The vertical dimension of conservation: A cost-effective plan to incorporate subterranean ecosystems in post-2020 biodiversity and climate change agendas

Subterranean ecosystems harbor a broad diversity of poorly-understood specialized organisms that are of interest from both a conservation and evolutionary perspective.

These species are often phylogenetically highly distinct, yet small-range endemics, and some represent ancient faunas that have disappeared from above surface habitats.

Thus, they account for a unique fraction of the global taxonomic, phylogenetic, and functional diversity that is currently imperiled by human activities, including the destruction of their subterranean habitats, pollution, and climate change1,2.

Furthermore, subterranean ecosystems and landscapes deliver critical nature’s contributions to people1,3, including an array of cultural values such as recreation (caving), tourism, education, aesthetic and scientific values, and most notably, the provisioning of potable water.

An estimated 95% of the world's available liquid freshwater supply is groundwater, and more than half of the world’s population relies on this supply for consumption and agriculture4. Globally, the human demand for groundwater is ~3.5 times the actual volume of aquifers5.

This situation will only deteriorate as the human population continues to grow, and the intensification of drought events will increase the demand on groundwater for agricultural irrigation6.

Provisioning of potable water is one of the most important ecological services associated with subterranean organisms7, given that bacteria and invertebrates are essential in maintaining clean groundwaters by enhancing carbon turnover, attenuating and degrading harmful contaminants, and even eliminating pathogenic microorganisms from the aquifer4.

But the services provided by subterranean organisms extend beyond that.

For example, cave-roosting bats form the largest congregations of mammals, and they play crucial ecological roles as insect pest controllers, seed dispersers, pollinators, and nutrient recyclers8.

This well illustrates the importance of subterranean ecosystems to human societies and the integrity of ecological systems, but also reminds us about how little we still know about these secluded environments9,10.To emphasize the urgency of protecting subterranean biodiversity, the year 2021 was elected the International Year of Caves and Karst (later extended to 2022).

Yet, the subterranean biome is still systematically overlooked in global biodiversity targets and climate change agendas.

In a recent letter to Nature Climate Change, we showed that only 6.9% of known subterranean ecosystems overlap with protected areas globally7.

Importantly, most of these subterranean ecosystems are protected simply because they occur within protected areas established for surface species or habitats, and therefore not designed to account for their vertical dimension7.

To rectify this omission, we established a consortium with representatives from 23 nation-states and seven indigenous groups, and proposed a roadmap to guide the conservation of the subterranean biome through 2030 and beyond11. On paper, these calls for action emphasize a positive trend.

Yet, if the warnings of scientists are not supported by quantitative evidence on what constitutes critical threats and conservation priorities, all of our efforts are merely ‘whistling in the wind’2.

Subterranean ecosystems are some of the most understudied ecosystems on Earth, and we are only now beginning to fully appreciate their potential as eco-evolutionary resources.

Therefore, we must confront a prickly question: What prevents the establishment of effective protection of subterranean biota and their inclusion in global conservation goals?The goal of DarCo is to devise a cost-effective and adaptive conservation plan to incorporate subterranean biodiversity in the EU Biodiversity Strategy for 2030.

In pursuing this goal, we seek to broadly engage with key stakeholders and the public, increasing awareness about subterranean ecosystems to ensure their effective preservation in the long run2.

To this end, we have established a research consortium composed of international researchers in the field of subterranean biology and conservation science.

The consortium is large (11 countries, 13 units) because we brought together scientists operating in aquatic (groundwaters) and terrestrial subterranean ecosystems.

Accordingly, we will be able to cover the breadth of subterranean habitats and taxa across Europe within a unified framework and shared databases.

Our consortium includes leading scientists on subterranean biology operating across main subterranean areas in the continent and oceanic islands, curators of main databases on subterranean species distributions and traits, and researchers holding expertise in taxonomy, ecological modeling, phylogenetic methods, functional diversity, spatial prioritization, and conservation biology.

As for gender equality, we have a 60:40 male-to-female ratio in designated team members. The project is articulated in five interconnected and modular work packages (WPs).