There has been a declining population of Mission blue butterflies at the nearly contiguous Twin Peaks Natural Area; while park employees logged about 150 butterflies in the 1980s, only four were found between 2001 and 2007. A reintroduction was done in April 2009. Reintroduction may also be possible in Glen Canyon Park. Here the main issue appears to be re-establishing the native plant "silver bush lupine", whose leaves are the larval food of these butterflies. A substantial fraction of Glen Canyon Park is now covered by non-native species including eucalyptus forest (17 acres), French broom (6 acres), and field mustard, but no specific proposal for re-introduction of the lupine was included in the Management Plan.