1. Some biofilms and biopatinas formed by lichens protect the Angkor sand-stones against direct atmospheric attacks and induce a very slow bio-chemical weathering regime: it has been scientifically demonstrated at several sites of the Angkor Archaeological Park that biodeterioration be-low forested biofilms operates 100 times more slowly than mechanical deterioration due to wetting-drying cycles at cleared sites. It is therefore strongly recommended to:
a. Carry out detailed studies on the nature and role (destructive versus protective) of biofilms before considering their eradication; a particular attention should be paid to the temporal successions of communities colonizing the stone (cf. pioneer versus mature stages).
b. Preserve the protective biofilms and the forest cover conducive to their development, which induces buffered microclimate conditions which slow down the sandstone decay (“umbrella effect”).
c. Prohibit the use of chlorine-based biocides (dangerous for the environment) and organic biocides (favouring new phases of biological colonization).
d. Prohibit any stone cleaning unless it is duly motivated, strictly regulat-ed, and preceded by a thorough study of the colonizing biofilm and substrate.
2. Everybody agreed on the necessity of establishing a Risk Map and to refer to it in every conservation and/or maintenance activity.
It is recommended that the APSARA National Authority establishes a special unit to see to the implementation of this Risk Map.
3. In Angkor, everyone has shown an interest in generalising the techniques and methodologies to be used for stone conservation.
Therefore, more teams have been put in place and more resources allocated.
It is strongly recommended that the APSARA National Authority sees to the overall coordination of all ongoing programmes and projects in order to avoid overlap and to better target the activities and their efficiencies.