John Moratelli has never seen anything like it. And he's mortified.

Having lived on Sydney's lower North Shore for more than 25 years, Moratelli is no stranger to stories of the odd tree being illegally cut down.

But the scale of tree vandalism inflicted on bushland adjacent to an affluent street of multi-million-dollar homes in Castle Cove, where 265 trees were callously cut down or poisoned, has left him flabbergasted.

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"I have never heard of anything approaching this level, nothing like it," Moratelli, the Willoughby Environmental Protection Association president, told 9news.com.au.

"I've heard of individual trees, maybe a handful of trees, but 265 trees?

"It's in another realm entirely."

The affected area measures 3600 square metres – the size of 14 tennis courts – and the number of trees killed is also set to rise as the poison used to wipe out a range of species spreads through the earth and contaminates other root systems.

An 80-year-old angophora costatas, which can reach heights of 30 metres when fully mature, has been poisoned. A range of Christmas bushes, old man banksias, she oaks, cheese trees and tea trees have also been destroyed or infected with toxic poison.

Pictures of the crime scene show trees felled and hacked down, and what appears to be a bottle of poison and a protective rubber glove in scrub.

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