Sir David Attenborough has said he feels "unbelievably lucky" to be turning 90.
The naturalist and TV presenter, who will celebrate the milestone birthday on May 8, spent Saturday afternoon opening Woodberry Wetlands in London to the public for the first time in almost 200 years.
Asked about how he feels about the birthday, he said: "The truthful answer is that I feel unbelievably lucky.
"I have friends, contemporaries, relatives, people who are my age, who can't walk about. I am unbelievably fortunate."
Sir David said access to the natural world is a "birthright" and should not be regarded as a luxury.
Woodberry Wetlands in Stoke Newington is a working reservoir which has been closed to the public since it was built in 1833.
Opening the 11-hectare wildlife oasis to the public, the naturalist said: "It's not a luxury this, you know. If it isn't there it's a great deprivation, and if it is there, it's what human beings deserve.
"We are part of it and if we lose contact with the natural world, you lose contact with a great source of pleasure and delight which is your birthright."
He added: "There's an awful lot of people, in the cities and elsewhere, who live in a world of concrete and asphalt and brick and glass.
"So it's a huge, huge benefit."
Sir David said children - even in urban areas - are naturally drawn to the world around them.
He said: "Give a young person half a chance. You watch kids at six, eight years old, just being riveted to see what these extraordinary things are at their feet."
From 1955-1980, chlorine and sodium phosphate was used by Thames Water in the reservoir, preventing wildlife from growing - but since that practice ended, wildlife has flourished, prompting the London Wildlife Trust to turn it into a public nature reserve.
David Mooney, who led on the development of the site, paid tribute to the volunteers who "built the project from the ground up".
He said: "They come frostbitten at six o'clock in the morning in February, rain coming down, and they'll be in the reedbed managing it and helping it flourish.
"It's remarkable to see how wildlife, give it half a chance, stop pumping it full of chemicals and it will take hold again."