Central Park's Soil Is Home to Microbes Found All Over the World

Being one of the most-visited parks in the world, it's hard to imagine even a single shrub remaining undiscovered in the hundreds of years since Central Park opened. But that's in the sunshine. Beneath its surface, Central Park is home to a stunning array of microbial biodiversity, according to a new, comprehensive survey of the park.

Central Park is surprisingly biodiverse, with at least 393 plant species and roughly 350 animal species. Yet it's what's lurking underground that piqued the interest of a team of researchers from Colorado State, the University of Colorado, the University of Minnesota, and Yale.

In new research published in Proceedings of the Royal Society B, the team details how it took nearly 600 soil samples from Central Park and analyzed the DNA of the microbes they found. According to the researchers, 122,081 bacterial, 1659 archaeal, and 43,429 eukaryotic phylotypes—a term used to classify single-celled organisms that can be tough to classify via other methods—live below the surface of the park.

"Not only did Central Park harbour high levels of below-ground diversity, we found that most of these phylotypes were undescribed," the authors wrote. Just 16.2 percent of their genetic sequences turned up matches in the Greengene database for microbial genomes, and 8.5 percent in the SILVA database.

Biodiversity above ground is affected by an area's climate factors—in this case, urban construction, along with the gardening, fertilizing, and other human impact endemic to a park—but below the surface, tiny organisms are less affected by these restrictions. Central Park alone contains subterranean biodiversity on par with that of tropical regions, the Arctic, and the desert.

This same factors make Central Park "ideally suited for investigations of below-ground diversity, because the soils found throughout the park are highly variable in their habitat characteristics in part due to the intensive development of the Park since its establishment in the mid-1800s," the authors write.

"The broad range of cover types and management practices (e.g. fertilizer and compost applications, mulching, irrigation) within the Park allowed us to examine the factors structuring soil communities across environmental gradients while holding climatic conditions nearly constant," the authors add.

To see how the park's soil microbiome compares to more natural sites, the researchers compared 52 randomly selected Central Park soil samples to 52 samples collected from global biomes as varied and distinct as Antarctic cold deserts, tropical forests, Arctic tundra, and grasslands.

The results were striking: species in Central Park's underground microbiome are largely also found elsewhere in the world. Out of 2497 of the "most abundant" phylotypes in the sample sets (e.g. ones that weren't found to be extremely rare in soil samples), nearly 95 percent "were shared between Central Park and the global soils," while 1.3 percent of that group was unique to the park. This may be due to the varied and distinct properties of the many soils in the park itself.

"The management practices used in Central Park not only promote a diverse array of soil conditions, but they also appear to result in those urban soils harbouring a breadth of below-ground taxa and community-type rivals that found collectively in soils from across the globe," the researchers write.

According to the team, their study is a step forward for the study of underground microbiomes, having identified a significant number of previously unrecorded organisms. It also reminds us of the incredible diversity of life on Earth, no matter how small, even in the heart of one of the most developed urban areas on the planet.