A regional map of mangrove extent for Myanmar, Thailand, and Cambodia shows losses of 44% by 1996

Southeast Asia is home to some of the planet’s most carbon-dense and biodiverse mangrove ecosystems. There is still much uncertainty with regards to the timing and magnitude of changes in mangrove cover over the past 50 years. While there are several regional to global maps of mangrove extent in Southeast Asia over the past two decades, data prior to the mid-1990s is limited due to the scarcity of Earth Observation (EO) data of sufficient quality and the historical limitations to publicly available EO. Due to this literature gap and research demand in Southeast Asia, we conducted a classification of mangrove extent using Landsat 1-2 MSS Tier 2 data from 1972 to 1977 for three Southeast Asian countries: Myanmar, Thailand, and Cambodia. Mangrove extent land cover maps were generated using a Random Forest machine learning algorithm that effectively mapped a total of 15,420.51 km2. Accuracy assessments indicated that the classification for the mangrove and non-mangrove class had a producer’s accuracy of 80% and 98% user’s accuracy of 90% and 96%, and an overall accuracy of 95%. We found a decline of 6,830 km2 between the 1970s and 2020, showing that 44% of the mangrove area in these countries has been lost in the past 48 years. Most of this loss occurred between the 1970s and 1996; rates of deforestation declined dramatically after 1996. This study also elaborated on the nature of mangrove change within the context of the social and political ecology of each case study country. We urge the remote sensing community to empathetically consider the local need of those who depend on mangrove resources when discussing mangrove loss drivers

Climate Change Adaptation Strategies in Agriculture: Cases from Southeast Asia

Climate change has become apparent and been threatening more and more in Southeast Asia. Its impacts on agriculture and adaptation strategies at household level in farming systems areas are explored. The study focused on better understanding of climate change impacts and adaptation practices in four villages of Myanmar and Cambodia. Household questionnaire survey, focus group discussions and key informant interviews were used for data collection at household and community level supplemented with secondary data. Dry Zone farmers of Myanmar reported increase in crop diversity while in the Kampong Speu province in Cambodia, the number of rice growing farmers increased together with cultivation of other crops, such as cassava, palm fruit, sugarcane, mangoes, watermelons and vegetables. Farmers changed their cultivation practices as adaptation strategies in various ways: change in cropping calendar, crop varieties, machinery for cultivation practice, and change in area for cultivation. The shift in cropping calendar has occurred from two weeks to one month. Diverse strategies were reported in adapting to water scarcity in agriculture, such as system of rice intensification and water pumping. Farmers also adopted strategies for coping with declining soil productivity. These include animal manure application, compost making and application, crop rotation and crop residues retention. In particular, Dry Zone farmers prefer to apply animal manure rather than other practices because of its vast benefits, such as buffering capacity, effectiveness for plant growth and cheaper price. Cooperative actions are becoming increasingly needed when an individual could not afford adaptation strategies. However, barriers to adaptation strategies are to be reduced to promote climate adaptive practices in agriculture

The impacts of degradation, deforestation and restoration on mangrove ecosystem carbon stocks across Cambodia

Mangrove forest conservation can help reduce global C emissions. Despite this benefit to climate change mitigation and adaptation, mangrove forests are being deforested or degraded at an alarming rate, though restoration efforts may offset these losses. The impacts of deforestation to C stocks are relatively intuitive and result in significant decreases in C stocks. It remains unclear how degradation from selective harvesting of trees affects C stocks or how effective restoration efforts are at restoring C stocks. Furthermore, total ecosystem C (TEC) stocks of pristine mangroves can significantly vary spatially. To address these issues, we conducted an intensive, national assessment of mangrove forests across Cambodia using a grid approach to: 1) examine how land use land cover (i.e., pristine, deforested, degraded, and restored forests) impacts TEC stocks, and 2) how TEC stocks vary spatially across the country. TEC stocks from deforested mangroves were always lower than pristine forests, resulting in an overall loss of 60% C (480 Mg C ha−1). However, TEC stocks from degraded and 25-year-old restored mangroves forests did not differ from pristine forests. Mean TEC in mangroves was 784.7 ± 30.1 Mg C ha−1, decreasing from 957.2 ± 32.8 Mg C ha−1 in the northern region to 628.9 ± 33.1 Mg C ha−1 in the central region to 386.2 ± 19.1 Mg C ha−1 in the southern region of Cambodia. Intensive sampling in mangroves across Cambodia verified impacts of deforestation reported elsewhere, revealed the lack of degradation impacts on TEC stocks, and demonstrated the effectiveness of restoration on TEC stocks after only 25 years. Our gridded sampling approach was able to capture spatial variability across Cambodia and provide a more realistic TEC stock information that can be used for national reporting or participation in C markets