Strong winds sweep over the Rhön, a vast region of rolling, forested hills and pastureland in central Germany. Undeterred, Stefan Zaenker, leading a group of four volunteers, runs through his checklist alongside a forest road. Are rubber boots disinfected to prevent introducing potentially harmful microorganisms into the wetland? Are the team app and GPS functioning correctly? Have enough flags been packed?
When all is in order, Zaenker, 56, leads the group into a soggy alder forest. Its mission for the day: to locate and map as-yet-undiscovered springs and document any species inhabiting them.
A senior conservation official for the state of Hesse, Zaenker considers springs so important for human life and biodiversity that he — along with volunteers from the Hesse Association for Cave and Karst Research — spends much of his spare time conducting large-scale searches for them in the Rhön, which includes the German states of Bavaria, Thuringia, and Hesse, and in a nearby national park.
Conservation strategies around the globe focus on rivers, bogs, forests, reefs, and many other habitat types. Springs rarely get any special attention. In the United States, for example, springs do “not appear to be a prominent feature on the conservation radar,” says Kirsten Work, a zoologist from Stetson University in DeLand, Florida.
Springs are home to highly specialized species, some of which live outside by night and in the darkness of groundwater by day.
But for the biosphere, these tiny spots dotted across Earth’s land surface play a powerful role: They connect reservoirs of groundwater to the outside, sunlit world. Only so-called “fossil” aquifers — ancient bodies of groundwater that do not recharge — lack a link with the surface. Without a continual connection to groundwater, which also feeds rivers, many landscapes would quickly dry up and become hotter. In addition, springs are home to a wide range of highly specialized species, some of which live outside by night and in the darkness of groundwater by day.
Far too little is known about where springs occur and what species they harbor, Zaenker says. In a country like Germany, which has no wilderness but a very efficient bureaucracy, most people assume that everything in nature has already been discovered and mapped. This is not true, he claims: “I can stand right next to an impressive spring with water flowing out, but the official topographical map shows nothing.” Official maps denote springs with a blue dot, indicating they are habitats protected by law. Yet many — if not most — springs remained undocumented. “How are we going to effectively protect these important habitats or know if they dry up,” asks Zaenker, “if we don’t even know they exist?”
Left: A flag marks a helocrene spring in the Rhön region of Germany. Right: Stefan Zaenker takes a sample from a spring. Christian Schwägerl
After an hour of scouring the alder forest, the team has found and marked with flags eight new so-called helocrene springs, where water seeps diffusely from the ground into a marsh or bog. To the average person, they can look like puddles. But Zaenker recognizes much more in them. “See the bright green plant?” he points out. “That’s the alternate-leaved golden saxifrage, a species typical for springs.” The team logs the flags’ positions in a database, then measures pH levels and electrical conductivity to assess the water’s acidity and dissolved particle content. They collect water samples, identify more plants, and sift through leaves to find insects, mollusks, and crustaceans unique to these habitats.
Halfway around the globe, ecologist Larry Stevens is on a similar mission and is equally worried about the future of springs. In 2013, Stevens cofounded the Springs Stewardship Institute, a nonprofit science initiative linked with the Museum of Northern Arizona, and in 2023 he published Springs of the World: Distribution, Ecology, and Conservation. Stevens considers springs prime examples of “canaries in coal mines” because they act as early warning systems of water table decline and biodiversity loss.
Some experts use springs as sentinels for aquifer health, observing whether their temperatures increase or their discharges fall.
Stevens is particularly fascinated by the large number of highly specialized and endemic species found in and around springs. He points out that with constant temperatures and high purity, spring water offers unique living conditions. Springs are often isolated from one another geographically and many have been in place for millennia, characteristics that make them hotspots for new species to arise and refuges for species that have lost their habitats elsewhere. “Although miniscule in habitat area compared to rivers, lakes, and oceans, springs support more than 10 percent of U.S. endangered species, as well as thousands of other rare and endemic biota,” he notes. For example, the so-called Comal Springs riffle beetle is limited to a few springs in Texas, while the endangered White River springfish lives only in isolated warm springs in eastern Nevada.
While there are many spectacular springs — like the white Pamukkale terraces of Turkey, Blue Spring in New Zealand, or the hot springs in Yellowstone National Park — most are rather inconspicuous. That doesn’t diminish their importance, though. Every creek, river, pond, and lake starts with at least one, and often many, springs.
But public recognition of springs’ importance has diminished. Most people no longer retrieve water from springs but get it through municipal supplies. “Springs have been systematically piped, tapped, built over, and even today they are run over by forest trucks and polluted by excrements from cattle, fertilizers, and pesticides,” Zaenker says.
A tufa spring in the Neumarkt region in Bavaria, Germany. Christian Schwägerl
When the Swiss canton of Jura mapped a total of 1,750 known springs, half showed severe damage from piping or pollution or had been outright destroyed by development. In addition, groundwater levels in many regions around the globe are rapidly dropping due to over-pumping and diminished rainfall. Some scientists and conservation bodies have started to use springs as sentinels for aquifer health, observing whether their temperatures increase or their discharges fall.
