One of the city’s last remaining salt marshes, a patch of land straddling the Hutchinson River Parkway in the Bronx, could hold secrets about our changing climate—both what has been and what could be.

Four years ago, a team of scientists began taking core samples here—10-foot-long segments extracted from the earth—and analyzing every inch of the dirt for clues about what was happening in the world at the time the sediment was deposited.

They found that the samples contained more than 1,500 years of detailed climate and environmental history.

As The New York Times reported,

The soil told of local pollution, indicating the use of municipal refuse incinerators, which peaked in 1937, and offering clues of events farther afield, such as evidence of the aboveground nuclear weapons tests conducted in the 1950s and 1960s.

It even showed a small peak in the concentration of lead during the years of WWI (when there was an increase in production and use) and a decline during the Great Depression.

But most importantly, the core samples showed the tidal flows and sea level rise. The results were startling.

According to the authors of the resulting report, published in the journal The Holocene, the current rate of sea level rise “is the fastest that NYC has experienced for >1500 years.”

The data showed that since 1821, the seas have risen roughly 1.5 feet, and alarmingly, they are expected to rise by the same amount over just the next 40.

These measurements are consistent with other measurements made in the western North Atlantic, and indicate that we are on a dangerous trajectory.

Again, from The New York Times:

More than $25 billion worth of infrastructure will be under direct threat from flooding through the coming decades, scientists believe, including seven hospitals, 183 hazardous waste sites and the homes of nearly 100,000 people.

So, what do these results tell us? Simple: climate change is happening, sea levels are rising, and New York City needs to be doing more to protect our people and our infrastructure. The clock is ticking.