University of São Paulo: Caves of Brazil: an underground treasure to be discovered, but already threatened

Une of the most unknown treasures of Brazilian biodiversity is literally hidden underground. Few people know this, but pervading the subterranean bowels of the Amazon, the Cerrado and all the great national biomes there is a hidden universe of thousands of caves, inhabited by hundreds of unique species in nature and hundreds of thousands of years of petrified climate history and of life on the planet. There are more than 20,000 caves already cataloged in Brazilian territory — out of a total that, according to some specialists, could reach 300,000. And this underground treasure could be threatened, the researchers warn, due to changes in environmental legislation.

Most of these caves were only recently discovered. Until 2009, just over 6,000 caves were known in the country; since then that number has increased by 235%, and it continues to rise. The main “culprit” for this is a decree published in November 2008 ( Decree 6640), which created a new classification of caves and started to require the environmental licensing of activities potentially impacting them, such as agricultural projects, mining and infrastructure works. In this licensing process, which became mandatory, many new caves were eventually discovered. And, along with them, hundreds of new cave species — including fish, crustaceans, arachnids and a variety of other invertebrates — as well as countless landscapes, underground rivers, waterfalls, grandiose halls, adorned with fantastic speleothems, and others breathtaking geological formations.

“An invisible world”, in the words of geologist Francisco William da Cruz Junior — better known as Chico Bill —, a professor at USP’s Geosciences Institute (IGc) and one of the many researchers committed to promoting 2021 as the International Year of Caves and of the Karste , organized by the International Union of Speleology and supported locally by the Brazilian Society of Speleology (SBE).

The amount of news is so great that scientists are barely able to process so much information. So far, around 250 species of animals that live exclusively inside caves (called troglobites) are known, according to an unprecedented (not yet published) survey conducted by researchers Jonas Gallão and Maria Elina Bichuette, from the University’s Underground Studies Laboratory Federal of São Carlos (UFSCar). “Most troglobites are endemic”, that is, they are animals that only exist within a single cave or a single cave system, explains Maria Elina, who graduated from USP and also advises graduate students at the Ribeirão campus Black from USP.

This is the number of species formally described by science — with name, ID and proof of residence, let’s say —; but the “real” number of troglobites that inhabit the darkness of Brazilian caves is certainly much greater. Researchers estimate that the number of new species already collected, but not yet officially described, could reach 1,000. “With each new expedition we make, new species come to the surface. The description queue is gigantic”, says researcher Rodrigo Lopes Ferreira — better known as Drops —, from the Underground Biodiversity Sector of the Federal University of Lavras.

Maria Elina is more conservative and estimates the number to be around 500 — still a huge amount. This, considering only the animals already collected in past expeditions, which biologists are able to hold in their hands, look under a magnifying glass and infer that it is (probably) a new species. Not to mention, therefore, the countless unknown species that must exist in the underground depths of the thousands of caves that are yet to be discovered in Brazil. Making a simple calculation, if the estimate of 300,000 caves is correct and only 1% of these caves harbor an endemic troglobite, there will already be 3,000 species new to science.

The waiting list is mainly due to the small number of taxonomists (scientists specialized in the description and classification of species) with expertise in these more peculiar groups of cave animals.

Troglobite means life (bio) in caves (troglobule). They are very peculiar animals, with highly specialized morphological and physiological characteristics for life in the underground environment. The most common examples are reduction or absence of pigmentation and eye structures (since they do not need to produce melanin or see), lengthening of appendages (such as legs or pincers) and increase in sensory structures (such as antennae or whiskers), which they use to detect food and find your way in darkness. Most belong to the group of invertebrates, such as spiders, scorpions, beetles, centipedes and crabs. Among vertebrates, only fish, such as the blind catfish from Iporanga ( Pimelodella kronei), 20 centimeters long, which is endemic to the caves of the Alto Ribeira Valley, in São Paulo. It is a blind and carnivorous fish, which feeds on small aquatic invertebrates and cockroaches or crickets, which may fall into its icy waters.

