Mangrove forests of Cambodia: Recent changes and future threats

Study Number

110

Author

Bijeesh Kozhikkodan Veettil, Ngo Xuan Quang

Abstract

Mangrove forests around the world are critical agents for coastal area protection, ecosystem services and socioeconomic functions. Cambodia is rich is natural resources such as mangrove forests. There are many discrepancies in the estimated area of mangrove forests by different agencies over a few decades in Cambodia. In this study, decadal changes in mangrove forests along the Cambodian coastline were analysed using satellite data (Landsat series). Overall loss of mangrove forests between 1989 and 2017 has been estimated as 42% (1415 ha/year) in the four coastal provinces of Cambodia (Koh Kong, Kampot, Preah Sihanoukville, and Kep). Individual losses of mangrove areas in Koh Kong, Kampot, Sihanoukville and Kep during the study period were 39%, 45%, 52% and 34%, respectively. Three main causes of mangrove forest destruction in Cambodia (salt farming, charcoal production and shrimp farming) have been perceived based on the literature review. Reforestation of mangrove species, banning on illegal charcoal production and deactivation of non-profitable aquaculture ponds are some of the key factors that are believed to have caused a reduction in mangrove loss in recent years in Cambodia. 

Main Results and Conclusions

• The loss of mangroves in Cambodia from 1989 to 2017 was extensive.
  • “Overall loss of mangrove forests between 1989 and 2017 has been estimated as 42% (1415 ha/year) in the four coastal provinces of Cambodia (Koh Kong, Kampot, Preah Sihanoukville, and Kep). Individual losses of mangrove areas in Koh Kong, Kampot, Sihanoukville and Kep during the study period were 39%, 45%, 52% and 34%, respectively.” (1)  
• Mangrove ecosystems are important all over the world, particularly in Asia.
  • “Mangrove forests in Asia are essential for the well-being of coastal communities because over 70% of [the] human population depends on coastal resources for food and employment.” (Kathiresan and Bingham, 2001) (1)
  • “Asia-Pacific region is very sensitive to climate change due to its topography and high population density in low-lying coastal areas (DasGupta and Shaw, 2017) and, therefore, the adverse effects of climate change can be server in this region. Furthermore, many Asian coastal areas are major tourist attractions and have high rate of infrastructure development (e.g. resorts) in terms of number and area. (Hanum et al. 2014)” (1)
• There are a few setbacks of using remote sensing and spatial data; this is important to take into account when reviewing the conclusions made from this data in order to stay transparent and realistic about those conclusions.
  • “…discrimination between mangrove vegetation and non-mangrove vegetation is still a difficult task, particularly in areas of mixed and diverse forests (Gupta et al. 2018) such as in Southeast Asia.” (1)            
  • “…spectral discrimination of mangroves (vegetation) from soil and water can be influenced by mixed pixels, which highly depends on the spatial resolution of the image as well as seasonal and diurnal intertidal interactions (Blasco et al. 1998; Kuenzer et al. 2011).” (1)  
• Though the Cambodian climate is perfect for mangrove ecosystems to thrive, anthropogenic activities have damaged them in severe ways.
  • “Despite the favourable conditions for mangrove habitat, anthropogenic activities, such as shrimp farming, salt fields and charcoal production and illegal exports, were considered as key factors that cause reduction in mangrove forests in Cambodia (Bann 1997).” (3)                
  • “Environmental conditions in the Cambodian coastline (and Mekong Delta in general) are favourable for mangrove habitat. Tropical monsoon climate with distinct dry (November–April) and wet (May–November) seasons exist in this region.” (3)                 
  • “The rapid expansion of fisheries in this region has raised major economic and environmental concerns in coastal management (Ahmed et al. 2007; Puthy and Kristofersson, 2007). Possible threats to Cambodia’s coastal region due to the loss of mangrove forests are tropical cyclones, storm surges, rising sea levels, coastal erosion and salt water intrusion into agricultural lands.” (3) 
• The mangroves have been depleted at an exponential rate in Cambodia.
  • “About 42% of the mangrove forests have been destroyed for the period between 1989 and 2017 along the coastline of Cambodia (Fig. 2).” (5)            
  • “In Koh Kong province, more than 26,000ha (39%) of the mangrove forests have been cleared during this period and major reduction in the area occurred in the late 1990s.”  (5)
  • “In terms of percentage loss, major changes occurred in Sihanoukville (52%), the largest coastal town in Cambodia, where 8127ha of mangrove forests have been cleared between 1989 and 2017. Decadal changes in mangrove forests along the Cambodian coast between 1989 and 2017 are summarized in Table 3.”  (5)
  • “Interestingly, the pattern of mangrove loss occurred in parallel with the expansion and decline of shrimp farming in Cambodia – i.e. moderate loss of mangrove forests between 1989 and 1994, high loss of mangrove areas during 1994–2009 and then the rate of mangrove loss in terms of area has been reduced.” (5)
• There have been efforts in recent years to offset this extensive mangrove loss in Cambodia.
  • “As the number of aquaculture ponds was reduced, charcoal production has been banned by legislation and effective community-based reforestation of mangroves has been implemented, the reduction in mangrove forests in terms of area has been reduced in recent years, particularly in Koh Kong and Kampot.” (6)    
  • “Diversification of mangrove reforestation with species diversity and planting native species can be more effective. Proper law enforcement for conservation of environmental resources, including mangrove forests, is still a challenge for the government authorities in Cambodia.” (6)

