Those worries have to do with this city-state’s insatiable appetite for land. Singapore’s 5.7 million residents live on 277 square miles, a bit less than the area of New York City, but the land has to accommodate more than a municipality’s needs. It must hold the infrastructure of a country, including military bases, landfills, reservoirs, national parks and one of the world’s busiest airports and harbors.

More than 20 percent of the country is built on reclaimed land, leading its two immediate neighbors, Malaysia and Indonesia, to ban the export of sand to Singapore in order to protect their own land. And with plans calling for Singapore’s population to increase to 6.9 million by 2030, land is at a premium.

Part of the solution has been to look inward. In 2011, the government decided to smooth out a bend in the island’s north-south highway by cutting through Bukit Brown. Soon after, the government announced that within 40 years the rest would be paved over, too.

After watching many of their best-known monuments and neighborhoods leveled over the past decades, Singaporeans began to take action — a turning point that people here compare to the 1963 destruction of Pennsylvania Station, a Beaux-Arts masterpiece in New York City whose loss catalyzed historic preservation in the United States.

At their center is an informal group of two dozen volunteers who call themselves “Brownies.” They offer free tours and run a website that details the cemetery’s history and includes testimonials by locals and visitors.

One of the first Brownies was Raymond Goh, 54, a pharmacist who used to lead Halloween tours around the cemetery. (As in many parts of the Chinese cultural world, Singapore is obsessed with ghost stories and ghoulish legends.) After a while, Mr. Goh began to read the inscriptions on the tombstones carefully and was surprised at the antiquity of the graves.