Of the great variety of different ecosystems on our planet earth, there are some that call our attention much more, either because of their proximity, because of their characteristic and striking features, or because they are home to flagship species, and we ensure their conservation. However, other ecosystems, more hidden, less noticeable, and even less studied, we tend to overlook, and sometimes completely ignore. This is what happens, for example, with oceanic abyssal ecosystems, those that form in the icy Antarctic lands, or, as is the case, underground ecosystems .
In the great conservation plans, forests and wetlands, or iconic species such as the Iberian lynx or the capercaillie, are always taken into account. In the sea, coral reefs and animals as characteristic as cetaceans or sea turtles are of concern.
However, “in the great global conservation agendas, underground ecosystems and their diversity have traditionally been forgotten” . This has been stated by the research group of the National Museum of Natural Sciences (MNCN – CSIC) in the recent study published in the prestigious scientific journal Biological Reviews .
The structure of an underground ecosystem
Underground ecosystems, such as those formed by caves, function ecologically in a similar way to how islands function. Although most have at least one connection to the outside environment, these entrances generally represent a very small portion of the total extent of the underground environment. This, added to the fact that the species in a cave have evolved to adapt to that environment, and do not usually tolerate living outside, means that the animals in one cave system do not have any gene flow with neighboring cave systems. In the long term, this phenomenon causes speciation events that cause, as a direct consequence, that the living beings that inhabit a cavernous system are endemic to said system.
In the subterranean environment there is a strong selective pressure that forces the populations to certain adaptations, such as long limbs, absence of eyes and pigmentation, or highly developed chemoception. These extreme adaptations make troglobite living beings —as those that live in caves are called— highly specialized organisms practically incapable of inhabiting any other environment.
Although subterranean ecosystems are among the least studied environments in the world, they nonetheless present a unique fraction of the Earth’s biodiversity . This biodiversity is exposed to a significant and growing number of anthropogenic threats.
Impacts on underground ecosystems
Many activities and events of anthropic origin threaten the valuable and practically unknown troglobic biodiversity. It highlights pollution , both organic and inorganic; surface water infiltrates through the interstices of the rocks and frequently ends up in caves, forming lakes, lagoons and underground rivers, which are refuges for troglobic biodiversity. Given the high level of specialization of the animals that live there, the pollution that comes with these waters can cause disastrous effects on the underground ecosystem. The change in the structure of surface habitats —sometimes caused by changes in land use— also has a negative effect on this aspect.
Other impacts, however, enter directly into the ecosystem from the outside. The use of caves for the exploitation of their resources or as a tourist attraction , supposes a drastic and destructive alteration of the subterranean ecosystems, which can cause the extinction of species that have not even been discovered yet. And of course, invasive alien species , and the pathogens they may carry, represent a high risk, although avoidable if proper prevention is carried out.
How to protect underground ecosystems?
There is very little scientific information on the subject. In general, there are two ways to promote the conservation of these ecosystems: direct conservation and indirect conservation —and they are very similar to those proposed for terrestrial and marine ecosystems—.
Direct conservation includes environmental protection measures, regulation in legislative terms, and of course, restoration systems —such as the eradication of invasive species, the decontamination of waters or the restoration of habitats—.
Indirectly , risk analysis and prioritization systems based on scientific methods allow the best actions to be applied in each case in detail; continuous monitoring of the state of ecosystems feeds these analyzes of reliable data, and this adds to education, training and social awareness .
In the aforementioned study they carry out a systematic review of the studies focused on the conservation of underground ecosystems since 1964. And from all this they draw some conclusions. On the one hand, many of the measures that work to protect terrestrial or marine ecosystems can be successfully applied to subterranean ecosystems; There’s no need to “reinvent the wheel,” the authors caution. Future research should focus on identifying solutions and generating new ideas to address specific problems in underground ecosystems, without reiterating existing knowledge.
They also highlight a great inequality in the focus of the studies . Most focus on terrestrial caves, and more specifically, bat and insect populations. There is hardly any information on the microbiota of interstitial spaces, or on marine or coastal underground ecosystems, which, say the authors, are underprotected. The authors also highlight the lack of information on the effects of some global threats, such as climate change.
Underground ecosystems are part of the biosphere , such as coral reefs or wetlands; they are environments under great pressure due to disturbances of human origin and largely forgotten in terms of their protection. That is something that should make us reflect.
This article is dedicated to José María Salgado Costas, entomologist,
pioneer of the study of the troglobital fauna of Spain, and mentor.
References:
Mammola, S. et al. 2022. Towards evidence-based conservation of subterranean ecosystems. Biological Reviews, n/a(n/a). DOI: 10.1111/brv.12851