Effective land planning must balance the needs of people and the natural world [1
], particularly because land cover change and habitat loss are among the leading causes of biodiversity loss [2
]. Mammals are no exception to the global phenomena of range reduction and habitat loss [3
]. Mammals across a range of body sizes and trophic guilds change their behaviors in direct response to human-induced changes in land cover and increased human presence [4
]. Furthermore, there are apparent dichotomies in mammal responses to changes in the Anthropocene, with species such as omnivorous mesopredators, herbivores, and domesticated species exhibiting clear advantages over obligate carnivores, apex predators, and habitat specialists [6
]. For example, some species within carnivore guilds avoid urban areas, whereas others increase their abundances in these anthropogenic environments [10
Mammals are often difficult to detect even when present, but technological advances in non-invasive sampling (e.g., camera traps, genetic tagging, etc.) have helped accumulate global mammal diversity and distribution data [14
]. Despite the increasing availability of wildlife data, few studies have integrated these data to map the distributions of mammal species in regions undergoing expansive land changes [12
]. These projected species distribution models can then be used to predict range shifts in response to future landscape scenarios, such as those projected under climate change [17
]. Contemporary biodiversity data provide valuable snapshots of mammal distributions, but they have not been applied to projections of land cover change to forecast community distributions in the future. These predictions would be informative to stakeholders, as they coordinate and select planning policies to preserve biodiversity and their associated ecosystem services.
We projected changes in a suite of habitat-relevant land cover types for a rapidly changing landscape in northern Virginia under four different scenarios that varied in policy to plan development strategically (e.g., urban centralized) or reactively (e.g., sprawling) over the next 50 years, while accounting for differences in the rate of human population growth [19
]. Scenario planning is a strategic planning approach whereby alternate storylines or “scenarios” of the future are generated and their potential impacts are examined. Scenario planning is particularly useful in the conservation realm because of the high degree of uncertainty associated with future changes and the potential for significant impacts resulting from divergent policies [20
]. This study used scenarios that were developed with regional stakeholders’ inputs to increase their relevance to the projected future landscapes [19
We used wildlife detections, obtained through deployments of camera traps along a large-scale urban-to-wild gradient in northern Virginia, to create occupancy models to estimate land cover effects on those mammals detected. We predicted that species such as the American black bear (Ursus americanus) and bobcat (Lynx rufus) would respond negatively to human development and be most sensitive to habitat loss, because they are large omnivorous and obligate carnivores, respectively, which require substantial suitable habitats to persist. On the other hand, species such as urban-associated red foxes (Vulpes vulpes), free-roaming domestic cats (Felis catus), and generalist herbivores like white-tailed deer (Odocoileus virginianus) were predicted to respond positively to human-derived habitat fragmentation and land cover change, regardless of planning scenarios. The predictive models can inform planning commissions as to which scenario would be most effective to sustain mammalian assemblages.
We were able to model the predicted response of five representative mammal species to four planning scenarios for the study area. Although there was some variation in species-specific responses among the scenarios, we still presented unified patterns for use by land managers and development planners. Future landscapes would be beneficial and useful to both land managers and animal communities if they retained substantial habitat for sensitive species, and minimized expansion by the synanthropic species. Based on those criteria, it is not surprising that our results suggest that LS would be the most useful planning policy, with strategic planning for development and agriculture (and low population growth) retaining the most forest cover and the associated mammal communities.
Although bears and bobcats are sensitive to habitat loss and fragmentation [12
], our results suggest that future habitat loss in this region is relatively limited, regardless of the planning policies adopted. This result highlights the observation that bears and bobcats are already largely restricted to the two largest forested areas (Shenandoah NP and George Washington NF) and that these areas will not lose significant habitat-appropriate areas in future projections due to their protected status. Counter to our predictions, the β coefficients from the occupancy models suggested a negative but weak association between these species’ distribution and protected areas. However, the relationship reveals that, aside from these two large forested areas, most other protected areas remain small or isolated, particularly among private protected lands [30
], and their protected status alone is not enough to support these carnivores. In the case of bobcats, habitat losses are projected to be five times greater in unprotected areas under the high human growth scenarios. Bears exhibit less pronounced habitat losses in unprotected areas, likely due to their adaptability to living in exurban areas [39
]. These results highlight the importance of protected areas for biodiversity preservation in developing landscapes [40
], and their importance will only increase in the near future, as many small private forest patches are lost to development under each of the scenario models.
Both free-roaming domestic cats and red foxes are predicted to expand their distributions in the study area with the expansion of development and anthropogenic land uses under all scenarios. Those results correspond with other studies that show these mesopredators are highly associated with humans [7
]. The impacts of range expansion by both species could be detrimental to biodiversity (e.g., small mammals, songbirds, and herpetofauna), particularly if high densities of cats and foxes are sustained due to subsidies from humans [41
]. However, our predictive mesopredator models do not include interspecific interactions, which might further influence these predictions [43
]. Specifically, coyotes were fairly common in our study area and they are known to influence the site use, abundance and behavior of both domestic cats and foxes [10
]. Yet, our occupancy models did not have strong predictive power to accurately assess coyote distributions, and hence we were unable to directly incorporate these trophic interactions that might continue to limit the future expansion of mesopredators.
While our species are representative of relatively sensitive or synanthropic species, it is important to note that these five species and the additional 10 species detected are only a subset of historical mammal diversity from the study area. Apex predators (i.e., wolves (Canis lupus
) and mountain lions (Puma concolor
)) were extirpated, and other obligate carnivores, such as mustelids, are rare and were likely extirpated from much of the study area. Mesopredators have ascended to be the de facto
top predators in many anthropogenic landscapes, yet we are only now learning the roles of many of these medium-sized predators in the context of trait-mediated cascades and their effectiveness in regulating herbivores and lower trophic taxa [28
]. As such, our results are applicable for a typical eastern US landscape but might not represent the community dynamics of areas with intact apex predator guilds, such as the upper Midwest or Western US.
Our study was one of the first to pair contemporary camera trap data with occupancy models to predict current species distributions and then explore how those distributions might change under alternative planning scenarios in a rapidly developing area. However, we were unable to accurately predict the distributions of several mammalian species in contemporary times, and hence unable to predict potential changes in the future. Many of those species are common and highly associated with humans; e.g., northern raccoons and eastern gray squirrels. These synanthropes are likely responding to more fine-scale covariates, as exemplified by raccoons, most positively associated with housing densities and the associated human refuse, outdoor pet food, bird feeders, and other resource subsidies in anthropogenic and heterogeneous landscapes [47
]. These unmodeled species will likely interact with other taxa, and therefore, warrant further examination with higher resolution habitat and anthropogenic covariates. Furthermore, our land cover predictions and planning scenarios operated over a short time span and did not incorporate potential climate change. Indeed, contemporary studies have shown that small mammals and plant communities are stratified and shift along elevational gradients, with prey responding variably to these synchronous plant community shifts in response to climate change [50
]. However, since we cannot account for these changes in medium and large mammals or our land cover predictions, we do not expect these changes to affect medium and large mammals strongly beyond the scope of our predicted models, although we might consider our models conservative with respect to climate uncertainty.