Planting for the Future

The climate is changing. Wisconsin continues to warm and receive more high-volume precipitation events,  trends that are projected to continue through the 21st century.  These changes are exacerbated in urban areas, places that are already warmer than the surrounding region due to the way asphalt and other manmade surfaces capture and reradiate heat.

Urban forests are powerful tools to help meet some of the climate-borne challenges we face in our communities, from excessive heat to flooding to air pollution. But in order to deliver the incredible number of benefits that trees can provide, they need to survive and thrive. Current trees need care and attention (consider reaching out to a  local certified arborist ), while future plantings will be more successful if current and future climate changes are kept in mind. Urban foresters always have the “right tree, right place” mantra at the forefront of their thoughts, but what is the right tree and the right place in an uncertain climate? This story map aims to shed some light on that question.

This Wisconsin DNR Planting for the Future application is broken down into three different sections. The first shows potential changes in the state’s cold hardiness and heat zones, key determinants of what trees can grow where. The second section highlights a dozen tree species that have promising futures under different climate scenarios. Some Wisconsin communities are already planting those species and they are featured in the third section. 

What the Wisconsin climate is like in 50 or 100 years is very much up to the global community. Do emissions continue the same trajectory as the last century? Do we take full advantage of the carbon storage or greenhouse gas reduction capacities of forests, grasslands and wetlands (called  Natural Climate Solutions )? Whatever the future holds, Wisconsin is most likely to continue experiencing warmer temperatures, with bigger increases in the northern parts of the state.

The below maps show current and modeled cold hardiness zones in the state, which represent the average minimum temperature a location is expected to experience. The current map has been simplified for comparison to the future models by eliminating zone subdivisions (e.g., 4a becomes 4 and 5b becomes 5).

Learn more about different hardiness zone maps in  Forestry News , and explore modeled changes for the entire country in the  story map  from the U.S. Forest Service.

Though not causing the immediate harm possible from low temperatures, heat can cause long term damage to plants, particularly if not paired with additional summer precipitation. Heat zones are mapped by days per year over 86 degrees Fahrenheit and can show potential heat stress for plants and animals.

The map below shows the current heat zones in Wisconsin. Swipe left on the arrow to show the projected heat zones at the end of the century, if current emission trends continue. Open the legend in the map's lower left corner.

Not all trees are created equal, nor do they all thrive in similar conditions. Anticipated temperature increases could add stress to already stressful urban environments, jeopardizing a species' long-term use in communities. Conversely, the new conditions  could introduce additional species to your area , intentionally or not. While it’s too simplistic to assume species common in the north face a perilous future, species with southern ranges will generally find more appealing grounds in the state’s urban areas. However, suitable species also need to be adaptable to the harsh urban landscape.

Click on the names in the caption to find out more about each species from the Morton Arboretum.

There are  guidelines to maintaining species diversity  in the urban forest and, on a state-wide scale, none of the trees identified above is overplanted, though some are more common than others. Eastern redbud and Turkish hazelnut, for example, can be found in dozens of communities across Wisconsin. Chestnut oak, on the other hand, is grown by few communities, according to the  Wisconsin Community Tree Map , a compilation of tree inventories from around the state.

The climate scenarios and climate-tolerant species highlighted in this story map are modeled. That is, they offer projections for what is possible based on existing evidence. The list of species does not show all the trees that can thrive in future climate scenarios, but merely notes a small group that have been more carefully investigated. Furthermore, urban areas have many microclimates that may permit different species in different parts of town. For example, the area immediately around your house may be slightly warmer than your open yard.

The key in all things urban forestry is diversity. As a  species diversity guide for homeowners  notes, “By planting smaller quantities of many different species, we create a more resilient urban forest less affected by any single threat.” And with our warming climate, this is as good of a time as any to experiment with some trees that might not have been appropriate when you were growing up.