The UK off-shoot of Wikipedia has insisted the site was "definitely not dying" after research suggested thousands of volunteer editors across the world had left.
Work by Felipe Ortega from the Universidad Rey Juan Carlos in Madrid found that 49,000 editors deserted the site in the first three months of this year - 10 times the number in the same period of 2008.
Spokesman for Wikimedia UK Michael Peel said it was too early to say whether Mr Ortega's numbers were accurate, and that it would depend on the definition of a Wikipedia "editor".
He said: "Wikipedia is very open so anyone can come along and edit, so you do get a constant flux.
"Wikipedia is definitely not dying. It's freely licensed which means that content that has been added will be there forever."
There was speculation that tighter rules governing how content is added had put people off, but Mr Peel said the system also meant vandalism was more easily removed.
Pilot projects are under way in the US to make it easier to add and edit content, and to upload images.
In the UK a scheme will start in February to gather information from museums on artefacts to add to existing entries.
Mr Peel said getting experts to support the site provided part of the solution to getting a balance between freedom and minimising inaccuracies.
"We're trying to engage a bit more at the moment with people who are very knowledgeable, people who are experts, so working with museums was the obvious next step," he said.
Mr Ortega built a computer program to analyse editing history on Wikipedia.
He told The Times: "If you don't have enough people to take care of the project it could vanish quickly. We're not in that situation yet. But eventually, if the negative trends follow, we could be in that situation."
Mr Ortega said later: "If the negative trend is maintained for too much time, say one or two years, eventually the project could enter a problematic phase.
"This is especially true for creating high quality content."
He said the best entries needed input from many different editors, and this was obviously harder to maintain with smaller numbers.
But Mr Ortega said Wikipedia could work on drawing in new users to survive into the future.
He said it should also concentrate on taking better care of contributions from academics and schools and making it easier to edit the encyclopaedia.