Privately protected areas provide key opportunities for the regional persistence of large- and medium-sized mammals

Biodiversity conservation relies heavily on protected areas (PAs). However, in locations that are desirable for agriculture, industry, or human habitation (e.g., lowland habitats on fertile soils, coastal zones), land is often privately owned and state-owned PAs tend to be under-represented. Despite the potentially disproportionate contribution that privately protected areas (PPAs) could make to representing biodiversity and supporting its persistence across regional PA estates, this contribution is poorly understood. 

We assessed the capacity of PPAs to contribute to the persistence of 38 large- and medium-sized mammals in the Cape Floristic Region, South Africa, based on a previously published conservation plan that used species population requirements to identify areas of importance for mammal conservation. 

We hypothesized that, relative to state-owned PAs, PPAs would be disproportionately located in areas important to the regional persistence of the mammal assemblage, given: (a) historic biases in the distribution of private- and state-owned land across high and low productivity landscapes, respectively; (b) private landholders’ recent focus on wildlife-orientated enterprises; and (c) the conservation trade-offs influencing expansions of the state-owned PA estate. 

As a result of the high numbers of PPAs and their bias towards areas of importance for mammal conservation, the potential mammal species diversity and richness that could persist within a PA increased more rapidly with PA size on PPAs than on state-owned PAs. These PPAs therefore have the potential to significantly increase both the regional-scale diversity of protected mammals and the number of viable populations. Furthermore, PPAs could make the greatest absolute contribution to the conservation of protected species when adjoining, and thus expanding, state-owned PAs (i.e., mixed-ownership PAs). Regional conservation targets for a quarter of the species were only met due to the inclusion of private- and/or mixed-ownership PAs in the estate. 

Policy implications. Our findings show that privately protected areas (PPAs) could play a substantial role in the long-term conservation of terrestrial megafauna within a multi-tenure protected area (PA) estate, due to their prevalence in high-productivity landscapes. The significant gains from augmenting state-owned PAs with PPAs emphasize the value of systematic conservation planning and implementation across tenure types.