Arboriculture & Urban Forestry 41(4): July 2015 leave out-of-bounds areas unmanaged and increase vegetation surrounding all water bodies (Hudson and Bird 2009), thereby acting as a refuge for flora and fauna (Yasuda and Koike 2006). • Public and residential gardens and land- scapes. Public and private landscapes, dom- inated by a diverse collection of native and introduced trees and shrubs, are substantial contributors to regional species biodiversity (Yilmaz et al. 2008; Goddard et al. 2010; Molebatsi et al. 2013; Nielsen et al. 2014). They naturally contain a high percentage of edge environments and are usually rich in plants with floral and fruit displays. These characteristics create environments that can be significant refuges for endangered plants and animals (Akinnifesi et al. 2010), and may house more species than either managed or natural areas. Botanically diverse commu- nities are less vulnerable to exotic species invasion (Mandryk and Wein 2006), and if noxious weeds do appear they are likely to be spotted and removed by landscape managers and homeowners before they can establish recalcitrant populations. CONCLUSIONS It is challenging to engage homeowners and land- scape managers on the issue of landscape biodiver- sity, simply because there is no obvious venue for doing so. Certified arborists, Extension specialists, and others should reach out to private property owners with science-based recommendations for attracting and retaining birds, pollinators, and other desirable animal species in their gardens and land- scapes. Specific, achievable actions could include: • reducing open lawn (Marzluff and Ewing 2001; Hudson and Bird 2009) and replacing it with vertically diverse vegetation (Ikin et al. 2013a) • • increasing shrub and tree cover, especially in newer neighborhoods distant from forest edges (Kalinowski et al. 2010; Ikin et al. 2013a) selecting both native and noninvasive, intro- duced trees and shrubs to increase plant diversity (Raupp et al. 2006) and aesthetics 181 • planting fruit-bearing trees, shrubs, and ground covers for human and animal con- sumption alike (Campbell and Campbell 2001) • adding a permanent water feature when feasible These science-based recommendations for increasing species biodiversity in urban land- scapes stand in stark contrast to the list of char- acteristics used to promote the exclusive use of native plant species. This review demonstrates that nonnative plants will attract and retain beneficial wildlife, including birds, insects, mammals, and reptiles; furthermore, by expanding the accept- able list of landscape trees and shrubs, biological and genetic diversity are enhanced. An additional benefit is that biodiverse landscapes have been positively linked to self-perceived well-being of neighborhood residents. (Luck et al. 2011). Science-informed decisionmaking must occur in the planning and designing of urban green- spaces as well as in the selection and management of woody species. To paraphrase Sagoff (2005) and Davis et al. (2011), it is time for urban planners to focus on the function of tree species, not on their origin. Urban planners should engage landscape professionals and applied plant scientists in their process so that current, relevant, research-based information can be considered. The message is simple and straightforward: a natives-only tree policy sharply reduces the planting palette and ultimately community biodiversity of urban areas. Acknowledgments. I am most appreciative of the comments and suggestions made by two anonymous reviewers and the associate editor. LITERATURE CITED Adhikari, Y.P., A. Fischer, and H.S. Fischer. 2012a. Micro-site condi- tions of epiphytic orchids in a human impact gradient in Kath- mandu Valley, Nepal. Journal of Mountain Science 9:331–342. Adhikari, Y.P., H.S. Fischer, and A. Fischer. 2012b. Host tree utili- zation by epiphytic orchids in different land-use intensities in Kathmandu Valley, Nepal. Plant Ecology 213:1393–1412. Akinnifesi, F.K., G.W. Sileshi, O.C. Ajayi, A.I. Akinnifesi, E.G. de Moura, J.F.P. Linhares, and I. Rodrigues. 2010. Biodiversity of the urban homegardens of So Luis City, Northeastern Brazil. Urban Ecosystems 13:129–146. Andrade-Núñez, M.J., and T.M. Aide. 2010. Effects of habitat and landscape characteristics on medium and large mammal spe- cies richness and composition in northern Uruguay. Zoologia 27:909–917. ©2015 International Society of Arboriculture
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