Global hotspots for soil nature conservation

Abstract

Soils are the foundation of all terrestrial ecosystems 1 . However, unlike for plants and animals, a global assessment of the hotspots for soil nature conservation is still lacking 2 . This hampers our ability to establish nature conservation priorities for the multiple dimensions supporting the soil system: from soil biodiversity to ecosystem services. Here, we conducted a global field survey including biodiversity (archaea, bacteria, fungi, protists, and invertebrates) and function (critical for six ecosystem services) observations within 615 composite topsoil samples from a standardized survey in all continents, to identify global hotspots for soil nature conservation.We found that each of the different soil ecological dimensions (i.e., soil species richness [alpha diversity, measured as ASVs], community dissimilarity, and ecosystem services) peaked in contrasting regions of the planet, and were associated with different environmental factors.Temperate ecosystems showed the highest species richness, while community dissimilarity peaked in the tropics, and colder high-latitudinal ecosystems were identified as hotspots of ecosystem services. These findings highlight the complexities of simultaneously protecting multiple soil ecological dimensions. We further show that most of these hotspots are not properly covered by protected areas (over 70%), and are vulnerable in the context of multiple global change scenarios. This first global estimation of soil nature conservation priorities, highlights the fundamental importance of accounting for the multidimensionality of soil biodiversity and ecosystem services to conserve soils for future generations. Main text:Soils are essential to support terrestrial life on the planet 1 . They are home to diverse assemblages of organisms across all major lineages of life from bacteria to invertebrates, and provide multiple ecosystem services such as soil fertility, carbon (C) storage, waste decomposition, pest control, and water retention 3-5 that are critical for food production and human well-being 6-8 . However, soils are also highly vulnerable to anthropogenic disturbances such as climate change 9,10 and land use intensification (e.g., land-use change, pollution, and erosion 11,12 ). For an adequate conservation of soils, it is critical to consider and protect the

Frontiers in soil ecology—Insights from the World Biodiversity Forum 2022

“…We identify a few key areas that may advance our fundamental understanding of soil biodiversity-ecosystem functioning links in the real world and allow for incorporating aspects of soil biodiversity in global climate and biogeochemical models. Moreover, this will allow us to develop predictive models for future changes in soil biodiversity (Delgado-Baquerizo et al, 2020a;Guerra et al, 2021b), ecosystem functioning (Delgado-Baquerizo et al, 2020a) and high-priority conservation areas (Guerra et al, 2022):…”

“…Considering multiple diversity metrics (e.g., alpha-, beta-and gammadiversity) is needed to develop a comprehensive understanding of how biodiversity is changing in the Anthropocene (Guerra et al, 2020(Guerra et al, , 2022McGill et al, 2015), as different biodiversity metrics may have different determinants across large spatiotemporal scales (Guerra et al, 2020;Potapov et al, 2022;Soudzilovskaia et al, 2015), or across environmental and disturbance gradients (Potapov et al, 2019a). For instance, integrating various metrics could be useful to understand the mechanisms behind community turnover, species loss and ecosystem functions Guerra et al, 2022).…”

“…Considering multiple diversity metrics (e.g., alpha-, beta-and gammadiversity) is needed to develop a comprehensive understanding of how biodiversity is changing in the Anthropocene (Guerra et al, 2020(Guerra et al, , 2022McGill et al, 2015), as different biodiversity metrics may have different determinants across large spatiotemporal scales (Guerra et al, 2020;Potapov et al, 2022;Soudzilovskaia et al, 2015), or across environmental and disturbance gradients (Potapov et al, 2019a). For instance, integrating various metrics could be useful to understand the mechanisms behind community turnover, species loss and ecosystem functions Guerra et al, 2022). Most soil biodiversity studies observed changes in abundance and alphadiversity, for example, the number of species of specific taxa, as an indicator of soil biodiversity change, while beta-diversity, that is, species turnover, remains an understudied biodiversity metric (Guerra et al, 2020(Guerra et al, , 2022, but see Thakur et al, 2017).…”

“…For instance, integrating various metrics could be useful to understand the mechanisms behind community turnover, species loss and ecosystem functions Guerra et al, 2022). Most soil biodiversity studies observed changes in abundance and alphadiversity, for example, the number of species of specific taxa, as an indicator of soil biodiversity change, while beta-diversity, that is, species turnover, remains an understudied biodiversity metric (Guerra et al, 2020(Guerra et al, , 2022, but see Thakur et al, 2017). The combined assessment of multiple biodiversity facets is critical to understand drivers and effects of biodiversity Potapov et al, 2022).…”

“…A recent study shows, for example, that the abundance of microbes may be a better indicator of some ecosystem functions, rather than their biodiversity . We consider it important to integrate abundance and beta-diversity into large-scale studies to identify endemicity and vulnerability of soil organisms to global change (Tedersoo et al, 2022b), and to evaluate the relevance of 'conserved' areas in protecting soil biodiversity (e.g., not only protecting highly diverse areas but also those ones with certain combinations of drivers and thus unique community composition and functioning; Guerra et al, 2022). Regarding the relationship between soil biodiversity and ecosystem functioning, it is largely unexplored which metric is more informative under different contexts.…”