Human impacts on geodiversity and associated natural values of bedrock hills in the Mekong Delta

The isolated hills that rise above the plains of the Mekong Delta contribute significantly to geodiversity and are fundamental to the retention of biodiversity and ecosystem services. As the only topographic highpoints on the delta, these hills, together with caves some hills contain, have long formed a natural focus for human attention and activity. They have provided important sites for habitation, spiritual practices, production of timber, agricultural fertilizer, and building stone and cement and have been the arena of multiple episodes of armed conflict. These uses have degraded the natural environmental values but in some cases led to accrual of cultural heritage value that has accentuated recently growing pressures from recreation and commercial tourism. Habitation, religious use, and tourism have caused significant but localized soil loss, while cave systems have been damaged by trampling, hydrological changes, removal and mixing of sediments, and damage to speleothems. Impacts caused by armed conflict have been much more widespread and include damage to rock surfaces, soils, and caves by deployment of explosive and other ordnance and the establishment of infrastructure in caves including weapons caches, defensive structure, and cave hospitals. Quarrying for building materials has resulted in very pronounced landform modification with recent expansion of cement manufacture entailing the removal of entire hills. The very limited extent of these upland environments on the Mekong delta and the particular importance of some values at stake greatly intensify the significance of human impacts on both their geoheritage and the other natural values that are dependent upon it.