Land tenure contributions to protected area growth under alternative conservation targets in the Australian monsoon tropics

As the global protected area (PA) network expands to meet international targets, it is important to assess whether traditional reliance on public land will suffice for projected PA growth or whether other tenures, such as Indigenous or pastoral lands, may increasingly contribute. Another consideration is whether the relative importance of different tenures varies depending on the specific goals of the PA network. We used the mammal fauna of the Australian monsoon tropics (AMT), one of the world's largest intact tropical savannas, as a case study to address these questions. We applied systematic conservation planning to identify optimal PA configurations under 2 objectives (adding to the existing PA network from any tenure vs. expanding the Indigenous protected area [IPA] network through voluntary declaration of Indigenous lands by traditional owners) and 2 species protection criteria (prioritizing currently threatened species vs. species predicted to become threatened). We calculated planning unit selection frequencies for the resulting 4 scenarios to identify high-priority areas for mammal conservation and assessed their dependence on different tenure categories. All scenarios relied heavily on Indigenous lands to achieve species representation targets, with varying contributions from pastoral land depending on the criteria prioritized. Protecting potentially threatened species required more pastoral land and Indigenous land coexisting with primary industries, whereas targets for currently threatened species were more cost-effectively met through voluntary declarations of Indigenous freehold land as IPAs. Our results highlight the potential for Indigenous lands to play a major role in achieving biodiversity conservation targets and demonstrate that land tenure requirements vary depending on conservation priorities. These findings emphasize the need to explicitly consider tenure in conservation planning to guide collaborative strategies and ensure PA growth aligns with specific biodiversity goals across diverse land management contexts.