City Trees is a premier publication focused on urban + community forestry. In each issue, you’ll learn how to best manage the trees in your community and more!
Issue link: http://read.dmtmag.com/i/648999
Chile has certain geographical characteristics that make it particularly vulnerable to flooding from rivers. On March 24, 2015, an unusual storm in the driest desert in the world—the Atacama region in northern Chile—triggered a series of floods that devastated several localities, including the city of Copiapó. The overflowing of the Copiapó River flooded the city with mud, dramatically affecting the local infrastructure and the lives of its inhabitants. Trees also suffered—the mudslide was a stroke of the sword through the heart of numerous woody warriors. Less than a year after the floods, palm trees (Phoenix canariensis and others), silver wattles (Acacia dealbata), oriental planes (P. orientalis) and peppers (Schinus molle) began to fall. Before the flood, they had already been weakened by age, heavy soils and arid conditions. After the flood, the accumulation of polluted, dried mud around tree trunks and over tree roots prevented water infiltration. Just eight months after the flood, the wind had dealt the final blow to more than 30 of these weakened trees, with more losses likely yet to come. My colleagues in Copiapó and throughout Chile want to prevent this kind of disaster in the future. We can install water collectors and dikes and other barriers, forest the foothills, improve the urban design of settlements, avoid settlements in inappropriate places, plant species resistant to flooding, and promote green infrastructure. But sometimes, even with these preparations, irrepressible threats will come, and reverently we understand that nature manages to impose its terms. —Felipe Fuentes R., Municipal Arborist for I. Municipalidad de Calera de Tango, Chile To give some background: our company, Valley Tree and Landscape, has planted more than 25,000 trees for greater New York City over the course of 25 years. In October 2012, Hurricane Sandy hit Long Beach, Long Island with several feet of salt water on land, bay to ocean, for about 12 hours, accom- panied by high winds. That brief flooding event left dramatic damage to the region's trees, with some surprising victims. The biggest shock was how poorly Long Island's many London plane trees (Platanus x acerifolia) fared. We had long thought them to be flood and salt tolerant and they had been widely advocated for seaside use. The damage manifested in stages; the following spring, an average of a third of the canopy was affected. It wasn't typical dieback, in that it didn't affect the whole crown. A large section of the crown on one side would not break bud, while the rest leafed out normally. However, over the 2013 growing season, the trees continued to show signs of decline, until by 2014 their bark started to peel off and the trees died. In the summer of 2014, Long Beach took down more than 1400 dead trees. My guess is that 85 percent or more of them were London planes. We used to have our streets lined with allées of them, like American elms (Ulmus americana) back in the day. This was a huge blow to our city. Lesson learned: the city will avoid planting monocultures in the future, no matter how flood-tolerant any one tree species is thought to be. Arborvitaes (Thuja spp.) in our area were instantly killed by the floods, as were blue atlas cedars (Cedrus atlantica). I had a job where I'd planted 200 blue atlas cedars at 4-inch caliper, and they were at 7-inch caliper when the storm came; they were dead within weeks. That was heartbreaking. Leland cypress- es (Cupressus x leylandii) also were quick to die. Tulip trees (Liriodendron tulipifera) never put leaf on again. Every single Japanese maple (A. palmatum) died. Pine trees (Pinus spp.) and magnolias (Magnolia spp.) were a mixed bag. Across spe- cies, mortality was high for newly planted/younger trees. There were happy surprises, though. Blue spruces (Picea pun- gens) never looked better; no one expected that! Junipers (Juniperus spp.) and red cedars (T. plicata) did fine, as did holly trees. The Kwanzan cherry trees (Prunus serrulata 'Kwanzan') When one thinks about the City of Miami Beach, vivid images come to mind: sparkling water, sandy beaches, signifi- cant art and cultural events, and palm-lined streets. However, some of the features that make Miami Beach such a prime des- tination also include some notable concerns. Geographically speaking, the City is a coastal spoil island (an island created by waterway dredging) with a fairly low elevation and high brackish ground water tables. This has led to a history of storm and salt water tidal flooding events most notably during the "king tides" (exceptionally high tides that occur a few times per year). To address the significant issues caused by storm-related flooding, sea level rise, and high tides, the City has embraced a new comprehensive strategy. It includes additional storm water pumping stations, raised sea wall and road elevation projects, adoption of a robust climate resiliency plan, and revisions to the City's reforestation program, including planting standards. Integrating what was learned from Sandy's particular toll, we identified a list of 75 tree species and cultivars that the City considers worthy of use in the advisory flood zone for a one percent storm. Every new tree planted within the flood zone will now be chosen from the refined palette to ensure our trees are long-lived and resilient. Those trees include species and cultivars of hedge and red maple (A. campestre and A. rubrum), birch (Betula spp.), hackberry (Celtis occidentalis), hawthorn (Crataegus spp.), coffeetree (Gymnocladus dioicus), elm (Ulmus spp.), oak (Quercus spp.), blackgum (Nyssa sylvat- ica), and zelkova. —Matthew Stephens, Former NYC Parks and Recreation Director of Street Tree Planting did okay if they'd been in the ground at least three years. Honeylocusts (Gleditsia triacanthos) and pears (Pyrus spp.) did okay, and Norway maples (A. platanoides) and zelkovas (Zelkova serrata) did well. —Joel Greifenberger, Owner of Valley Tree and Landscape in Long Beach, Long Island 20 City Trees