Authors: Andrade-Díaz, María;Piquer-Rodríguez, María; Baldi, German;

The South American Dry Chaco harbors azonal grasslands in ancient river beds (paleochannels). These grasslands host a wide range of species and provide ecosystem and cultural services. Besides, paleochannels offer a significant economic profit with a minimum investment for their use due to high fertility, flat relief, and natural vegetation easy-to-mechanically-removal. This promotes the replacement of grasslands by cultivated landscapes. However, a lack of basic characterization of the paleochannel grasslands challenges their conservation. For the first time, we mapped and described paleochannel grasslands based on their land cover, spatial configuration, primary productivity, fragmentation, and protection. We observed that grasslands in low-transformation matrices were mainly replaced by shrubs, which increased their primary productivity. The proportion of cropland inside paleochannels increased with increasing matrix transformation, promoting a high fragmentation by croplands and roads. Moreover, the majority of paleochannel grasslands were not included in any protection scheme. Our results suggest that natural (shrub encroachment enhanced by overgrazing and fire management prohibition) and anthropogenic processes (agriculture and roads) are turning grasslands into woody-dominated or agricultural systems. Finally, we proposed a set of highly productive, grassland-dominated paleochannels located in the NW of the Dry Chaco that should be included in future conservation and management strategies.