Argentinean Wetlands Through Time: A Chronicle of 100 Years of Botanical History in Buenos Aires Province

Wetlands are among the most threatened ecosystems worldwide, facing pressure from land-use change, hydrological alterations, and biological invasions. Historical vegetation records provide a valuable resource for assessing long-term changes in these environments. In this study, we evaluated the conservation status of wetlands in the province of Buenos Aires using vascular plant occurrence records, spanning more than two centuries of information (1819–2025). Records were spatially filtered using wetland maps and classified into five regions and three time periods. A database comprising 6,360 specimens, corresponding to 986 species was compiled. Species were categorized by origin, growth form, and life cycle. Conservation status was assessed using a modified Oviedo–Prieto Conservation Index (CI). Results showed that the highest floristic richness occurred in the Buenos Aires Delta, while the lowest was recorded in the Central Monte wetlands. Perennial herbs predominated, and although native species remained dominant, exotic taxa increased exponentially over time. The overall conservation index declined from 0.69 in the earliest period to 0.50 in the most recent one, indicating a progressive deterioration of wetland conservation status. Regional analyses showed the same downward trend, related to sampling intensity and land-use pressures. Diversity analyses based on the Shannon index revealed moderate to high levels of diversity, with increasing values over time in some areas, particularly in the Pampas and Coastal wetlands. This framework provides a transferable methodology for assessing wetland conservation status in other regions. Such approaches can support monitoring programs, inform management decisions, and guide conservation planning in wetlands worldwide.