Exploring soil erosion in the lake basins of Michoacán, Mexico: From sediment cores to conservation policies

Understanding soil erosion, its history and links to potential drivers such as land use (particularly agriculture and deforestation), different cultural perspectives and climate change are crucial for the development of effective management and conservation strategies. Here, we explore soil erosion in two lake basins, Pátzcuaro and Zirahuen, in the highlands of Michoacán, Mexico, weaving together scientific enquiry (including lake sediment studies and monitoring data) and cultural–historical perspectives based on documentary sources. Both lake basins are within the Trans Mexican Volcanic Belt, lying at >2000 m a.s.l. Pátzcuaro is large, but shallow, while Zirahuen is smaller, but deep. Archaeological evidence for long-term human occupation is clearer for Pátzcuaro. Pátzcuaro is known for severe degradation of both the catchment and the lake, while Zirahuen has, until recently, been regarded as less disturbed. The relative impacts of pre-Hispanic and post-Hispanic practices have been the subject of debates across the disciplines and have impacted approaches to conservation, particularly attitudes to indigenous land use practices. Palaeoenvironmental records highlight human impact on these basins, often expressed as periods of accelerated erosion in response to forest clearance, over at least 3500 years. This shows that neither can be regarded as pristine and were not pristine at the time of the Conquest. As well as responding to varying intensities of land use, often linked to population change, erosion relates to climate, but is also affected by cultural and socio-economic contexts and discourses. Historical documents show that concerns about deforestation and erosion have influenced the development of forest conservation policies, in the context of government reforms, tensions between agricultural expansion and forest conservation, and the growth of scientific research in limnology. These policies have also been shaped by changing cultural discourses regarding indigenous land management practices. The value of taking an holistic approach to understanding erosion is emphasized.