Artisanal small-scale gold mining (ASGM) using mercury affects community agreements for the conservation of forests (CoS) and lakes (CoH), which have a high level of biodiversity in the Peasant Reserve Zone of the Cimitarra River Valley (ZRC-VRC) in Colombia. In this research, a multi-criteria approach (MCA) was applied to analyze the impact of ASGM. This analysis is based on the community environmental agreements to preserve CoS and CoH areas, the ecological importance of these areas, as well as the results of mercury dispersion in the Cimitarra river basin, with concentrations found 40 km downstream of the mining area of 0.09 µgTHg L−1 in the Cimitarra river, 0.07 µgTHg L−1 in the CoH, and 0.01 mgTHg kg−1 in the tissues of macrophytes, as well as the increase in deforestation since 2020 in the CoS, due to a 1.8% (990 ha) loss of forest cover, with 693 ha of the forest cover loss coinciding with areas related to the opening of new mines. The MCA showed that the main impact is found within the criterion Social and armed conflict, followed by Deforestation. This research offers recommendations to reduce impact scores, such as the implementation of a sustainable development plan (PDS) of the ZRC-VRC, and it highlights the urgent need to safeguard the community conservation areas.
