As shown in USDA and NOAA maps, plant hardiness zones have changed and generally shifted northward in recent decades. Saltwater intrusion related to sea level rise is already causing die-off of coastal forests along the Big Bend coast (see here and Williams et al., 1999) and in the Florida Keys (see Alexander, 1976 and Ross et al., 1994), impacting freshwater supplies, and causing temperatures to hit record levels (see here). Mangrove communities are being documented further north along the Big Bend and Atlantic coastlines as temperatures change (see for example Raabe et al., 2012 and Williams et al., 2014). A primary question is if or how these changes should affect current and future planting choices by landscape architects. Issues include salt tolerance of species in coastal areas (including to increased salinity in freshwater supplies), resilience to precipitation and temperature changes, the value of choosing some native species over non-natives (for example to support native pollinators as the climate changes), potential use of new cultivars bred for salt tolerance or resistance to pests, overuse of popular species (reducing ecosystem health and resilience), and changes in distribution of invasive exotics that may become acclimated to new environments. Although the relatively short lifespan of many common landscape plants may make changes to plant pallets less important right now, it is possible that some species currently used by landscape architects will be less suitable in the future.
Feedback from practitioners highlights some lack of consensus regarding the best approach to responding to climate change through planting design. Most landscape architects agreed that salt-tolerant and resilient (water and drought tolerant) plants should be used in areas impacted by sea-level rise and/or precipitation changes. Hardy plants may also be needed to withstand temperature fluctuations, primarily warmer temperatures but possibly colder winters. Some respondents noted that plants are not high enough in value and/or are too short-lived to warrant making changes to planting palettes in response to an uncertain change in climate. Most also agreed that many climate change issues are already addressed in currently promoted landscape practices such as those outlined in the Florida-Friendly Landscaping program.
With this in mind, the literature reviewed identifies several common-sense and no-regrets planting design strategies that may be used to mitigate the impacts of climate change, while also increasing resiliency. These include water-wise and low maintenance planting choices that limit the need for irrigation and carbon emissions from gas-powered tools, incorporating a diverse range of native plants to support pollinators and wildlife, and continued/increased use of trees in designs to assist with carbon uptake, reduction of heat-island effects, and passive cooling.
Issues that will require further research include whether/how to expand the use of salt-tolerant planting in upland areas, how suitability for commonly used landscape species might change in response to precipitation and temperature fluctuations, and how future impacts from invasives might change. Included below are resources related to the use of plants to mitigate climate change impacts and potentially increase the resiliency of landscapes.
Tools
i-Tree Eco (v 6) | Landscape Performance Series
i-Tree Streets (v 5.1) | Landscape Performance Series
Web-based Resources
Florida-Friendly Landscaping
Florida-Friendly Landscaping Program: http://fyn.ifas.ufl.edu/index.html
Native Plants and Pollinators
Florida Association of Native Nurseries (information on Florida natives and nurseries): https://www.floridanativenurseries.org/
Florida Native Plant Society: https://fnps.org/
National Wildlife Federation Native Plant Finder (native plant finder for pollinator species): https://www.nwf.org/NativePlantFinder/
Institute for Regional Conservation (information on use of native plants in south Florida): https://regionalconservation.org/
Other Resources
Center for Landscape Conservation and Ecology: https://clce.ifas.ufl.edu
Florida Wildflower Foundation: https://flawildflowers.org/
Lady Bird Johnson Wildflower Center: https://www.wildflower.org/
National Wildlife Federation (gardening for climate change): www.nwf.org
U.S. Forest Service Climate Change Resource Center (urban forests and climate change): https://www.fs.usda.gov/ccrc/topics/urban-forests-and-climate-change
Research
Glick, P. (2007). The Gardener’s Guide to Global Warming: Challenges and Solutions
McPherson et al. (2013). Urban Forests and Climate Change
Missouri Botanical Gardens (research on climate change impacts to plants): http://www.missouribotanicalgarden.org
Reed and Stibolt. (2018). Climate-Wise Landscaping
Citations
Alexander, Taylor R. 1974. Evidence of Recent Sea Level Rise Derived from Ecological Studies on Key Largo, Florida. In Environments of South Florida: Present and Past, edited by Patrick. J. Gleason, 219-222. Miami, Fla.: Miami Geological Society.
Raabe, Ellen A., Laura C. Roy, and Carole C. McIvor. 2012. Tampa Bay Coastal Wetlands: Nineteenth to Twentieth Century Tidal Marsh-to-Mangrove Conversion. Estuaries and Coasts 35:1145-1162. doi:10.1007/s12237-012-9503-1
Ross, Michael S., Joseph J. O’Brien, Leonel da Silveira, and Lobo Sternberg. 1994. Sea-Level Rise and the Reduction in Pine Forests in the Florida Keys. Ecological Applications 4(1): 144-156.
Williams, Kimbelyn, Katherine C. Ewel, Richard P. Stumpf, Francis E. Putz, Thomas W. Workman. 1999. Sea-level Rise and Coastal Forest Retreat on the West Coast of Florida, USA. Ecology 80(6): 2045-2063.
Williams, Asher A., Scott F. Eastman, Wendy E. Eash-Loucks, Matthew E. Kimball, Michael L. Lehmann, and John D. Parker. 2014. Record Northernmost Endemic Mangroves on the United States Atlantic Coast with a Note on Latitudinal Migration. Southeastern Naturalist. 13(1):56-63. doi: 10.1656/058.013.0104]]>