ABSTRACT.- Grasslands are endangered habitats through the world. Among its threats, land-use change has been recognized as one of the most important drivers of biodiversity decline. Sustainable livestock farming can be important conserving grasslands and preserving their biodiversity, and particularly in Uruguay are extensive and are carried out based on natural grasslands with little external management. However, in recent years there has been an increasing in land-use change, replacing natural grasslands with cultivated pastures, leading to a homogenization of the environments. Spiders are a model group for ecological studies, because they are good indicators of environmental change. Our goals were to evaluate the effect of land-use change (natural grasslands by annual pastures) in livestock systems of Uruguay on the spider community; and describe this community identifying conservation priority species and potential environmental indicators. We collected spiders seasonally during 1 year in three farms in Uruguay with a cattle and sheep full cycle production system. We found that substitution of natural grasslands by pastures in livestock systems implied a reduction in spider abundance and species richness. We found species considered of priority conservation for the country according to a local list and added new species to that list. Implications for insect conservation:Our results highlight the importance of conservation of natural grasslands, even in productive systems, to reduce spider diversity loss, and contribute to preserve one of the most threatened environments in the region. © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG.