Evaluating the impacts of recreation on connectivity across an ecological network
The central principle of ecological networks designed to conserve biodiversity is that viable populations and natural communities can be supported by a connected landscape network. Although the direct effects of habitat loss and fragmentation the most imminent threats to these networks, human activities, such as recreation within habitat cores and linkages comprising the ecological network, may affect functional connectivity for some species and could present a risk to the functioning and viability of a network. To assess the status of connectivity and impacts of recreational activity in a landscape-scale conservation network in southern California, we collected occupancy and habitat use data on a range of medium to large vertebrate focal species using remote cameras. Over 300,000 images were logged from 36 camera stations, and we identified the species and number of individuals in each photo. We analyzed all camera data using generalized linear models (GLMs) followed by an occupancy modeling approach to identify the relationship between different recreation activities (humans, bikes, motor vehicles, and domestic dogs) and wildlife species richness, relative abundance, activity patterns, and occupancy within habitat cores and linkages.
Humans were detected at 34 of 36 camera stations, and foot traffic was by far the most common type of recreation. We found that richness of nine focal species was highest at moderate levels of recreation while relative abundance was variable. Coyote and mule deer relative abundance was highest at low and high levels of recreation while highest for bobcat, gray fox, puma, and roadrunner at low to moderate levels. At stations with the highest human activity, species that may be active during the day but are generally crepuscular or nocturnal were detected less often in the daytime compared to lower recreation sites. Finally, detection of our focal species appeared to be most closely tied to whether a station was in core habitat or a linkage. Detection of most species was lower in linkages than in cores, regardless of recreation activities. Overall, while recreation did appear to affect relative abundance and activity patterns of some species, underlying habitat quality is likely the most important feature driving species occupancy and activity patterns. While this suggests that human activity may not deter species from utilizing core habitats, it may affect connectivity for species that rely on linkages to move through the network.