On a hot day in July 2012, researchers scoured a familiar forest, gathering 594 soil samples across 1.3 square miles of land. The single day’s worth of sampling uncovered high levels of biodiversity, with more than 167,000 kinds of bacteria, archaea (microorganisms similar to bacteria), and eukaryotes (multicellular organisms and tiny critters) found in the soil.
That soil came from New York City’s Central Park.
“We didn’t expect to find so much diversity,” said Diana Wall, Colorado State University biologist and a coauthor of a study on Central Park’s dirt that was published Wednesday in the journal Proceedings of the Royal Society B. “Central Park has been around a long time, but it’s still remarkably diverse.”
Wall, with the other researchers, started at the American Museum of Natural History and gathered the samples throughout the day, putting them in plastic bags and sending them to Yale University for chemical and biological testing and analysis.
The final tally found the soil contained 260 times as many species as the park boasts of flora and fauna combined. The results came as a surprise: Only 8.5 percent to 16.2 percent of the organisms discovered in park soils, depending on their type, had been previously entered into existing databases that describe microbial life.
For any area, soil biodiversity can mean higher sustainability for all life forms. The tiny organisms in soil cycle nutrients, break down organic matter, sequester carbon, and hold water for plants. Without a functioning ecosystem below the ground, the food web up top wouldn’t work. For researchers, finding such expansive biodiversity amid one of the densest cities in the world was a bonus.
But Central Park isn’t a weird and strange world—its soil has an abundance of species that have been brought in from all over the world. Antarctica was the only continent that didn’t have soil species overlapping with the park.
Why would one of the United States’ most urban parks be so biologically diverse? Years of heavy park management have introduced a plethora of plant species, fertilizers, and chemicals that have encouraged different species to exist in a small area—a sort of “melting pot park” emulating the city surrounding it.
The researchers also found that, unlike plants and animals aboveground, underground organisms are not much affected by heat or humidity at the surface. Instead, their patterns are better predicted by the carbon and acidity of the soil surrounding them.
Wall said that a better understanding of these organisms may lead to new antibiotic drugs or even new types of yeast with which to brew beer. “There are a lot of organisms that may be useful in ways we don’t even know yet,” she said. “That’s the whole idea behind the field of bioprospecting—searching for useful products in nature.”
She pointed out that just like aboveground, there is a rich ecosystem in underground soils. Some bacteria are predators, keeping the populations of others in check—and they all work together to form a complete food web, which helps humans. “The microorganisms work to clean our soils, transform nutrients, and get rid of pollutants and pests,” Wall said. She hopes to study the soil bacteria at other parks.