Samenvatting
Long-term monitoring of faunal diversity provides the empirical foundation for understanding the magnitude, trajectory,
and drivers of biodiversity change and for designing evidence-based conservation responses. This review synthesises
evidence on long-term faunal diversity changes from monitoring programmes, resurvey studies, and historical biodiversity
databases spanning the past century, with particular reference to South Asian terrestrial and freshwater ecosystems.
Drawing on 184 published studies and 12 long-term monitoring datasets, we assess evidence for temporal trends in
species richness, abundance, functional diversity, and community composition across major taxonomic groups. The
weight of evidence confirms significant negative trends in vertebrate and invertebrate diversity globally and in South Asia,
driven primarily by habitat loss, agricultural intensification, invasive species, and climate change. However, the evidence
base is taxonomically and geographically uneven, with birds and mammals best-monitored and invertebrates, freshwater
fauna, and soil organisms severely under-represented in long-term datasets. We identify three methodological
challenges -- detectability bias, spatial scale dependence, and baseline shifting -- that complicate interpretation of
long-term diversity trends and propose minimum standards for future long-term monitoring programmes. We conclude
with a prioritised research agenda for long-term faunal diversity monitoring in South Asian ecosystems.