamics associated with mangrove deforestation for aquaculture and the subsequent abandonment of ponds.

Abstract

The objective of this study was to evaluate the spatiotemporal dynamics of large area mangrove deforestation, aquaculture pond building, and the subsequent abandonment of ponds in a large delta in Indonesia, namely the Mahakam Delta. So, we developed and applied a novel methodology for exploring the lifespan of aquaculture ponds. Using historical multispectral and radar data, the lifespans of aquaculture ponds across the delta were estimated via a chronological analysis of the landscape into four different states: primary mangroves → deforested mangroves → ponds → abandoned/inactive ponds. Specifically, a combination of sequential classification and rule-based techniques were used to: 1) produce a time series of land cover maps from 1994 to 2015 and 2) quantify lifespans of aquaculture ponds in the delta. Results show that of the 110,000 ha of primary mangrove forests in the delta in 1994, 62% had been deforested by 2015, with a 4.5% annual rate of loss on average. The lifespan of aquaculture ponds in the delta varied between 1 and 22+ years, with most of the ponds having productive lifespans of 10 to 13 years. Ponds with relatively longer lifespans were located near the existing settlements in the delta. This study showed that the productive lifespan of most aquaculture ponds in deforested mangrove lands of Mahakam delta is relatively short, information that should be useful for developing appropriate management plans for the delta or similar coastal mangrove ecosystems. The abandoned ponds can potentially be rehabilitated for shrimp and fish production after applying appropriate restorative treatments or be targeted for mangrove restoration projects.