Their feelings are easy to understand. Many trees will have been around for as long as a person has been alive and may seem immutable. Individual trees may be connected with special memories for a person – picnics, weddings or special walks.

In a more general sense, Council surveys suggest that the trees are a big part of why we value the city — they are strongly identified with Christchurch’s Garden City identity.

But City Council tree officer Dieter Steinegg says nothing that grows is forever. To the untrained eye they may seem as strong as ever, but many of the city’s grand old trees are starting to lose their grip on life and are becoming potentially dangerous, he says.

“It’s not so surprising that we’re coming up to a period when a lot of trees are nearing the end of their lives,” Mr Steinegg says. “Many of them are of the same generation, more than 100 years old and all planted around the same time. They’re like people all born in the same year – been to school together, grown up, grown elderly and now is the time for the farewells.”

Elderly trees suffer internal ills that weaken them – root rot and fungal diseases carried in the soil or through the air that can spread between trees like a contagion.

And local conditions mean it is not possible to compare the aging of a tree here and that of a tree from the same species in its native country, where it might remain strong and vital for decades longer.

The city needs to start thinking now about how it will replace such a large number of important trees, Mr Steinegg says.

“Because there’s such a big peak coming we need to start thinking now about replacing them,” he says.

“We’re talking about the whole city, thousands of trees over the next 15 to 20 years.

“What types of trees do we want to replace them with, how do we want the city to look 30 to 40 years from now. Those are the kinds of questions we need to ask and answer and we need to start planning for it now.”