(CNN) -- A 104-year-old Australian scientist who is set to end his life at a clinic in Switzerland later this week told CNN that his life was no longer worth living and said he hoped his story would lead to the legalization of assisted dying in other countries.
David Goodall, a respected botanist and ecologist, is due to die at the Life Circle clinic in Basel on Thursday, after traveling to Europe from his home town of Perth, Australia earlier this month.
The grandfather-of-12 and longtime member of pro-euthanasia group Exit International said his life stopped being enjoyable "five or 10 years ago," in part because of his failing mobility and eyesight.
"My life has been out in the field (working), but I can't go out in the field now," said Goodall, who must be pushed everywhere in a wheelchair, during an exclusive interview with CNN in his hotel in Basel on Tuesday.
"I would love to be able to walk into the bush again, and see what is all around me," said the father-of-four, who during his long life has had three wives and moved to Australia from London as a child.
"I could still enjoy birdsong," he added. "But my lack of vision would seriously impair it."
Goodall said he would have preferred to have died when he lost his driver's license in 1998, adding that the loss of independence at 94 was a big moment in his life.
"At my age, I get up in the morning. I eat breakfast. And then I just sit until lunchtime. Then I have a bit of lunch and just sit. What's the use of that?" said the scientist, who flew business class to Europe earlier this month after supporters raised $20,000 for his campaign.
Fighting 'cruel' laws
Euthanasia is illegal in Australia, though the state of Victoria is planning to allow assisted dying from mid-2019. Goodall's home state of Western Australia is currently debating whether to introduce the policy.
Several US states have a form of physician-assisted suicide, as do a small number of countries including Japan, Belgium and Switzerland.
Goodall attempted to take his own life a few weeks ago but ended up waking up in hospital instead, where doctors judged that he was a risk to himself. He was only discharged after an independent psychiatric review commissioned by his daughter.
The scientist described his treatment as "cruel," adding, "they oblige one to stay alive, when one hasn't got anything to live for."
Goodall said he felt "resentful" that he had to travel to Switzerland to die, and hoped that his story would lead the Western Australian government to change its laws.
"I'm looking forward to it," he said of his death in two days time. "I'm happy that this period beforehand has been used to interview me, and I've brought the ideas of euthanasia to light."
"What I would like is for other countries to follow Switzerland's lead and make these facilities available to all clients, if they meet the requirements, and the requirements not just of age, but of mental capacity."
Goodall: I don't fear death
Goodall said he did not fear death, but instead will "welcome it when it comes."
"The process of dying can be rather unpleasant, but it need not be -- and I hope it won't be for me," he said.
On Thursday, doctors will place a intravenous needle filled with sodium pentobarbital into Goodall's arm and he will administer the lethal drug himself.
Exit International founder Philip Nitschke told CNN earlier in May that the option of traveling to Switzerland for medically assisted suicide was open to anyone, provided they had sound reason and fulfilled certain criteria.
"My belief is that any rational adult should have the ability to access the drugs which would give them a peaceful, reliable death," said Nitschke, whose organization was instrumental in helping Goodall organize the trip.
While a little hard of hearing, and reliant on Nitschke to push his wheelchair, Goodall appeared to have lost none of his sense of humor on Tuesday, wearing a top inscribed with the words "Aging Disgracefully."
Born in London in April 1914, just months before the outbreak of World War I, Goodall said he remembered "creeping under a table in northern London suburbs to escape the air bombs being dropped."
The respected botanist and ecologist went on to hold academic positions across the world, including in the United Kingdom, the United States and Australia.
After his retirement in 1979, Goodall edited a 30-volume series entitled Ecosystems of the World, written by more than 500 authors. In 2016, the professor was awarded the prestigious Order of Australia Medal.
Some of his happiest memories of his life included his many trips abroad, including to Fiji and Sweden.
His advice for young people on how to live a good life was "to take whatever opportunities arise -- as long as those opportunities don't involve harm to other people."
When asked what his final thought would be before his life ends on Thursday, Goodall was sharp as ever.
"I'll be thinking about the needle and hoping they aim right!" he replied.