Utilizing a top predator to prioritize site protection for biodiversity conservation.

Ongoing global change makes it ever more urgent to find creative solutions for biodiversity preservation, but prioritizing sites for protection can be challenging. One shortcut lies in mapping the habitat requirements of well-established biodiversity indicators, such as top predators, to identify high-biodiversity sites. Here, we planned site protection for biodiversity conservation by developing a multi-scale species distribution model (SDM) for the raptorial Northern Goshawk (Accipiter gentilis; goshawk) breeding in an extensive megacity region of Japan. Specifically, we: (1) examined the determinants of top predator occurrence and thus of high-biodiversity value in this megacity setting, (2) identified the biodiversity hotspots, (3) validated whether they actually held higher biodiversity through an independent dataset, and (4) evaluated their current protection by environmental laws. The SDM revealed that goshawks preferred secluded sites far from roads, with abundant forest within a 100 m radius and extensive forest ecotones suitable for hunting within a 900 m radius. This multi-scale landscape configuration was independently confirmed to hold higher biodiversity, yet covered only 3.2% of the study area, with only 44.0% of these sites legally protected. Thus, a rapid biodiversity assessment mediated by a top predator quickly highlighted: (1) the poor development of biodiversity-friendly urban planning in this megacity complex, an aspect overlooked for decades of rapid urban sprawl, and (2) the extreme urgency of extending legal protection to the sites missed by the current protected area network. Exigent biodiversity indicators, such as top predators, could be employed in the early or late stages of anthropogenic impacts in order to proactively incorporate biodiversity protection into planning or flag key biodiversity relics. Our results confirm and validate the applied reliability of top predatory species as biodiversity conservation tools.

Top predators as biodiversity indicators: A meta-analysis.

Identifying efficient biodiversity indicators is a key pillar of the global conservation strategy. Top predators have been proposed as reliable biodiversity signposts, but their role is controversial. Here, we verified their performance by a meta-analysis of published studies and found solid support for their efficacy as biodiversity indicators. As to be expected for any indicator species, efficacy was stronger for biodiversity components 'ecologically closer' to the predator (i.e. broad groups that include species providing key resources, such as avian and tree diversity for a bird-eating predator that nests in trees) and declined for the diversity of components more 'ecologically remote' from the predator (e.g. butterfly diversity for a fish-eating predator). This confirmed a link between the top predatory role and biodiversity and set the context for its functionality. These results show that, on average, top predators are justified candidates as biodiversity indicators and that prioritisation of conservation action based on their occurrence is likely to provide broader ecosystem benefits. However, such role should be confirmed on a case-by-case basis, acknowledging that no indicator can portray everything, checking the compatibility of the biodiversity components linked to the predator with the established conservation objectives and ideally integrating predators with other complementary indicator groups.

Raptor breeding sites indicate high plant biodiversity in urban ecosystems.

Preserving biodiversity in urban ecosystems has become an urgent conservation priority, given the rapid upsurge in global urbanization. As woody plants play essential ecological roles and provide psychological benefits to human city dwellers, their preservation is of particular interest to conservation scientists. However, considering that extensive censuses of woody plants are resource-intensive, a key accomplishment is to find reliable conservation proxies that can be quickly used to locate biologically diverse areas. Here, we test the idea that sites occupied by apex predators can indicate high overall biodiversity, including high diversity of woody plants. To this end, we surveyed woody plant species within 500 m of Northern Goshawk (Accipiter gentilis) breeding sites in urban ecosystems of Japan and compared them with non-breeding control sites without goshawks. We found that goshawks successfully identified and signposted high levels of richness, abundance, and diversity of woody plants. Our findings show that sites occupied by top predatory species could be exploited as conservation proxies for high plant diversity. Due to their exigent ecological requirements, we would expect apex predators to be tied to high biodiversity levels in many other urban ecosystems worldwide.