The environmental affairs title was founded by Edward Goldsmith in 1970. He edited the title until 1990, handing over to his nephew Zac Goldsmith, who remained editor until 2007 and is now a director of the company that owns it.
The Ecologist website will be revamped in June to coincide with the end of the print edition but would, Goldsmith promised, maintain its commitment to investigative journalism and coverage from environmental experts. Later this year, an online archive will be made available.
The magazine has a print circulation of 20,000 a month and a cover price of £3.50. To reduce its environmental impact it is printed on recycled stock using vegetable-based inks and instead of being flown to the US, is sent by ship.
The title is a relative latecomer to digital publishing, with a website first launched in 2005 and its first digital magazine a year later.
Zac Goldsmith said: "Relaunching the Ecologist online is in keeping with both the magazine's own credentials and with the zeitgeist of the digital age.
"When the magazine was launched, it was almost a voice in the wilderness. It is immensely gratifying to all those who care about the environment that most of the issues the magazine has espoused for 39 years have now moved into the mainstreams of political and social thinking."
Earlier this month, Dennis Publishing said that Maxim magazine would abandon print and become online only, while the April edition of US music magazine Blender is to be the last, although it will maintain a web presence.