Why is tree diversity important?
By Jean Hansen - Sioux City Journal
An important lesson that has been learned from Dutch Elm disease and other similar catastrophic eventsis the severe consequences that occur when tree diversity is low. Tree diversity affords a shield against major tree losses when pathogens or exotic pests attack the population. In the past, trees were chosen on their aesthetics, (size, shape and color) and their ability to adapt to the environment (tolerances to temperatures, soil composition and soil moisture). Today, we not only need to consider the aesthetics of the tree and the environment that it is being planted in, but also the tree population in the geographic location.
As we look forward to the future of trees in Sioux City we must continue to diversify our tree population. Fifteen years ago 34 percent of all street trees were green ash and 27 percent were silver maple. Sixty-one percent of street trees were limited to two species of trees As the threat from the emerald ash borer continues we need to be diligent and diversify our tree population so that when the ash borer arrives we will not see the affects to our tree population that we did with Dutch Elm disease. The City of Sioux City has been working to balance the tree species in the parks and city maintained areas by not planting ash trees or silver maples. Some of the trees being planted are widely known such as oaks, lindens and crabapples. The city also has been planting trees that are lesser known such as ginko, Kentucky coffeetree, redbud, whitepines and service berrys. In the future, beech and European hornbeam will be planted to further the diversification of the tree species. By taking these steps to balance the tree population, we can lessen the catastrophic loss of trees and avoid massive and expensive tree protection programs.
Homeowners should look at diversifying their trees as well. The reasons are the same as for city trees but homeowners can gain additional values. With a varied tree species on a property the aesthetics can increase, which in turn raises the property's value. In addition, with different species comes different shapes and sizes which can afford a home more protection from the elements. Trees can save a homeowner up to 15 percent on heating costs and up to 40 percent on cooling costs. This can be a considerable savings to a homeowner given the life of the tree and the initial investment in the tree. As we plan for the future we need to look at not only where we are planting trees and what we want them to look like, but what species we are planting. In doing this we will be providing a vital resource for generations to come.
For more information on a species that could be used to used to diversify the tree population contact the Parks Maintenance Department at 279-6886.