Recent changes in tropical-dry-forest connectivity within the Balsas Basin Biogeographic Province: potential effects on endemic-bird distributions

Maintaining landscape connectivity is a conservation priority for biodiversity as it may mitigate the adverse effects of forest degradation, fragmentation, and climate change by facilitating species dispersal. Despite their importance for biodiversity conservation, Mexican tropical dry forests (TDFs) face high fragmentation rates due to anthropogenic activities. In this study, we analyzed the connectivity dynamics of TDFs in the Balsas Basin Biogeographic Province (BBBP) between 2013 and 2018, focusing on old-growth and secondary TDF covers, including Protected Areas and Important Bird Areas. We evaluated the effects of connectivity loss and gain on the distribution areas of 30 endemic bird species with ecological associations with TDFs in the BBBP. We found expansion in TDFs accounting for a total increase of 227,905 ha due to secondary forest increase (12%). In contrast, old-growth forests experienced a reduction of 66,576 ha in the study area (8%). We also found a decrease in areas with high and very-high connectivity, coupled with an increase in low connectivity, except for TDFs inside Protected Areas, which increased by 3,000 ha, leading to higher connectivity. There was an increase in total forest cover in 27 species’ potential distribution, highlighting the possible role of secondary forests in promoting connectivity between old-growth forest patches. Our results reveal the complex dynamics between forest types, connectivity, and bird-species distributions. Despite an overall increase in forested areas, most TDFs continue to have low connectivity, likely impacting biodiversity, particularly for species that rely on highly conserved ecosystems. This study underscores the importance of integrated conservation strategies considering connectivity, forest recovery, and the dynamics of species-ecosystem interactions.