Status and changes of mangrove forest in Mekong Delta: Case study in Tra Vinh, Vietnam

Study Number:

32

Author:

P. M. Thu & J. Populus

Abstract:

Because shrimp aquaculture in the Mekong Delta develops rapidly, it has negatively impacted the environment, socio-economics and natural resources. In particular, mangrove forests have been altered by the shrimp aquaculture. The area of mangrove forests in the region has been reduced and this is seen especially in Tra Vinh province. The results obtained from GIS (Geography Information System) and RS (Remote Sensing) show the status of mangrove forests in Tra Vinh province in 1965, 1995 (Northeastern part of Tra Vinh Province) and 2001. In 1965, the area of mangrove forests was 21,221 ha making up 56% of total land-use, while in 2001 it was 12,797 ha making up 37% of total land-use. Also based on GIS analysis, over the 36 years (1965-2001), the total coverage of mangrove forests have decreased by 50% since 1965. However, the speed of mangrove forest destruction in the period from 1965 to 1995 was much less than that in the period from 1995 to 2001. The average annual reduction in mangrove forest coverage in the first period (1965e1995) was 0.2% whereas it was 13.1% in the later period (1995-2001). For the long time, mangrove deforestation has been caused by war, collection of firewood, and clearing for agriculture, and recently, shrimp farming (aquaculture) has significantly contributed rate of mangrove destruction.

Main Results and Conclusions:

• Status of mangrove forest in Tra Vinh: “In 1965 rice paddy was the most use of land in Tra Vinh. The mangrove forests were distributed in Duyen Hai district (Fig. 3 A). Out of the 38,000 ha of Duyen Hai district, the total area of mangrove forests was 21,221 ha (making up 56% of the total of land-use area) in 1965 including 7877 ha in the northeastern part, whereas in 2001 mangrove areas covered only 12,797 ha (making up 37% of the total of land-use area) with 3,122 ha in the northeastern part (Fig. 3 D and Table 3). Some mangrove areas in 2001 were distributed in Tra Cu district but they were lower in density (Fig. 3 C)”(104).
• Shrimp farms (aquaculture) caused low-density forests: “…most areas of mangrove forest, which were low in density, were a mixture between mangrove trees and shrimp farms or canals”(104).
• The general results of the study are as follows: “In the period between 1965 and 2001, reduced area of mangrove forests was 8424 ha (Table 4). The annual rate of the area reduction of the mangrove forests in Tra Vinh was 1.4%, and in the northeast part was 2.5% (Table 4). However, in the northeastern part, the rate of destruction of the mangrove forests in the 1965-1995 period (the rate was 0.2% – Table 4 and Fig. 4 A) was many times lower than that in the 1995-2001 period (the rate was 13.1% – Table 4 and Fig. 4 B). These results demonstrated that in the early period, the shrimp farming in Cau Ngang affected mangrove forest slightly, whereas they significantly increased the destruction of mangrove forests in the later period (Table 4 and Figs. 4 C and 5)”(105-106).
• Often, the rate of planting does not match the rate of deforestation: “The total area of mangrove deforestation between 1965 and 2001 was 14,208 ha while mangrove reforestation was 5784 ha (Table 5 and Fig. 5). The total area of un-changed mangrove was 7013 ha (Table 5 and Fig. 5)”(106).
• Reforestation needs specific biotic and abiotic requirements that are often greatly impaired by shrimp farms: “The large replanting areas of mangrove forest have poor quality in soil nature and are located mainly in shrimp farming areas, which were converted from paddy rice fields having low productivity (Tra Vinh DoF, 1999, 2000, 2001)…Many planting areas have existed in shrimp culture but with low density”(106).
• Most shrimp farming activities in the area were not successful, indicating that in almost all cases natural mangrove habitat is far more productive than any man-made one: “…because of a lack of information about environmental conditions, shrimp culture techniques and financial resources required, shrimp farming failed in some areas or shrimp ponds were used only in the short period (Hong, 1995). After few years, land has been degraded and farmers have continued to cut down mangrove forests and to make new shrimp ponds”(107).
• In conclusion: “This GIS-combined study on historical changes in mangrove distribution in Tra Vinh of the Mekong Delta, Vietnam has demonstrated that over the past 36 years (1965-2001), about 50% of the mangrove forest area was lost, but the reducing annual rate of the period from 1965 to 1995 was lower than that in the period from 1995 to 2000” (107).

Works Cited:

Tra Vinh DoF, 1999. Ba´o ca´o t’^ong k_^et nuoˆi tr_^ong n_am 1999 va` k_^e hoach pha´t tri ’^en nuoˆi tr_^ong thuy’ sa’ n n_am 2000 vu`ng ng ^ap man ven bi ’^en t ’ınh Tra` Vinh (Final report in 1999 and developing plans in 2000 of aquaculture in marsh areas of coastal zone in Tra Vinh province). Department of Fishery, Tra Vinh. 20 pp. unpublished.

Tra Vinh DoF, 2000. Ba´o ca´o t’^ong k_^et nuoˆi tr_^ong thu’ y s ’ an n_am 2000 va` k_^e hoach pha´t tri ’^en n_am 2001, t ’ınh Tra` Vinh (Final report in 2000 and developing plans in 2001 of aquaculture in Tra Vinh province). Department of Fishery, Tra Vinh. 18 pp. unpublished.

Tra Vinh DoF, 2001. Ba´o ca´o t’^ong k^et nuoˆi tr^ong thuy’ sa n vu`ng ng ^ap man ven bi^en tı’nh Tra` Vinh nam 2001 va` phu’o’ng hu’_o’ng nhi ^em vu n_am 2002 (Final report in 2001 and developing plans in 2002 of aquaculture in marsh areas of coastal zone in Tra Vinh province). Department of Fishery, Tra Vinh. 10 pp. unpublished.