Drawing on more than 40 years of data from 170,000 monitoring wells and 1,693 aquifer systems across the globe, scientists at the University of California, Santa Barbara, and other institutions determined in January 2024 that “widespread, rapid, and accelerating groundwater-level declines” are underway in many regions of world, in some cases by up to 50 centimeters per year. Sustained rain can help replenish aquifers, but this is not a given as the climate continues to change. In Germany, many months with intensive rainfall still haven’t balanced out a water deficit from six years of drought, satellite measurements show. In the Swiss survey, almost one in five springs had dried up or could no longer be located.
In 2023, Work, of Stetson University, warned that half of 126 springs in the U.S. for which long-term records exist exhibited declines in discharge. After assessing data on 10,000 springs in the U.S., Work now calls for a concerted effort to study springs and their ecosystems more intensively, as they are “likely to become even more important in the future as climate changes and their roles as freshwater refuges, temperature buffers, and bellwethers become even more important.”
One conservation official estimates that there could be as many as 5,000 species living at springs throughout Germany.
There is still a great deal that’s unknown about springs, Work says: “Where they all are, how exactly they connect with below ground, what biodiversity they support.” She notes that in Florida, springs provide a warm water refuge to manatees in winter and a cool water refuge for fish and other species in summer. According to a 2019 Florida Springs Institute assessment of 32 so-called “sentinel” springs in the Florida Springs Region, all were “slightly to greatly impaired, many are endangered or more seriously impaired, and some have collapsed.”
Probably the most comprehensive survey so far of the global health of springs was carried out by Stevens, of the Springs Stewardship Institute, who with his team evaluated information on about 300,000 springs in 75 nations. In all landscapes where their conservation status has been assessed, Stevens says, springs are “widely recognized as threatened and endangered ecosystems.”
Stefan Zaenker’s survey in Germany’s Rhön region stands out for its level of detail. After collecting water quality data, Zaenker unpacks a small, fine-meshed sieve and draws it through the water of a small muddy pond. Suddenly, a white animal wriggles in the sludge — a cave amphipod. This species usually lives in groundwater during the day, moving into surface water at night. “There are many such wanderers between worlds at springs,” says Zaenker. “The groundwater is alive, and these creatures help to purify it” by consuming organic detritus.
A Rhön spring snail (left) and fire salamander (right) found around springs in Germany. Klaus Bogon; John P. Clare via Flickr
Fire salamanders, which often lay their live larvae in spring areas, and flying adders – large, black-and-yellow-striped dragonflies– are among the most visible representatives of an otherwise cryptic fauna of copepods, mussel crabs, annelids, pseudoscorpions, dwarf spiders, and other groups. “What do we have here?” Zaenker asks, holding up a small black dot on his index finger. “A pea clam.”
The 15 volunteers supporting the mapping project have already found around 2,700 animal species at springs in the Rhön. Zaenker estimates that there could be as many as 5,000 species living at springs throughout Germany. Many specimens are hard to identify. Over the years, Zaenker has built up a network of 90 experts at natural history museums throughout Europe, to whom he sends samples and consults with. “Some species can only be distinguished based on genitalia or other details,” he says, “and some turn out to be new to science.”
The most cherished species in the Rhön — often featured on educational placards — is an endemic only two millimeters in size: the Rhön spring snail. According to Hans Boeters, a leading expert on spring snail taxonomy, Bythinella compressa has occupied larger territories in the past 2.6 million years. But as waters became more polluted and lower-elevation regions warmed, the snail was limited to the clean and consistently cold springs high in the Rhön’s rolling hills.
“With healthy springs,” says a conservationist, “young trees will have a better chance of surviving the next heat wave.”
Boeters is concerned about the species’ prospects of survival. “Spring snails are site-loyal,” he says, “and if a population is destroyed, there will be no recolonization.”
Managers of the Rhön biosphere reserve have started fencing off springs that still host the rare snail to exclude cattle. And pipes and concrete blocks are being removed so spring creatures can move freely between surface and groundwater. Eva Schubert, a conservation manager with Landesbund für Vogel- und Naturschutz (LBV), a conservation organization associated with BirdLife International, emphasizes the importance of springs for forest survival in a warming world. “With healthy springs,” she says, “the forest floor will be moister, and young trees will have a better chance of surviving the next heat wave.”
Over two days of reconnaissance work, Zaenker’s team found 50 springs that don’t yet appear on official maps. After returning home, Zaenker realized that over 20 years he has documented exactly 8,000 springs. “That’s about 10 times as many springs as are officially listed on the maps for this region,” he says. After each outing, he feeds his data into the official geographical information system of the forest authorities so they can avoid those springs during logging operations. Initially, his concerns fell on deaf ears there, he recalls. “Now, I regularly get invited to training courses to make forestry workers aware of springs and why they need protection.”
So far, Zaenker’s project has not changed the attitudes and awareness of official mapmakers. But when they are ready to represent all springs as protected habitats with blue dots, his vast database will be available for their use.
