Collaborative Science for Groundwater Biodiversity Conservation

Abstract

Lost in the alarm and broader narrative on global trends of biodiversity collapse, an ecosystem is silently vanishing under our feet: groundwater. “Out-of-sight, out-of-mind” describes not only groundwater the resource, but to even greater effect, groundwater the ecosystem. That is, while groundwater is generally recognized as an invisible resource, it is rarely acknowledged or celebrated as an invisible habitat.

Depletion and quality degradation of groundwater ecosystems trigger impacts on diverse, highly specialized, and often locally endemic biota, ranging from microbes to cavefish. The extent to which groundwater ecosystems are threatened is alarming: underground biological extinction is already happening (Humphreys 2022). The full breadth of this challenge is unknown, yet the large-scale and widespread depletion and quality degradation of groundwater would suggest that groundwater ecosystem collapse may be extensive and with concerning implications.

First, all the essential services linked to the maintenance of a well-functioning groundwater ecosystem, such as contaminant degradation, oxygenation, and carbon turnover regulation, would be lost. Without those, groundwater quality is bound to degrade, leading to the potential proliferation of harmful viruses and bacteria. Furthermore, this impoverishment could cause detrimental cascade effects on the myriad of ecosystems that depend on groundwater, for example, rivers, lakes, grasslands, and forests. As climate change and aridification intensify, the reliance of these ecosystems on groundwater will inevitably increase, reinforcing the need for sustainable groundwater management policies and strategies (Gleeson et al. 2020).

Multiple exciting recent developments have enabled a better understanding of groundwater ecosystems. The number of species documented in subterranean groundwater-dependent ecosystems is now almost 50,000 (Martinez et al. 2018), a number that far exceeds that of fish globally. These species deliver innumerable provisioning, regulation, and cultural ecosystem services below and above ground (Griebler and Avramov 2015). Simultaneously, the marked emergence of continental to global groundwater modeling in recent decades presents a particular opportunity to link groundwater dynamics and patterns of biodiversity with land use, climate, socioeconomic, and political change across broad contexts. In continuity with the concept of “ecohydrogeology” (Cantonati et al. 2020), we perceive a grand opportunity to better link the groundwater biology and hydrology communities and raise here the critical need to leverage such collaborations to enhance and empower groundwater ecosystem conservation and management. A handful of efforts to map terrestrial and aquatic groundwater-dependent ecosystems have emerged over recent years (Link et al. 2023; Huggins et al. 2023a; Rohde et al. 2024; Saccò et al. 2024), yet acknowledgement of groundwater biota in hydrogeological studies remains rare, and aquifer management impacts continue to be unquantified. Likewise, thorough representation of hydrological processes is equally sparse in groundwater biology studies. Both fields have blind spots that mutual collaboration can address.

Groundwater is increasingly recognized as a resource embedded in a diverse network of systems (Huggins et al. 2023b), which include social, economic, cultural, ecological, biological, hydrological, and geological components. Broadening the “tent” of groundwater science to include the various systems and disciplinary forms of expertise that relate to groundwater could enable a more fruitful environment for this needed interdisciplinarity. Indeed, there is great potential for groundwater hydrogeologists and biologists to lead the way on this, and we pinpoint three priority areas, each followed by an actionable initiative. (1) Collaborative research—organize dedicated workshops, conference sessions, and special issues focused to nurture and facilitate collaboration between hydrologists, biologists, and conservation scientists. (2) Conservation policies—incentivize the collection of empirical subterranean ecological data to support informed, and field-verified conservation and management actions. (3) Social awareness—establish international days to promote groundwater biodiversity issues, which could include the establishment of a World Groundwater Day, in line with existing days dedicated to rivers and lakes, or through advocating a subterranean or groundwater theme for an upcoming World Biodiversity Day.

Overall, these actions could meaningfully raise the profile of groundwater ecosystems. Advancing these actions, however, will not be trivial, and deepening the integration of hydrogeology with biology will face challenges relating to the fuzzy definition and concept of groundwater-dependent ecosystems, the acquisition of geographically extensive data in subterranean ecosystems, and the feasibility of incorporating biological components into hydrological modeling frameworks. Yet, in a world dominated by the language and discourse of crisis, we remind ourselves and readers of the fundamentally optimistic orientation of the scientific enterprise (Paskins 2020). To protect groundwater biodiversity worldwide, now is the time to be bold and think outside of the (subterranean) blue box.