Grasslands worldwide are being degraded via combined effects of climate change, overgrazing, and invasive species. The terrestrial application of biosolids, the stabilized and pathogen-treated remains from wastewater treatment, positively affect soil moisture retention and physical properties, while also providing nutrients that lead to dramatic increases in plant growth. The impacts of these applications on animals are poorly understood. We worked on a large cattle ranch in the interior of British Columbia, Canada, where biosolids are applied to remediate pastures after a century of cattle grazing. We examined insects, small mammals, songbirds, grouse, corvids, and raptors, to test the primary hypothesis that the bottom-up nutrient flush provided by biosolids would support higher densities or strong habitat selection for most species.
Results/Conclusions
Pastures with biosolids supported higher densities of Orthoptera (~5.6 fold), some moths, and songbirds (~50% higher), but lower densities of deermice (Peromyscus maniculatus). American Kestrels (Falco sparverius) and short-eared owls (Asio flammeus) selected nest sites on or near pastures amended with biosolids, and blue grouse (Dendragapus obscurus) hens with chicks preferentially foraged in biosolids-amended pastures. Ravens (Corvus corax) and magpies (Pica hudsonia) used biosolids-amended pastures proportionally to their abundance on the landscape, but crows (Corvus brachyrhynchos) strongly avoided amended pastures. In many cases, years-since application affected the strength of the response, sometimes with the most striking effects several years after the application. Collectively, our results signal that biosolids have strong multi-year impacts on animals, including positive effects on some bird species that are of conservation concern in British Columbia. It is thus possible biosolids could be a useful restoration tool for at-risk invertebrates and vertebrates as well as plants.