Bellamy first came to public prominence as an environmental consultant at the time of the 1967 Torrey Canyon disaster; he published Effects of Pollution from the Torrey Canyon on Littoral and Sublittoral Ecosystems in Nature . He has written and presented some 400 television programmes on botany, ecology, and environmental issues. Bellamy is the originator, along with David Shreeve and the Conservation Foundation (which he also founded), of the Ford European Conservation Awards and has published scientific papers (between 1966 and 1986) and many books.
In 1980, he released a cover version of the song "Brontosaurus Will You Wait For Me?" (backed with "Oh Stegasaurus") which he performed on Blue Peter wearing an orange jump suit. It reached number 88 in the charts. During this period he was a popular television presenter. He was parodied by Lenny Henry on Tiswas with a "grapple me grapenuts" catchphrase. He once voiced an advert for the blackcurrant drink Ribena, which claimed that 95% of British blackcurrants were used in Ribena. (This has now been changed to "Nearly all British blackcurrants are used in Ribena".)
During the 1980s he replaced Big Chief I-Spy as the figurehead of the I-Spy range of children's books and to whom completed books were sent in order to receive a reward.
In 1983, he was jailed for blockading the Australian Franklin River in a protest against a proposed dam. On 18 August 1984 he leapt from the pier at St. Abbs Harbour into the North Sea. In the process he officially opened Britain's first Voluntary Marine Reserve, the St. Abbs and Eyemouth Voluntary Marine Reserve. In 1997 he stood unsuccessfully against the incumbent Prime Minister John Major for the Referendum Party. Bellamy credits this campaign with the decline in his career as a popular celebrity and television personality, stating in 2002:
"In some ways it was probably the most stupid thing I ever did because I'm sure that if I have been banned from television, that's why. I used to be on Blue Peter and all those things, regularly, and it all, pffffft, stopped."
He is a prominent campaigner against the construction of wind farms in undeveloped areas. This is despite appearing very enthusiastic about wind power in the educational video Power from the Wind produced by Britain's Central Electricity Generating Board.
In 2010 Bellamy starred in an advert for Churchill Insurance Company, in which The Churchill Dog house sits for Bellamy.
David Bellamy is currently the President of the British Institute of Cleaning Science (BICSc) and is a strong supporter of the BICSc plan to educate young people to care for and protect the environment. The David Bellamy Awards Programme is a competition designed to encourage schools to be aware of, and act positively towards, environmental cleanliness. The 2010/2011 Awards are now accepting applicants and further information on this can be found on the BICSc website.
In his foreword to the 1989 book The Greenhouse Effect Bellamy wrote:
"The profligate demands of humankind are causing far reaching changes to the atmosphere of planet Earth, of this there is no doubt. Earth's temperature is showing an upward swing, the so-called greenhouse effect, now a subject of international concern. The greenhouse effect may melt the glaciers and ice caps of the world causing the sea to rise and flood many of our great cities and much of our best farmland."
Bellamy's later statements on global warming indicate that he subsequently changed his views completely. In 2004, he wrote an article in the Daily Mail in which he described the theory of man-made global warming as "poppycock". A letter he published on 16 April 2005 in New Scientist asserted that a large percentage (555 of 625) of the glaciers being observed by the World Glacier Monitoring Service were advancing, not retreating. George Monbiot of The Guardian tracked down Bellamy's original source for this information and found that it was Fred Singer's website. Singer claimed to have obtained these figures from a 1989 article in the journal Science, but no such article exists. Bellamy has since stated that his figures on glaciers were wrong, and announced in a letter to The Sunday Times in 2005 that he had "decided to draw back from the debate on global warming".
His opinions have changed the way in which some organisations view Bellamy. In 2005 a spokesperson for the charity Plantlife, of which Bellamy had been president for 15 years, stated that "it would be wrong to ask him to continue [as president]". The Royal Society of Wildlife Trusts stated in 2005 "We are not happy with his line on climate change", and Bellamy was succeeded as president of the Wildlife Trusts by Aubrey Manning in November 2005.
In October 2006 the New Zealand Herald reported that Bellamy had joined the New Zealand Climate Science Coalition, a group trying to refute what they believe are unfounded claims about man-made global warming In May 2007 Bellamy and Jack Barrett jointly authored a paper in the refereed Civil Engineering journal of the Institution of Civil Engineers entitled 'Climate stability: an inconvenient proof'. In this report they argue that the widely prophesied doubling of carbon dioxide levels from natural, pre-industrial levels was not only unlikely but would also amount to less than 1 degree C of global warming.
In June 2007, The New Zealand Centre for Policy Research (founded by Muriel Newman formerly an MP in the neo-liberal ACT Party) published an opinion piece by Bellamy stating amongst other things that "There are no facts linking the concentration of atmospheric carbon dioxide with imminent catastrophic global warming".
Bellamy complained in November 2008 that his dissent from global warming has resulted in rejection for his BBC TV programme ideas. However, The Guardian newspaper has pointed out that Bellamy stopped making television programmes in 1994, some ten years before his first public statement showed scepticism about climate change.