Joe O'Neil can't remember a time when London wasn't nicknamed the Forest City.

O'Neil, the former chair of the city's advisory committee on heritage, said it's not the numbers, but a green history that crowned London as the Forest City.

"London was originally a huge thick forest," he said. "It was the city you came upon out of the forest … people couldn't believe the trees."

O'Neil said the city's founding families were mesmerized by vast green lands during the late 1700s that were lost to development in 1826 when London was established as a municipality.

He said more trees were cleared during both World Wars to meet construction demands.

Jill-Anne Spence, the city's urban forestry manager, said several neighbourhoods in London were also built from local woodlands.

"When we were looking to build and establish our city, there was a significant amount of vegetation and a lot of trees," she said. "Many that were used to build our communities and homes and we were called the Forest City because of that."

Remnants of London's natural history are preserved in places like the Sifton Bog, Westminster Ponds and Medowlilly Woods.

O'Neil said London briefly lost its claim to the Forest City after development projects stripped the land of its green spaces. However, replanting strategies are underway to reconnect the city to its roots.

For every 1,500 trees that are chopped down annually due to poor health, the city replants 5,000.

"We want to ensure that our urban forest is more sustainable for future and current generations," said Spence.