Illinois Updates Conservation Status Ranks of Threatened and Endangered Plants

Scientists from the Illinois Natural History Survey and the Illinois Department of Natural Resources have updated the state conservation status ranks, or S-ranks, of threatened and endangered plants in Illinois. The update includes some plants not recorded in the state for decades and finds many that, while still threatened, are doing better than previously thought. The 331 plants on the list are as fascinating as they are rare, with species like carnivorous plants, orchids, and a native version of wild tarragon persisting in the wild despite small populations.

Key Takeaways:

• The updated S-ranks include 331 plants, with 257 species listed both in 1987 and 2023, but their rankings improved, with a decrease in the number of the most imperiled species from 228 to 152.
• Only three species were found to be more imperiled than in 1987, while eight of the state-listed plants are also listed as threatened or endangered at the federal level.
• The regions with the highest concentration of threatened and endangered plant species include northeast Illinois, central Illinois, and floodplains along the Illinois and Mississippi River Valleys.
• The team used an established protocol for ranking each species based on its rarity, threats, and population trends, and gathered data from the Biotics database, online sources, regional conservation districts, and field research.
• The update provides a new perspective on the status of rare plants in Illinois, with some species found to be doing better than previously thought, while others are still not doing well at the individual population level.
• Citizen efforts can make a big difference in protecting rare species, and interested Illinoisans are encouraged to volunteer with Friends of Illinois Nature Preserves or Plants of Concern.
• The project was supported by the Illinois Department of Transportation and was made possible by the regional, national, and international expertise of the botanical team at INHS.

Statistics:

• 331 plants on the updated S-ranks list
• 257 species listed both in 1987 and 2023, with improved rankings
• 152 species with the most imperiled ranks in 2023 (down from 228 in 1987)
• 8 state-listed plants also listed as threatened or endangered at the federal level
• 3 species found to be more imperiled than in 1987
• 8 regions with high concentration of threatened and endangered plant species in northeast Illinois, central Illinois, and floodplains along the Illinois and Mississippi River Valleys
• 150+ populations of rare species found in areas where they had been reported historically
• 331 species included in the update, with some species not recorded in the state for decades

Sources:

• Illinois Natural History Survey
• Illinois Department of Natural Resources
• Natural Areas Journal
• NatureServe Network
• Consortium of Midwest Herbaria
• iNaturalist
• Global Biodiversity Information Facility
• Friends of Illinois Nature Preserves
• Plants of Concern
• Illinois Department of Transportation
• DOI: 10.3375/2162-4399-45.3.5