By Karen E. Hodges, University of British Columbia Okanagan, Kelowna, B.C. & Frank I. Doyle, Wildlife Dynamics Consulting, Inc., Terrace, B.C.
Globally, the published work on wildlife responses to terrestrial grassland application of biosolids is limited and of questionable utility for western North America. The extant literature is derived from different regions (Missouri, North Carolina; Brown et al. 2002, Washburn et al. 2011) and ecosystems (forests, Cheng et al. 1996), or has modeled potential exposure routes for substances such as triclosan that might transfer from biosolids to animals (Fuchsman et al. 2010). In British Columbia, Metro Vancouver manages liquid waste and the resulting biosolids from 21 municipalities in the lower mainland, and is a leader in land-based applications for biosolids. Metro Vancouver has contracted SYLVIS to apply biosolids to grasslands on the OK Ranch near Jesmond BC. These grassland applications have led to clear changes in plant and soil communities (Newman et al. 2014, Wallace et al. 2016, Avery et al. 2018, 2019).
Since 2016, we and a number of BSc and MSc students have investigated how insects, birds, and mammals have responded to the addition of biosolids to the rangelands of the OK Ranch. For insects and small mammals, we’ve contrasted pastures with biosolids applied in different years to pastures with no biosolids applications.
For example, Conor McCune (BSc) examined moths in summer 2019, on pastures with biosolids applied in 2017 or 2018, contrasted with pastures with no biosolids (McCune et al., manuscript in prep). His work resulted in capturing 9889 moths, of which 2839 (30.2%) were macromoths that he identified to 57 different species. Over-all, pastures had similar numbers of species of macromoth (~25 species per sampled pasture), and over-all abundances were similar, but there were shifts in abundance of the most common species: the 2017 biosolids sites had about twice as many of the most common moth species (Euxoa servitus) as did the control sites. These results suggest there may be shifts in moth communities with biosolids applications, echoing earlier results we found with grasshoppers (Gaudreault et al. 2019). We have a large collection of beetles that we are also now identifying in the lab, to see what shifts in abundance and species we observe relative to biosolids applications. These groups of insects are important as pollinators, herbivores, and as prey for other species.
Obtaining insect data is important for understanding the responses of insectivorous songbirds and small mammals to biosolids applications. Because insects are important prey, mammals and birds may respond to both the shifts in vegetative structure that biosolids induce and to the changed prey base. We have several years of songbird data (abundance, species, some nest locations) that we are currently analyzing; early looks at the data suggest higher songbird numbers on sites with biosolids. We also just celebrated the MSc defense of Jennifer Meineke—she documented high deermouse numbers on control sites in comparison to sites with biosolids (Meineke 2020). This result confirms that control sites are more degraded, since deermice prefer sites with more bare ground, unlike the vole species, which prefer more thickly vegetated sites. During 2019, we captured very few voles since it was during a vole cycle population low. We’re currently analyzing live-trapping data from 2020 to further explore impacts of biosolids on voles and mice.
These insect, bird, and small mammal changes also affect the birds of prey. We’ve documented Long-eared Owls and Short-eared Owls nesting at the OK Ranch (Ormrod et al. in review). These birds are nomads—they migrate thousands of kilometers each year, and settle to breed in areas where small mammal prey are locally abundant. We’ve found both species in 2017 and 2020, years when cyclic voles were at population peaks or increasing. Both species nested in areas in or near biosolids-amended pastures. Short-eared Owls also were observed using biosolids-amended pastures about twice as often as expected from the availability of such pastures. We’ve dissected hundreds of regurgitated pellets from the owls, kestrels, Northern Harriers, and ravens, crows, and magpies, to see what these species are eating over the years (Meineke 2020). The picture that emerges is heavy use of small mammals (voles, mostly, not as many mice) and grasshoppers—which are much more common on sites with biosolids. Some small birds are also eaten.