In addition to troglobites, which are exclusively underground, there are troglophile organisms, which can live both inside and outside caves (such as some species of crickets and spiders), and trogloxenes, which inhabit caves but need to get out of them at some point to complete its life cycle. Of this last group, the most classic example are cave bats, which sleep on the roof of underground cavities but need to leave them daily to feed on fruits or insects – and, in doing so, they provide a very important ecological service for seed dispersal. in nature and the control of agricultural and urban pests. They are also the main importers of organic matter into the caves, through their feces (the famous guano), which serves as food for many of the invertebrates that live there.

In this sense, caves are essential for many bats, just as bats are essential for many caves. A cave in Tocantins, called Gruta dos Moura, houses 26 species of these flying mammals — a world record. “There are more species of bats in a single cave than in several countries in the world”, compares biologist Enrico Bernard, a specialist in bats and coordinator of the Laboratory of Science Applied to Biodiversity Conservation, at the Federal University of Pernambuco. In the Caatinga and in the north of the Amazon, according to him, there are caves with gigantic populations, of up to 150,000 bats.

“Caves are considered one of the last frontiers of biological research in the world”, as are the canopy of rainforests and the ocean depths, says Bernard. “They are hotspots for discovering species.”

Of the seven species of bats considered to be threatened with extinction in Brazil, four are cave dwellers, and are threatened precisely because of the loss of caves they depend on to survive, according to the researcher.

Since 2008, according to Decree 6,640, the presence of endemic or endangered species has been one of the criteria used to designate caves as having “maximum relevance”, which is currently the only category with a legal guarantee of preservation in Brazil. “The underground natural cavity with the maximum degree of relevance and its area of ​​influence cannot be the object of irreversible negative impacts, and its use must be made only under conditions that ensure its physical integrity and the maintenance of its ecological balance”, says Article 13 of the decree. On the other hand, caves classified as having high, medium or low relevance “may be the object of irreversible negative impacts, through environmental licensing”.

If, on the one hand, the licensing requirement provided a boom in the discovery and study of caves since 2008, on the other hand, the decree opened loopholes for the destruction of these environments. Until then, according to the original wording of Decree 99,556, of 1990 , all caves enjoyed full protection, and could only be used “within conditions that ensure their physical integrity and the maintenance of their respective ecological balance”.

“The number of known caves is directly associated with the economic pressure to use these caves”, explains speleologist Cruz Junior, from USP. “We got to know more caves in recent years, not thanks to an investment in science, but because the sector that wants to detonate these caves is obliged to carry out licensing”, adds Bernard.

new threats
By fits and starts, the scientists had even been living peacefully with the new decree — taking advantage of the best it had to offer and avoiding the worst it had to offer. New attempts to change this legislation, however, have once again echoed the fear of a threat to Brazilian caves in the scientific community. “With so many cattle passing by, it is clear that the caves would not remain unscathed”, says biologist Rafael Ferreira, a doctoral candidate at the São Paulo State University (Unesp) in Rio Claro and second secretary of the Brazilian Speleology Society (SBE).

“More than ever, caves are under severe threat,” says geographer Allan Calux, president of SBE. The first alarm sounded in 2019, when the Ministry of Mines and Energy proposed a new wording for Decree 6,640, opening the possibility that even the most important caves “could be impacted or even destroyed”, according to researchers report in a published article in June, on the Mongabay news site. The proposal, according to them, received a favorable opinion from the Federal Attorney General’s Office and was sent to the Ministry of the Environment, but has not yet been put into effect.

The second warning came with the bill that radically eases the environmental licensing rules in the country. Approved in May this year in the Chamber of Deputies, and now awaiting consideration by the Federal Senate, PL 3729 exempts several activities — including agriculture and livestock — of environmental licensing, and also creates a new modality of “self-licensing”, in which enterprises are authorized to issue their own licenses — including for the installation of mining tailings dams. Add to that the weakening of federal control agencies, such as Ibama and ICMBio, and the threat equation is set. “Everything is possible now in this new scenario”, evaluates Calux.

