Establishing protected areas is a key way to conserve biodiversity. When numerous protected areas are created to form an extended network, they can enhance connectivity and protect a wide range of species and biomes.
Global strategies like Aichi Biodiversity Target 11 and the 30×30 initiative have created concrete conservation targets that can be achieved through the creation of protected area networks. However, converting the idea of protected areas into a concrete plan is a challenge, especially on a large-scale.
Tjaden-McClement, K., Naidoo, R., Brennan, A. and Burton, A.C. 2025. Global prioritization schemes vary in their impact on the placement of protected areas. PloS one 20(1): e0307730.
Officially designating a protected area requires extensive planning and collaboration from multiple groups of stakeholders, all of which may have differing priorities for which areas should be protected and in what order they should be designated. While there have been numerous optimization schemes suggested for prioritizing the creation of protected areas, deciding which scheme is most effective for achieving targeted goals in time remains difficult.
A new comparison of two high-profile prioritization schemes helps shed light on which might be more effective, particularly for increasing the rate of protected area growth. The first is Biodiversity Hotspots, developed by Conservation International, which is a reactive scheme that prioritizes areas based on high levels of both irreplaceability and threat. The second is Last of the Wild, a proactive scheme that aims to protect the world’s most pristine wilderness areas by delineating large contiguous areas of the “wildest” areas in each biome in each realm. The comparison consisted of a Before-After Control-Impact causal analysis of time-series trends in protection to test whether the implementation of either scheme positively influenced the rate of creation of protected areas in priority vs. non-priority areas.
The results show that when the Last of the Wild prioritization scheme was established, the rate of protection in its priority areas increased compared to non-priority areas. The same was not true for Biodiversity Hotpots, where there was no increased rate of protected areas after establishment. This difference is likely rooted in the basic ideology of each scheme: Biodiversity Hotspots aims to protect areas with high habitat loss and therefore high human pressure, giving them a high cost of implementation, whereas Last of the Wild focuses on areas with low human footprints, making them easier to protect.
This highlights the key differences tween using proactive versus reactive schemes, and how schemes that aim to protect areas with high human value are inherently more challenging to implement. Given this challenge, it’s possible that schemes trying to protect already threatened areas may not create protected areas at a rate fast enough to reach conservation targets.
While there are other priorities to consider beyond how quickly priority areas can be designated as protected, this rate is important to consider if timely targets are to be met. Achieving large-scale protection of critical land- and seascapes is necessary to ensure species remain protected and connected in a rapidly changing future.
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