Glen Canyon Park used to support populations of two rare species: the "vulnerable" San Francisco forktailed damselfly and the "endangered" Mission blue butterfly. The plan proposes changes in the management of the park that would promote self-sustaining populations of these insects. The damselfly population in the park was studied by John Hafernik and his colleagues in the 1980s prior to its local extinction; they re-introduced a population of these damselflies in 1996 that persisted for two seasons. The damselflies need open water habitat, which has proven difficult to maintain.