Works Cited

Ahmed, M., Boonchuwongse, P., Dechboon, W., Squires, D. 2007. Overfishing in the Gulf of
 Thailand: policy challenges and bioeconomic analysis. Environment and Development
 Economics 12: 145-172.

Bann, C. 1997. An Economic Analysis of Alternative Mangrove Management Strategies in Koh
Kong Province, Cambodia. Economy and Environment Program For Southeast Asia.
https://idl-bnc-idrc.dspacedirect.org/bitstream/handle/10625/15604/10738…
  =8

Blasco, F., Gauquelin, T., Rasolofoharinoro, M., Denis, J., Aizpuru, M., Caldairou, V. 1998.
 Recent advances in mangrove studies using remote sensing data. Marine and Freshwater
Research 49: 287-296. http://www.publish.csiro.au/mf/MF97153

DasGupta R. and R. Shaw. 2017. Mangroves in Asia-Pacific: A review of Threats and Responses. Pp. 1-16. In: DasGupta R., Shaw R. (eds) Participatory Mangrove Management in a Changing Climate. Disaster Risk Reduction (Methods, Approaches and Practices). Springer, Tokyo
https://link.springer.com/chapter/10.1007%2F978-4-431-56481-2_1

Gupta, K., Mukhopadhyay, A., Giri, S., Chanda, A., Datta Majumdar, S., Samanta, S., Mitra, D.,
Samal, R., N., Pattnaik, A., K., Hazra, S. 2018. An index for discrimination of mangroves
form non-mangroves using LANDSAT 8 OLI imagery. MethodsX. 5: 1129-1139.
https://www.sciencedirect.com/science/article/pii/S2215016118301535?via%…

Hanum, F., Latiff, I., Hakeem, A., Ozturk, K., R. 2014. Mangrove Ecosystems of Asia-Status.
 Challenges and Management Strategies. Springer Verlag, New York: 473.
Kathiresan, K., Bingham, B. L. 2001. Biology of mangroves and mangrove ecosystems.
 Advances in Marine Biology 40: 81-251.
https://www.sciencedirect.com/science/article/pii/S0065288101400034?via%…

Kuenzer, C., Bluemel, A., Gebhardt, S., Vo Quoc, T., Dech, S. 2011. Remote Sensing of
Mangrove Ecosystems: A Review. Remote Sensing 3: 878-928.
https://www.mdpi.com/2072-4292/3/5/878

Puthy, E. M., Kristofersson, D. M. 2007. Marine Fisheries Resource Management Potential For
 Macherel Fisheries Of Cambodia. The United Nations University: Fisheries Training
 Program. http://www.unuftp.is/static/fellows/document/puthy07prf.pdf

Veettil, B. K. and N. X. Quang. 2019. Mangrove forests of Cambodia: Recent changes and future threats. Ocean and Coastal Management 181: 104895.
https://www.sciencedirect.com/science/article/pii/S0272771418307595