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
New York City lost at least 11,000 street trees (and an estimated more than 10,000 park trees) to storm damage from Sandy and shared with Long Island the experience of signifi- cant die-off of London plane trees. NYC Parks and Recreation prepared a report after Sandy related to flooding. With regard to London planes, more than 1500 failed to leaf out at all the following season and more than 2500 leafed out 50 percent at best, with further decline anticipated. Part of that report asks, "How will we change what we plant because of Hurricane Sandy?" Sandy highlighted that we as urban forest managers must con- tinue to be vigilant in our efforts to specify trees that will be resilient to not only a diverse array of urban factors, but also changing environmental factors. For example, going forward, trees we choose to plant within the advisory flood zone for a one percent storm must be tolerant of both coastal conditions as well as inundation. To give you an idea of how important this consideration is, fourteen percent of NYC streets fall within the advisory flood zone. Like many cities that had to replace much of their canopy after losing trees to Dutch Elm Disease, the most common street trees in the city are maple (Acer spp.) and ash (Fraxinus spp.). Together, they make up 70 percent of the urban canopy in Cedar Rapids. The overwhelming majority of the trees lost to flooding consisted of these species. If there is a silver lining to the flood and its aftermath, it is that we are now able to start to provide a better quality urban forest for future generations. The looming threat of Emerald Ash Borer also affected these areas. Starting in 2009, the city began proactively removing ash. Since we were losing such a large number of trees from the flood and the majority of the homes were condemned and scheduled for demolition, these neighborhoods were among the first targeted for the ash tree removal program. Unlike other target areas, all ash in these neighborhoods were removed. The City reforestation budget allows for 1000 new trees to be planted yearly. Replacement trees are pulled from an ever-changing list of 60 different species, a practice helping to create a more diverse forest. While diversity is the primary directive for reforestation, matching species to the site is also very important. This is especially true for flood-prone areas. While this method is now adopted as part of a city-wide man- agement plan, it was initiated because of the flood. Instead of rebuilding homes in these flood-affected areas, plans are in place for a levee system to protect the city from the river that runs through it. Seven years after the flood, and three years after the mass tree removals ended, new removals have begun in preparation for the coming flood protection system. These areas will be turned into recreational green space and trees will play a big part in the design. Species selection for these areas will be a careful consideration. Another flood event is likely to happen, but this time, we will be planning for it. —Todd Fagan, City Arborist, Cedar Rapids, Iowa The toppling of streambank trees is one of the classic symptoms of "Urban Stream Syndrome," a term that covers a number of ill effects of flooding on urban waterways. What are the major reasons flooding is so pun- ishing for trees? Dr. Kamran Abdollahi, professor of forest ecophysiology in the urban forestry program at Southern University in Baton Rouge, Louisiana, explains that flooding fills soil pores, denying tree roots access to the oxygen they need for respi- ration and water and nutrient uptake. Dr. Abdollahi says, "In the urban environment where soils are already compacted by human activities, flooding exacerbates compaction and its negative effects. Flooding can also negatively affect root anchoring and tree stability." www.urban-forestry.com 19