Plant biodiversity is declining across Indiana. As of 2020, 44 Indiana native plant species are no longer found in the state, an additional 246 are endangered (at risk of extinction) and 192 are threatened (on the brink of becoming endangered) at the state level. Much of this species loss is due to habitat destruction, but climate change and invasive species also threaten native plants.
While native plant species have been declining, many non-native plants (plants that were not historically found in Indiana but arrived from elsewhere) have colonized the Hoosier state. Many of these species do not cause economic or ecological problems, but many others do by outcompeting Indiana's native plants and transforming our forests and prairies. For example, garlic mustard invades forests where it uses chemical warfare to attack the fungal mutualists (mycorrhizae) that funnel nutrients to many of our charismatic spring ephemeral native plant species. As a result, in forests invaded by garlic mustard, native plant diversity is quite low, and many native species may take years to recover even after garlic mustard removal because of long-lasting effects on the mycorrhizae.
When the threat of climate change is added to the mix of habitat loss and invasive species, natives appear to be facing an uphill battle. One way that plants respond to climate change is by advancing their phenologies, or timing of life history events, to germinate or begin to grow earlier in the spring and flower earlier.
Ultimately, whether a plant wins or loses in the face of climate change may be determined by its ability to shift its flowering times to match warmer conditions. We know from long-term surveys that plant species that manage to flower earlier in warmer years survive or even increase in abundance; species that cannot have declined over the past century.
Unfortunately, recent work suggests that native prairie species like those found in Northern Indiana are not very good at advancing their phenologies. Instead, problematic invaders are the ones capable of substantially advancing their flowering times in response to warming. Thus, climate change may hinder native species both because they are less capable of responding to climate change and because one of their other major threats, invasive species, are good at responding to climate change.
Given the myriad threats facing Indiana native plant species, how can we shift the balance back to native species? One answer is restoration. For example, prairie habitat has been decimated across the United States, so that prairie habitats are now considered North America's most endangered ecosystem. However, a number of successful restorations in the northern part of the state are taking land that was previously used for agriculture and restoring this habitat that is home to charismatic native species like the 6–12- foot-tall Compass Plant and the Wild Blue Lupine, the only known host to the endangered Kerner blue butterfly. Similar restorations on a small scale can be seen across the state from city parks to backyard monarch way stations.
One challenge that these restorations face, however, is how to restore these native species in the face of current and future climate change. For restorations, local seed is typically preferred. In the past, this certainly made sense given that seed collected from nearby habitats should be more likely to be adapted to local climate conditions and potentially even to local soil types. One big question is whether this still makes sense. Given that climate is changing so rapidly, do we need to change our restoration strategies to either include more southern populations or genetically diverse mixes that can facilitate adaptation to the novel environments our restored plant communities will face? Biologists at the Midwest Center for Biodiversity are investigating this question.
