A new technique for rapid assessment of mangrove degradation: a case study of shrimp farm encroachment in Thailand

Abstract

A new technique (Aerial Video Manta Analysis) was developed for the rapid assessment of mangrove degradation due to logging and conversion for shrimp aquaculture. Video recordings were made of mangroves along the Andaman Sea coastline, Thailand, during a 2-day aerial survey (16-17 September 1997) in a small Cessna 206 aircraft at an altitude of 800-1,000 feet and flying speed of 100 knots/h. The video recordings were analysed following a modified Manta-Tow technique, originally developed for coral reef surveys. The percentage cover of good mangrove stands, mangrove areas degraded by logging, and mangrove areas converted into shrimp farms, was estimated for each consecutive 1-min interval of video playing time. The analysis revealed that 9.9±2.2% of the mangroves along the Andaman coastline were severely degraded by logging and 23.3±1.9% had been converted for shrimp farming (a total of 3,255±370 shrimp ponds were counted). The encroachment for shrimp farming was most severe (34%) in Krabi Province, while Phang-nga Province had the most (75%) good mangroves. These results demonstrate that illegal development of new shrimp farms along the Andaman Sea coast has been substantial in recent years. The results obtained by four independent observers using this new method were remarkably close (SD≤25% of mean). The new method allowed cheap, rapid and accurate evaluation of the status of the mangrove resources over a long stretch of coastline within a time-span of a few days. Aerial Video Manta Analysis is a valuable tool to support coastal conservation and management efforts.

Satellite remote sensing of mangrove forests: Recent advances and future opportunities

“…Remote sensing plays a crucial role in the monitoring of mangroves to track deforestation (e.g. Giri et al, 2007;Lee and Yeh, 2009;Manson et al, 2001;Mantri and Mishra, 2006;Paling et al, 2008;Thu and Populus, 2007), the impact of natural disasters such as hurricanes (Doyle et al, 2009;Erftemeijer, 2002) and tsunamis (Giri et al, 2008;Olwig et al, 2007;Sirikulchayanon et al, 2008), reforestation projects (Al Habshi et al, 2007;Beland et al, 2006) and natural coastal dynamics (Fromard et al, 2004).…”

Can Strict Protection Stop the Decline of Mangrove Ecosystems in China? From Rapid Destruction to Rampant Degradation

“…While some efforts have been made to incorporate multiple-level indicators on mangrove ecosystem health [37], there are yet no reports simultaneously assessing the vulnerability at the species, population, community, and ecosystem levels. Most assessments on mangrove degradation have been focused on the decrease in mangrove forest area [22,38,39], whereas the loss of biological and structural diversity as well as ecosystem services is not well documented. Moreover, mangrove managers are satisfied with the apparent end of area loss, and tend to ignore the loss of ecosystem services caused by alterations in the forest biological and structural diversity [25], which could be counter-productive in mangrove conservation [40].…”

The 2004 Tsunami in Aceh and Southern Thailand: Coastal Ecosystem Services, Damages and Resilience

“…the areas most affected by the tsunami. An analysis using aerial video recording by Erftemeijer (2002), however, indicated an increase of (partially uncontrolled, illegal) shrimp farms of up to 25% of mangrove areas. The analysis did not include Ranong Province, but for Phang-nga an area of 5637 ha of shrimp ponds was estimated instead of the previous estimate of 953 ha.…”