Freshwater ecosystem transitions due to artisanal sand mining in Rwanda, Africa.

Artisanal small-scale mining (ASM) of sand, gravel and crushed stones plays an economically important role through its value as a 'development mineral' for a growing population in sub-saharan Africa. The extracted material is used in developing and expanding urban areas and infrastructure and provides income for the population involved in the sector. However, the extraction of aggregates has shown to have large and often complex ecological and socio-economical consequences with potential significant health effects on the miners and the environment in which the mining takes place. Here we show that ASM in a river channel in central Rwanda causes a systemic shift in freshwater biodiversity by changing species assemblages from being riverine towards communities representing standing waters. Based on 101 point samples, we find that ponds created due to mining activities act as habitats for freshwater insects associated with wetland habitats. Furthermore, these mining ponds did also act as breeding sites for mosquitoes and thereby potentially increase the presence of vector borne diseases such as malaria. These findings show how ASM can generate a landscape level shift in freshwater biodiversity and introduces the apparent paradox that while aggregates are critical building blocks in mitigating malaria transmissions and prevalence through improved housing, the mining practices unwillingly can create new breeding ground for malaria mosquitos, thus increasing the risk of malaria spreading to nearby communities.