Minneapolis Street Tree Planting Guidelines to Increase Diversity

Abstract The threat and eventual loss of ash trees ( Fraxinus ) to emerald ash borer ( Agrilus planipennis ) in Minneapolis, MN, USA, was a major opportunity to establish a more diverse and resilient public street tree population. This generational opportunity was embraced. With the goal of increasing urban forest resiliency against future pests and conditions, Minneapolis developed and applied multiscaled tree selection guidelines to systematically select and plant a diverse mix of trees. Within a relatively short amount of urban forest time, the diversity of the Minneapolis public street tree population greatly increased. Within the past two decades, the number of genera that make up 1% or more of the public street tree population has nearly doubled. Before the guidelines, maple ( Acer ) comprised 30% of the public street tree population. Currently, there are no genera that comprise 20% or more of the public street tree population in Minneapolis. As a result of the guidelines, there is more diversity across the whole city, within neighborhoods, and along individual street block segments. The benefits of this diversification will hopefully lessen the exposure to and impact of future urban forest pests and other challenging conditions.