Chaparral

Chaparral is widespread in California, where it is home to many endemic species. Its thick, leathery, evergreen shrub species are adapted to withstand drought and are dependent on fire to regenerate by crown-sprouting or seed germination. Despite its remarkable wildfire resilience, chaparral is threatened by increasing fire frequency as well as by historical fire management that disrupted its natural population cycles. Other threats include invasion by non-native invasive species, increasing drought frequency and intensity, urban development, nitrogen deposition, and fragmentation by roads and fuel breaks.

This assessment considered four metrics for chaparral health in the Ecological Health Assessment Study Area: minimum fire return interval, native shrub cover, native species richness, and low invasive grass cover. It found that chaparral in the Coastal Study Area was healthier overall than in the Central Study Area, likely due to longer fire return intervals and the higher relative cover of native shrubs. Native species richness and invasive grass cover were the same in both study areas, with a condition of caution and an unchanging trend. However, confidence in the quality of Coastal Study Area chaparral data is lower than for the Central Study Area due to its limited time span and small sample size.

Currently, more coastal chaparral transects are being included in annual monitoring efforts, so confidence in future health assessments should be higher. Other management and monitoring needs include coupling fire frequency data with the most up-to-date vegetation map to identify minimum fire return interval changes. To model vegetation response to reduced fire return intervals, this information could be paired with existing on-the-ground monitoring data. Restoration efforts (e.g., plant choice, seed sourcing) should consider “worst case” climate scenarios to determine focus on species better able to withstand highly variable weather conditions and resist increased fire frequency and non-native plant invasion.