A meta-analysis of recreation effects on vertebrate species richness and abundance

Most protected areas globally have a dual mission to conserve natural resources and provide access for outdoor recreation or ecotourism, yet questions remain about the ecological effects of recreation. We conducted a global meta-analysis of the effects of recreation on vertebrate richness and abundance. We estimated that vertebrate richness (n = 15 articles) and abundance (n = 32) are lower in association with higher levels of recreation in over two-thirds (70%) of cases. We observed a moderate negative group-level effect of recreation on bird and mammal abundance, but the group-level effect on fish and reptiles was not significant. Effects were stronger for carnivores and herbivores than for omnivores, and stronger for small-bodied birds and ground-nesting birds than larger and tree- and shrub-nesting birds. Terrestrial activities were associated with reduced vertebrate abundance, whereas aquatic activities were not. Both motorized and nonmotorized activities were associated with reduced vertebrate abundance, but the effect for motorized activities was uncertain due to small sample size. These results pose a challenge to natural resource management agencies who must balance recreation access with natural resource protection, and to conservation organizations that rely on outdoor recreation for public support and funding. We recommend that managers plan recreational access at a regional scale and include some areas that are closed to recreation to minimize trade-offs between recreation and animal conservation.