CHANGES IN SPATIAL STRUCTURE OF MANGROVE FOREST ON CA MAU PENINSULA (SOUTH VIETNAM) EVALUATED BY SATELLITE SURVEYS OF 30 YEARS INTERVAL
Son Ton, Dobrynin D.V., Mokievsky V.O. Changes in Spatial Structure of Mangrove Forest on Ca Mau Peninsula (South Vietnam) Evaluated by Satellite Surveys of 30 Years Interval // Ecosystems: ecology and dynamics. 2020. Vol. 4. No. 2. P. 82-95. | Abstract | PDF | Reference |
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- Fidler crabs (Uca) – one of the most common invertebrates of mangroves worldwide (photo by V.O.Mokievsky)
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- Avicennia alba forest; respiratory roots are typical for this genus (photo by V.O.Mokievsky)
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- Mangrove palm Nipa fruticans with fruits (photo by V.O.Mokievsky)
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- Mangrove palm Nipa fruticans under the canopy of Sonneratia alba (photo by V.O.Mokievsky)
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- Inflorescence of Nipa fruticans (photo by V.O.Mokievsky)
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- Collared Kingfisher (Todiramphus chloris) in Avicennia forest (photo by V.O.Mokievsky)
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- Inflorescence of most common mangrove trees of South Vietnam – Rhizophora stylosa (photo by V.O.Mokievsky)
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- Channels in mangrove forest are the main roots of transportation for local peoples (photo by V.O.Mokievsky)
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- Channel in shrimp-mangrove aquaculture with Rhizophora (photo by V.O.Mokievsky)
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- Open sandy shore of South Vietnam (photo by V.O.Mokievsky)
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- Viviparity is a key adaptation of mangroves: propagules of Rhizophora stylosa (photo by V.O.Mokievsky)
The changes in mangrove areas were calculated for thirty-year period (1989-2018) on the Ca Mau peninsula, South Vietnam. Landsat 4 TM and Landsat 8 scenes were used for spatial analysis of mangroves in 1989 and 2018 correspondingly. Spatial resolution of both sensors was 900 m2 on pixel and the size of the analyzed area was 37574.25 ha. In 1989 mangroves covered 22999 ha and in 2018 only 18507 ha. Total loss of mangroves was 4492 ha with mean rate of decline 0.6% per year, which closely corresponds with recent estimated values of degradation of mangroves in SE Asia in general. However, simple comparison of total areas for 2 years does not reflect the spatial transformation: the disappearance of the old forests in one area and its appearance on the newly accumulated tidal flats. Comparison of the spatial mosaics for these 2 years evaluates greater figures of changes. Intact area comprised 10557 ha or less than 50% of mangroves in 1989. In the area of 12442 ha the mangroves disappeared completely, and then recovered on the area of 7950 ha. Along the decrease of mangrove vegetation in the studied area the rate of fragmentation increased drastically. The relative proportion of small patches (1-100 ha) increased about tenfold – from 4 to 34% of total mangrove coverage. The study showed that decrease of total area covered by mangroves, as a difference of total coverage between comparing years, does not provide sufficient measures for mangrove transformation rates. It does not include spatial and structural changes of mangrove forests. The area of intact mangroves used to be much smaller than total area at given year, and the structural changes affect the age structure of mangrove forests.
Keywords: mangroves, dynamics, Mekong Delta, Vietnam, Ka Mau.
DOI: 10.24411/2542-2006-2020-10061