Drivers of seedling establishment success in dryland restoration efforts

Authors: SHACKELFORD, NANCY - University Of Victoria; PATERNO, GUSTAVO - Universidade Federal Do Rio Grande Do Norte (UFRN); WINKLER, DANIEL - Us Geological Survey (USGS); Porensky, Lauren; Boyd, Chad; Clements, Teddy; Espeland, Erin; Monaco, Thomas; Rinella, Matthew - Matt

Submitted to: Nature Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/2021
Publication Date: 7/22/2021
Citation: Shackelford, N., Paterno, G.B., Winkler, D.E., Porensky, L.M., Boyd, C.S., Clements, T.C., Espeland, E.K., Monaco, T.A., Rinella, M.J., Munson, S.M., Ballenger, E.A., Quiroga, R., Wainwright, C.E., Bahm, M.A., Barger, N., Baughman, O.W., Becker, C., Esteban Lucas-Borja, M., Calleja, E., Caruana, A., Davies, K.W., Deák, B., Drake, J., Dallau, S., Eldridge, J., Farrell, H.L., Fick, S.E., Garbowski, M., de la Riva, E., Golos, P.J., Grey, P.A., Heydenrych, B., Holmes, P.M., James, J.J., Jonas-Bratten, J., Kiss, R., Kramer, A.T., Larson, J.E., Lorite, J., Mayence, C., Merino-Martín, L., Miglécz, T., Montalvo, A.M., Navarro-Cano, J.A., Paschke, M.W., Luis Peri, P., Pokorny, M.L., Saayman, N., Schantz, M.C., Parkhurst, T., Seabloom, E.W., Stuble, K.L., Uselman, S.M., Valkó, O., Veblen, K., Wilson, S., Wong, M., Xu, Z., Suding, K.L., Svejcar, L.N., Erickson, T.E., Leger, E.A., Breed, M.F., Faist, A.M., Harrison, P.A., Curran, M.F., Guo, Q., Kirmer, A., Law, D.J., Mganga, K.Z., Török, P., Abdullahi, A., Carrick, P.J., Burton, C., Burton, P.J. 2021. Drivers of seedling establishment success in dryland restoration efforts. Nature Ecology and Evolution. 5:1283-1290. https://doi.org/10.1038/s41559-021-01510-3.
DOI: https://doi.org/10.1038/s41559-021-01510-3

Interpretive Summary: Restoration ecology is rapidly advancing in response to the ever-expanding global decline in ecosystem integrity and its associated socio-economic repercussions. Nowhere are these dynamics more evident than in drylands, which help sustain 39% of the world’s human population, but remain some of the most difficult areas to restore. Restoration of degraded dryland ecosystems is frequently constrained by low and variable precipitation, extreme temperatures, relatively low soil fertility, seed quality and availability and a prevalence of invasive species. As a result, successful establishment of seeded species in dryland restoration projects may be as low as 1%. Despite these challenges, only a small fraction of terrestrial ecology (6%) and restoration studies (<5%) are conducted in drylands. We examined restoration seeding outcomes across 174 sites on six continents. Seeding had a positive impact on species presence, with almost a third of all treatments recording 100% of species seeded were present at first monitoring. Across projects, higher seeding rates and larger seed sizes resulted in a greater probability of recruitment, with further influences on species success including site aridity, taxonomic identity and species life form. Our findings suggest that investigations examining these predictive factors will yield more effective and informed restoration decision-making.

Technical Abstract: Restoration of degraded drylands is urgently needed to mitigate climate change, reverse desertification and secure livelihoods for the two billion people who live in these areas. Bold global targets have been set for dryland restoration to restore millions of hectares of degraded land. These targets have been questioned as overly ambitious, but without a global evaluation of successes and failures it is impossible to gauge feasibility. Here we examine restoration seeding outcomes across 174 sites on six continents, encompassing 594,065 observations of 671 plant species. Our findings suggest reasons for optimism. Seeding had a positive impact on species presence: in almost a third of all treatments, 100% of species seeded were growing at first monitoring. However, dryland restoration is risky: 17% of projects failed, with no establishment of any seeded species, and consistent declines were found in seeded species as projects matured. Across projects, higher seeding rates and larger seed sizes resulted in a greater probability of recruitment, with further influences on species success including site aridity, taxonomic identity and species life form. Our findings suggest that investigations examining these predictive factors will yield more effective and informed restoration decision-making.