There is growing recognition of the need to monitor additional species of local or regional conservation concern. These may include regionally rare species and endemics that are not sufficiently threatened for federal listing, and species that are listed at the state or local level. Oftentimes, rare species are found within unique or atypical natural habitats that support unusual species assemblages. Identifying and monitoring these unique habitats and their associated flora is an important step toward meeting Park Service objectives of preserving and protecting natural resources. Knowledge of the distribution of rare plant populations with park areas helps to inform managers when considering land use and management alternatives.

Typically, rare plants occur in small populations often disjunct or peripheral to a broader distribution. Small populations have a greater probability of extinction due to random stochastic events (e.g. rockslide) or catastrophic demographic events (e.g. failure to set seed). Fragmentation of natural landscapes further isolates small, rare plant populations and degrades the inter-population matrix for dispersal. Isolation reduces the probability of colonization and upsets the balance between local extinction and re-colonization. Many rare plant populations are disjunct or peripheral to larger populations and grow in conditions nearing their ecological limits. The persistence of these populations may be especially susceptible to global climate change.

Monitoring questions and approach

1. Which rare species occur in the park and where are they located?

   • Research herbarium collections and state natural heritage records. Identify and map rare plant populations with GPS.

2. Are populations of rare plants persisting over time?

   • Periodically revisit known populations and search for new populations.

3. Is the size of rare plant populations changing over time?

   • For high priority species, measure abundance through complete census or sample.

Protocol

• DeBacker, M.D., L.P. Thomas and J.R. Boetsch. In preparation. A practical framework for monitoring rare plant species. Prairie Cluster Prototype LTEM Program, National Park Service, Republic, MO.