Fiscal Note
Current estimates indicate that the population of Madison's terrace (between street and sidewalk) ash trees stands at approximately 21,700, representing over 24% of total terrace trees. Many thousands of ash trees also live in parks and greenways and on private property. The Emerald Ash Borer (EAB) has not yet been detected in Dane County, but was recently discovered in Janesville, approximately 28 air miles away. Although the insect spreads at a rate of only 0.5 to 0.6 miles per year under natural conditions, the infestation has made irregular and unpredictable leaps via the transmission of infested wood and nursery stock. Several months ago, the nearest known infestation was at Rock Cut State Park in Illinois, slightly more than 60 miles away.
When the EAB arrives, insect populations will initially build very slowly, but will later increase rapidly as the number of infested trees grows. At peak infestation levels, many trees will decline and die within one or two years. The infestation would eventually prove fatal to all City ash trees, as no North American ash trees have any natural resistance.
The EAB can be expected to cause significant economic difficulties for the City of Madison. Costs for removing and replacing the entire terrace ash tree population are estimated at $13,100,000, incurred over a period of years. Alternatively, chemical treatments of the terrace ash population are an option. However, it is estimated that these treatments would carry an annual cost of over $437,000 for many years. As the ash population gradually expires, treatment costs would slowly drop and eventually disappear entirely. However, terrace ash trees can be expected to live from 30 to 40 years, and the planting of such trees was only discontinued in 2006. Although the total number of ash trees would slowly fall over time due to natural attrition, smaller trees at the same time become larger and consequently more expensive to treat. As the current ...
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