New York may be known as a concrete jungle, but throughout its five boroughs, there are thousands of parks, playgrounds, and other recreational facilities. They vary in shape and size—as well as intended uses—but these spots are an invaluable resource for New Yorkers.

But parks require maintenance and upkeep—and according to a new, somewhat damning report, “serious cracks are showing” in many of the green spaces maintained by the city.

The 53-page report, released by the Center for an Urban Future, found that the average NYC park is 73 years old. (The oldest parks in each borough are Bowling Green in Manhattan, Commodore Bark Park in Brooklyn, Drew Playground in the Bronx, Daniel Beard Mall in Queens, and Veterans Park in Staten Island.) Many of these spaces are feeling the effects of old age, but maintenance is being neglected where it’s needed the most, resulting in infrastructural problems.

“New York City was blessed with having a tremendous program of construction during the Works Progress Administration,” Adrian Benepe, who headed up the Parks Department under Mayor Michael Bloomberg, says in the report’s introduction. “But all of those structures—bridges, highways, parks, pools—they’re all nearing the end of their natural life. So I’d say a very, very big bill is coming due, in the billions.”

Indeed, the study estimates that in order to bring the city’s parks into a state of good repair, an unprecedented investment of close to $6 billion would be needed.

Of the 65 parks surveyed in the study, almost half had aged drainage systems that caused flooding problems for several days after a rain. More than 20 percent of park bridges that were inspected had serious deterioration and city-maintained parks along the waterfront were found to be 76 years on average. The report also found that the average city park hasn’t seen a major renovation in the past 20 years, and that 20 percent of parks have not received major infrastructure upgrades in the last 25 years.

Per the report, in fiscal year 2017, the city funded a mere 15 percent of its state-of-good (which includes major infrastructure and capital repairs) needs, spending less per capita than other major but smaller cities. Add to that, the Parks Department is “chronically underinvested in maintenance staff” with just 150 gardeners citywide (or one for every 133 acres), 27 electricians, 11 maintenance staffers assigned to marinas, and one carpenter to cover 148 miles of coastline.

While this all sounds somewhat dire, CUF has also outlined some recommendations for how the city can address these issues, including:

Give the Parks Department more funding, both for capital projects and its expense budget.

Add more staff to handle maintenance and operations.

Use new, innovative materials to improve the long-term sustainability of parks.

Expand pre-existing initiatives that have been doing good work (Community Parks Initiative, Parks Without Borders, and Anchor Parks).

Meanwhile, the Parks Department notes that the city has been working toward the revitalization of parks around the city.

“This administration has invested in strengthening the City’s parks system from top to bottom,” said a spokesperson for the agency. “Capital programs including the $318-million, 65-park Community Parks Initiative and the $150-million Anchor Parks project are bringing the first structural improvements in generations to sites from playgrounds to large flagship parks.”

You can read the report in its entirety here.