Diversity is the Spice of Life, Even in Natural Areas!

By: Gillian Field, originally published in the Herald Times on April 16, 2022

Indiana deciduous forests are some of the most diverse forests on our planet. They are made up of broad-leaved upper story trees, understory shrubs, wildflowers and unique wildlife. Autumn Brunelle, the Naturalist with Monroe County Parks and Recreation, helps to illuminate forest-diversity when she explains “something as simple as tree height can make a huge difference in the health of a forest.”

She further clarifies that “by focusing in and observing one small part of a forest, such as differences in tree height, we begin to see the complex interconnectedness within forest systems. In terms of forest strength and survival, all elements of the eco-system serve a purpose, whether that’s tree age, how trees are used by wildlife, or the fungi that is so important to forest regeneration.” In her example of tree height, Autumn notes “that when we focus in on the tallest trees in the forest, you’ll see that these tall trees provide shade for understory plants, create a taller vantage point to help birds of prey hunt better, and you’ll even see how they are able to protect younger or smaller trees from storm and wind damage. Ultimately, a diverse forest also has a higher chance of surviving disease and pests, and it provides countless food and shelter options for wildlife.”

Hoosier forests, as with all native habitat, have an intricacy that has evolved over millions of years. Nevertheless, a forest’s biodiversity and ability to regenerate is under threat by the recent introduction of non-native species. These are species, from other continents, that have not evolved with our plant species, soil biota, fungi, insect, bird and other wildlife populations. As Autumn Brunelle describes, “not all species are interested in living together.”

Callery pear taking over forests, photo courtesy of Indiana Native Plant Society

A specific example of a species that is not a welcome addition to the Hoosier forest family is Callery pear and all of its marketed cultivars. Autumn defines them as “an early bloomer and a quick grower.” Without insect and mammal herbivores to keep their growth in check, and without the intricate services native plant species offer that might offset their infestation, “Callery pears are great at creating ‘Callery Pear ONLY’ zones.”

Autumn describes a “Callery Pear ONLY” zone:  “Though beautiful while flowering, having an area made up of one species, that will grow to be the same size and height, with shared weaknesses, and with limited environmental benefits, will only result in a weak, disease prone, minimal wildlife zone.”

Callery pear flowers and leaves, photo courtesy of MC-IRIS

The consequence of allowing Callery pear to continue to grow and spread long distances from their urban landscape plantings has impacted our forests and wetland diversity. You can make a positive difference to counter this harmful trend by recognizing invasive Callery pear growing on your property and replacing them with native trees. Replace it with small, medium and tall native trees. Visit Monroe County Identify and Reduce Invasive Species website for information on Callery pear replacement tree species: Serviceberry (Amelanchier laevis and A. arborea), redbud (Cercis canadensis), American hornbeam (Carpinus caroliniana), hop hornbeam (Ostrya virginiana), pagoda dogwood (Cornus alternifolia).

Due to spreading infestations, Callery Pear is no longer planted by the City of Bloomington, and it is disallowed in new developments by the City's Unified Development Ordinance. Erin Hatch, Urban Forester with the City of Bloomington, is the best person to contact to remove Callery pear located in sidewalk green strips and other right-of-way areas. These are considered city trees. Erin notes, “If adjacent property owners wish to conduct tree work, such as removal of these trees, at their own cost, they can submit a tree work permit application.” Visit here for more information: https://bloomington.in.gov/about/trees.

Gillian Field is a member of MC-IRIS, also known as Monroe County — Identify and Reduce Invasive Species, a coalition of citizens aimed at reducing the environmental and economic impact of invasive plant species in the county.