Although PL 3,729 does not directly mention the caves, the relaxation of licensing could have serious consequences for them, warn the scientists. That’s because caves can be dark and deep, but they’re not isolated from what’s going on on the surface. On the contrary: “If you destroy the external environment, it also gets inside”, says Ferreira. In particular, through the rivers, which are like the arteries of caves. If surface developments silt up rivers or pollute the water that runs into caves, underground life will be directly affected by this. And because the environment inside caves is usually quite stable, any small change can have very significant consequences—perhaps even making it impossible for some organisms to survive.

“The cave is very dependent on its surroundings; most of the food comes from outside it”, explains Maria Elina. If the forests that bats use for food are cut down, and the bats disappear, for example, all the organisms that depend on the organic matter they bring into the cave will starve to death.

“You can extinguish a cave species without even touching the cave”, sentences Ferreira. Or, who knows, with such self-licensing, ignore the existence or even bury entire caves, without the proper precautions. “To make licensing more flexible is to release the destruction of caves that we didn’t even have the chance to visit”, warns Cruz Junior. Referring to your previous speech, it would be like transforming the “invisible world” into a ghost.

geological diversity
How is it possible to have so many unknown caves — or not registered — in Brazil? The estimate of 300,000 possible caves in the country is by researchers Jocy Brandão Cruz and Luís Piló, in the Speleology and Environmental Licensing guide , published in 2019 by the Chico Mendes Institute for Biodiversity Conservation (ICMBio). It takes into account the extent of geological formations in which soluble rocks predominate, conducive to the formation of caves — called karst landscapes, or simply karst — and makes an extrapolation, based on the number of caves already known for each type of relief.

“It seems safe to say that, today, less than 5% of the existing caves have been identified”, write Brandão and Piló. “Our speleological potential is certainly in the range of a few hundred thousand caves. Just by way of comparison, in countries that are more developed in the identification and exploration of caves, such as Italy and France, with areas equivalent to the State of Minas Gerais, around 40 thousand caves are known. The lack of research, the small number of speleologists, the difficulties of access, among other reasons, justify the little knowledge we still have about the Brazilian speleological potential.”

It’s perfectly possible, according to speleologists, that there are huge caves hidden out there in the Brazilian underground, waiting to be discovered. Large caves do not necessarily have large portals; they can have simple entrances or camouflaged in hard to reach areas. Just venturing into them to find out. Son Doong, the world’s largest cave by volume (38.5 million cubic meters) in Vietnam, was only discovered by researchers in 2009, for example. The largest cave in Brazil is Toca da Boa Vista, in Campo Formoso, in the hinterland of Bahia, with 114 km of mapped galleries, and its true extension only began to be scientifically illuminated in the late 1980s — despite its entrance already known by the local population for a long time.

Biological diversity is not the only thing that draws attention in Brazilian caves. There is also an incredible geological diversity to be admired and studied. The most common are caves in limestone, which is an abundant rock that is highly soluble in water; but there are also caves formed in various other types of rock, such as quartzite and sandstone, each with its own characteristics. A peculiarity of Brazil, which has emerged in recent years, is the large number of iron caves — mainly in the region of Carajás (PA), which is the largest producer of iron ore in the country.

Preserved in these rocks are thousands of years of geology and climate history in these regions, which scientists can “read” through the chemical elements that are deposited by water in the process of formation of speleothems (stalactites and stalagmites). They are rock cores that hold information about the climate and environment around these caves at the time they were formed, just like ice cores extracted from glaciers. “Each stalagmite is a natural patrimony of information from the past”, says Cruz Junior, an expert on the subject. Information that, according to him, is essential to understand what can happen in the future.

The same goes for the fossil and archaeological remains, commonly preserved in caves — as they, historically, have always been a place of shelter for humans and other animals. Serra da Capivara, in Piauí, for example, houses some of the oldest vestiges of human occupation in the Americas; as well as the caves in the region of Lagoa Santa, in Minas Gerais, where the so-called “people of Luzia” lived.

“We have a huge speleological heritage in Brazil”, says the explorer, photographer and scientific promoter of caves Daniel Menin, whose images illustrate this report. An invisible world, which needs to become visible to be preserved.

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