Small but critical: semi-natural habitat fragments promote bee abundance in cotton agroecosystems across both Brazil and the United States

Context: Bees are the most important pollinators of crops worldwide. For most bees, patches of semi-natural habitat within or adjacent to crops can provide important nesting and food resources. Despite this, land cover change is rapidly reducing the abundance of semi-natural habitat within agroecological landscapes, with potentially negative consequences for bee communities and the services they provide. Objectives: Identify how the availability of semi-natural habitat impacts bee communities across biogeographic regions, which may reveal commonalities and key governing principles that transcend a single region or taxa. Methods: We analyze and compare the drivers of bee community composition in cotton fields within Brazil and the U.S. to reveal how land cover and land cover change impact bee community composition across these two regions. Results: We show that the most critical factors impacting bee communities in cotton agroecosystems are the same in Brazil and the U.S.: bee abundance increases with cotton bloom density and the abundance of semi-natural habitat. Further, the loss of semi-natural habitat over a 5-year period negatively impacts bee abundance in both agroecosystems. Conclusions: Given the importance of bee abundance for the provision of pollination service in cotton plants, our findings highlight the significance of small semi-natural habitat fragments in supporting key ecosystem service providers for both tropical and temperate cotton agroecological systems. We underscore the important role that local land managers play in biodiversity conservation, and the potential contribution they can make to pollination provision by supporting agricultural landscapes that conserve fragments of semi-natural habitat.