Collectively, the picture we are assembling is that biosolids affect the entire food web. We’re seeing shifts in three major groups of insects. Mice, voles, and songbirds are showing changes numbers in response to biosolids. Some of the birds of prey show clear habitat selection for sites with biosolids, as well as consuming invertebrate and vertebrate prey affected by biosolids. Some of our results suggest population increases, or positive habitat selection, on sites with biosolids compared to controls. These early results suggest that further documenting the impacts of biosolids applications on wildlife species at the OK Ranch would help Metro Vancouver and others to see if biosolids could be used as a restoration tool to enhance invertebrate and vertebrate species on previously overgrazed or degraded grasslands.
Thus our work provides a comprehensive system-wide look at insect and vertebrate responses to the broad-scale application of biosolids to degraded rangelands. Our work details population and community responses of a number of species, identifies a number of vertebrate species-at-risk that use the biosolids-amended pastures, and draws together a food web analysis of biosolids-amended areas. These results are unique in the biosolids-wildlife research literature, and is expanding our understanding of how biosolids impact animals. It is possible, for example, that biosolids could be used in restoration efforts to support vertebrate species at risk of extinction, as the soil and plant changes induced by biosolids ramify through the food web. We hope such research may develop on sites that are explicitly targeted for restoration and biodiversity conservation to see how well our results apply in other settings.
Avery, E., Krzic, M., Wallace, B., Newman R. F., Smukler, S. M., and Bradfield, G. E. (2018). One-time application of biosolids to ungrazed semiarid rangelands: 14 yr soil responses. Canadian Journal of Soil Science 98:696-708.
Avery, E., Krzic, M., Wallace, B. M., Newman, R. F., Bradfield G. E., and Smukler S. M. (2019). Plants species composition and forage production 14 yr after biosolids application and grazing exclusion. Rangeland Ecology and Management 72:996-1004.
Brown, S., R.L. Chaney, M. Sprenger, and H. Compton. 2002. Assessing impact to wildlife at biosolids remediated sites. Biocycle 43: 50-58.
Buers, M., F.I. Doyle, K.J. Lawson, and K.E. Hodges. 2019. Effects of biosolids amendments on American Kestrel nest site selection and diet. Canadian Journal of Zoology 97: 1186–1194.
Cheng, C., J.P. Kimmins, and T.P. Sullivan. 1996. Forest fertilization with biosolids: impact on small mammal population dynamics. Northwest Science 70:252-261.
Fuchsman, P., J. Lyndall, M. Bock, D. Lauren, T. Barber, K. Leigh, E. Perruchon, and M. Capdeviellek. 2010. Terrestrial ecological risk evaluation for triclosan in land-applied biosolids. Integrated Environmental Assessment and Management 6:405-418.
Gaudreault, E., R.G. Lalonde, K.J. Lawson, F.I. Doyle, and K.E. Hodges. 2019. Effects of biosolids application on grasshopper [Orthoptera: Acrididae] abundance and diversity in a northern grassland. Rangeland Ecology 41:55-64.
McCune, C., F.I. Doyle, and K.E. Hodges. Grassland moth communities in relation in terrestrial applications of biosolids. Manuscript in preparation.
Meineke, J. 2020. Effects of biosolids on a grassland community of rodents and birds of prey in British Columbia. MSc, University of British Columbia Okanagan, Kelowna BC.
Newman, R., M. Krzic, and B.M. Wallace. 2014. Differing effects of biosolids on native plants in grasslands of Southern British Columbia. Journal of Environmental Quality 43:1672-1678.
Ormrod, A., F.I. Doyle, K.J. Lawson, and K.E. Hodges. Diets of avian predators in northern grasslands amended with biosolids. In review at Ecology and Evolution.
Wallace, B.M., M. Krzic, R.F. Newman, T.A. Forge, K. Broersma, and G. Neilsen. 2016. Soil aggregate dynamics and plant community response after biosolids application in a semiarid grassland. Journal of Environmental Quality 45: 1663-1671.
Washburn, B.E. and M. Begier. 2011. Wildlife responses to long-term application of biosolids to grasslands in North Carolina. Rangeland Ecology and Management 64:131-138.