Influence of disturbance on the connectivity of riparian forest habitat for terrestrial vertebrates

Natural and anthropogenic disturbance can influence the connectivity of riparian forest ecosystems affecting the movement of terrestrial vertebrates. We examined changes in connectivity of riparian forest habitat for terrestrial vertebrates following natural and anthropogenic disturbance between 2000 and 2021. We quantified changes in patch aggregation and used a circuit-theory model (Omniscape) to quantify changes in connectivity of riparian forest habitat within three hypothetical search distances representing the movement capabilities of terrestrial vertebrates (0–500, 0–1000, 0–2000 m). We replicated the analysis for six (> 10,000 km2) landscapes (i.e., provincial ecosections) in British Columbia, Canada. We used random forest regression to quantify hypothesized relationships between change in habitat connectivity and explanatory variables known to influence disturbance: topography, types of aquatic features (streams, lakes and wetlands), and management regime (industrial forest or protected area). Loss of forest across landscapes ranged from 3.1% to 12.3%. Changes in forest aggregation were consistent with clustered patterns of disturbances such as wildfire and large-scale outbreaks of bark beetles. Topography (elevation, slope, aspect) influenced changes in connectivity of riparian forest habitat. Loss of connectivity was greatest around small streams (< 5 m wide) within the finest search distance (500 m). The maintenance of forest immediately adjacent to water features, and in particular small streams, is important for ensuring the connectivity of riparian forest habitat for terrestrial vertebrates.