Conservation opportunities for threatened paleochannel grasslands in the South American Dry Chaco

Subtropical drylands, such as the South American Dry Chaco, harbor azonal grasslands in ancient river beds (hereafter, paleochannels). These grasslands host high biodiversity and provide numerous ecosystem services. However, cultivated systems often replace paleochannels grasslands due to their biophysical characteristics and low investment requirements. Furthermore, there is a lack of basic characterization of paleochannel grasslands due to their complexity, which challenges their conservation. Here, we mapped and described for the first time the paleochannel grasslands of the Argentinean Dry Chaco based on their current land cover, spatial configuration, EVI values (a proxy for primary productivity), fragmentation, and protection. We speculate that natural (i.e., shrub encroachment enhanced by overgrazing and fire management prohibition) and anthropogenic processes (i.e., farming and infrastructure) have transformed the Argentinean Dry Chaco grasslands into woody-dominated or agricultural systems. Therefore, while grasslands in low-transformation matrices were mainly replaced by shrubs, those in high-transformation matrices were integrated into agricultural landscapes (i.e., whole units fragmented by croplands and roads). However, paleochannels in medium-transformation matrices showed the highest grassland cover, EVI values, and intermediate fragmentation level. Located in the NW of the Argentinean Dry Chaco, this group of paleochannels should be prioritized in future conservation and management strategies, as currently is not included in any protection scheme. Our work highlights the need to include non-pristine systems that have received perturbation in the past in conservation actions to mitigate and reduce the degradation of threatened dryland habitats.