Although the potential for community-conserved areas (CCAs) to extend conservation beyond formal protected areas is widely acknowledged, the scarcity of conservation assessments and monitoring hinders the rigorous evaluation of their effectiveness in many regions. In India, which hosts a high density and diversity of CCAs, the need for more assessments of the ecological and socio- economic properties of these systems to guide conservation planning and policy has been emphasized in recent years. We inventoried the extant sacred grove network against official records of 407 groves across 70 villages in the Kodagu District of India's Western Ghats, and interviewed local communities about their management and conservation. We also evaluated recent trends in aboveground biomass of sacred groves using time-series satellite data from six time-points during the 2000-2010 period, and made comparisons to corresponding trends in nearby State-managed protected forests. Although most of the larger (> 2ha) groves officially listed were forested at present, over two-thirds of the smaller groves listed were either not forested or could not be located. Local communities attributed these declines to encroachment and illicit logging. Time-series satellite data revealed aboveground biomass declines of ~0.5% annually across the sacred grove network over the 2000-2010 period. In contrast, biomass increased during this period at the interiors and edges of State-managed forests in the landscape. Our results highlight that the conservation status of even well-protected CCAs can vary considerably over time, especially given the dynamism in socio-economic, cultural and ecological factors that govern their status. We argue that understanding and addressing this dynamism is crucial to the conservation of CCAs.