This research project has been focused on the recent environmental evolution of the Urdaibai salt marshes as a result of the human occupation of these areas with agricultural purposes (18th and 19th centuries) and their later abandonment during the 20th century, and also to study their response to the small oscillations in sea level detected during the last decades as a consequence of the climate change in progress. On the other side, the creation of transfer functions based on organisms with a high potential of geological preservation (foraminifera) able to relate species and assemblages present in different salt marsh areas with their marine inundation level suppose a powerful tool to apply in the precise reconstruction of sea-level and climate variations registered in the recent geological record.