Towards evidence-based conservation of subterranean ecosystems

Subterranean ecosystems are among the most widespread environments on Earth, yet we still have poor knowledge of their biodiversity. To raise awareness of subterranean ecosystems, the essential services they provide, and their unique conservation challenges, 2021 and 2022 were designated International Years of Caves and Karst. As these ecosystems have traditionally been overlooked in global conservation agendas and multilateral agreements, a quantitative assessment of solution-based approaches to safeguard subterranean biota and associated habitats is timely. This assessment allows researchers and practitioners to understand the progress made and research needs in subterranean ecology and management. We conducted a systematic review of peer-reviewed and grey literature focused on subterranean ecosystems globally (terrestrial, freshwater, and saltwater systems), to quantify the available evidence-base for the effectiveness of conservation interventions. We selected 708 publications from the years 1964 to 2021 that discussed, recommended, or implemented 1,954 conservation interventions in subterranean ecosystems. We noted a steep increase in the number of studies from the 2000s while, surprisingly, the proportion of studies quantifying the impact of conservation interventions has steadily and significantly decreased in recent years. The effectiveness of 31% of conservation interventions has been tested statistically. We further highlight that 64% of the reported research occurred in the Palearctic and Nearctic biogeographic regions. Assessments of the effectiveness of conservation interventions were heavily biased towards indirect measures (monitoring and risk assessment), a limited sample of organisms (mostly arthropods and bats), and more accessible systems (terrestrial caves). Our results indicate that most conservation science in the field of subterranean biology does not apply a rigorous quantitative approach, resulting in sparse evidence for the effectiveness of interventions. This raises the important question of how to make conservation efforts more feasible to implement, cost-effective, and long-lasting. Although there is no single remedy, we propose a suite of potential solutions to focus our efforts better towards increasing statistical testing and stress the importance of standardising study reporting to facilitate meta-analytical exercises. We also provide a database summarising the available literature, which will help to build quantitative knowledge about interventions likely to yield the greatest impacts depending upon the subterranean species and habitats of interest. We view this as a starting point to shift away from the widespread tendency of recommending conservation interventions based on anecdotal and expert-based information rather than scientific evidence, without quantitatively testing their effectiveness.Peer reviewe

IUCN red-listing of subterranean invertebrates: problems, gaps and the future

Red-listing is a widely used approach to globally evaluate the threats that affect a species, according to a set of standardized criteria. The IUCN Red List of Threatened Species is the world's most comprehensive inventory of the global conservation status of species. It is an international reference in this field, and a powerful tool for conservation of endangered species, sites and habitats.A number of subterranean organisms of various taxonomical groups have been assessed from a few decades, and are currently being assessed, revealing serious difficulties and uncertainties linked to the special characteristics of subterranean ecosystems and species. The most critical problems, that are linked to distribution, dispersion, life cycle and sensitivity to disturbance, and some ways to overcome them, are discussed in this paper.Partly linked to this, redlisting of subterranean species has so far achieved moderate results with regard to the diversity and vulnerability of subterranean species - with the well-known exception of bats. Data drawn from IUCN online database of redlsted species reveals that subterranean invertebrates are hugely under-covered at geographical and taxonomic levels. Moreover, among red-listed species that are connected to subterranean habitats, most are stygophiles and troglophiles, i.e. not obligate cave dwellers. In contrast, very few of the species strictly linked to subterranean life (stygobionts and troglobionts) have been red-listed so far, in spite of the exceptional proneness to endemicity of subterranean invertebrate groups.On an other hand, assessments are extremely uneven across countries and across taxa. Many regions with significant cave fauna do not have any assessed subterranean species. The richest countries in subterranean diversity are not those which have the highest number of assessed species. The zoological invertebrate groups that dominate cave fauna in diversity (beetles, springtails, microcrustacea...) have contrasted proportion of redlisted species: higher for snails, very low for microcrustaceans, beetles and springtails, with rare local exceptions.Assessment difficulties underlined above, low coverage of cave fauna in available assessments, limited progress in number of red-listed species in the face of the high number of concerned species, and the limited human resources to do the job led us to favour a more pragmatic approach to subterranean invertebrates red-listing for the coming years. Really threatened subterranean species are actually not numerous, because subterranean habitats are protected from most critical disturbance that devastate so many surface habitats. The aim will be therefore to focus on the most threatened species and sites in the world, with a particular attention on mining, water pollution and large scale surface habitats destruction

The IUCN-SSC Cave Invertebrate Specialist Group

The Cave Invertebrate Specialist Group, an IUCN Species Survival Commission, is a group of 80 taxonomists, biospeleologists, ecologists, and conservation biologists. Since 2014, our objectives have been to: (1) conserve subterranean habitats, and address one of the largest lacunas in conservation biology – the protection of sensitive cave and subterranean invertebrate populations; (2) conduct IUCN Red List evaluations for imperiled and/or narrow range endemic species; (3) encourage comprehensive baseline biodiversity surveys, in particular to determine the proportion of unknown biodiversity yet to be discovered; and, (4) provide collaborative opportunities with the business sector for conducting Environmental and Social Impact Assessments, Biodiversity Action Plans, and site and species management plans. We will our accomplishments over the past four years including growth of membership, the number of Red List evaluations conducted and the total number of species recognized as a conservation priority