As Internet users contribute increasing amounts of content to the information universe, professional journalists must be increasingly vigilant to ensure veracity and accuracy.

Bertrand Pecquerie is director of the Paris-based World Editors Forum. Larry Kilman is director of communications for the affiliated World Association of Newspapers. Editors and publishers from more than 100 countries belong to these professional organizations.

A media revolution occurred on July 7, 2005, though not many realized it at the time.

That was the day when terrorist bombings struck the London Underground. Citizens on the scene flooded newspapers and broadcasters with pictures, recordings, and reports of what had happened. Many media outlets were quick to use the consumer-generated content.

But perhaps an even greater watershed occurred on December 11, 2005, when the Buncefield oil depot explosion in the United Kingdom prompted an unprecedented response from citizen journalists who sent thousands of e-mails, photographs, and video clips of the disaster to news Web sites long before professional journalists reached the scene of the early morning blast about 43 kilometers from London.

The BBC, for example, received more than 6,500 e-mails with videos and photographic coverage of the explosion and the oil fires, compared with 1,000 in the aftermath of the London train bombings. The first pictures and video footage came in minutes after the explosion.

The head of BBC News Interactive, Pete Clifton, had this to say to the news Web site MediaGuardian about the impact of the citizen-produced content: "The range of material we received from our readers was absolutely extraordinary. Videos, still pictures, and e-mails poured in from the moment the blast happened, and it played a central part in the way we reported the unfolding events."

On the day of the explosion, half a million users logged on to the BBC Web site to view the pictures and videos. Citizen media had become a permanent and essential part of the mix.

Democratizing the Media

Today, rare is the media outlet that is not in the process of expanding the two-way street that digital media have created between news outlets and their users. The multitude of new electronic distribution channels has put everybody just a keyboard away from producing news content themselves — true in the developed world and growing in the developing world as well.

Or, as citizen journalism pioneer Dan Gillmor puts it, "in a world of ubiquitous media tools, which is almost here, someone will be on the spot every time."

Year by year, the growth of digital media has democratized the publication of words and pictures of all kinds, once the monopoly of the printed press and the broadcasters. Consider:

• During a rampage by an armed student at Virginia Tech University in the United States, major broadcasters, including CNN, frequently opened the airwaves directly to student blogs and other eye-witness accounts, producing an immediacy in coverage impossible through other sources.

• More and more bloggers are invited to sit in media-reserved seats at a variety of news events. About 10 percent of people on the media list for New York Fashion Week this year were bloggers.

• The developer of the Big Brother reality TV series, Endemol, has started producing daily, user-generated, TV news shows in the Netherlands. Citizen reporters submit news videos that are compiled into a news report on IK OP TV (Me on TV).

• In Pune, India, the Sakaal Group of newspapers has created a weekly "citizen supplement" that is entirely written by readers. "People want positive news and positive things to read about," says sub-editor Deendayal Vaidya. "They are already mired in their own lives and crises. They want to be inspired." Nearly a thousand readers, the majority of whom were never published before, have written for the supplement.

• The influential French daily Le Monde is providing blogs to its subscribers. Among other things, the paper encourages readers to keep electronic journals on their travels, the best of which can be accessed through the travel pages of the newspaper Web site.

• In Chile, the national tabloid Las Ultimas Noticias (the Latest News) saw a 30 percent growth in circulation after its editors began checking which stories were most read on their Web site and then used the information, in part, to determine what stories appeared in print. Although this isn't user-generated content, it shows how users are increasingly influencing media's editorial choices of content.

The notion of "citizen journalism" was first proposed in Dan Gillmor's book in 2003, We the Media: Grassroots Journalism By the People, For the People, with this now well-known assertion: "News is no longer a lecture, it's a conversation." Gillmor's argument, similar to the philosophy of online encyclopedia Wikipedia, was that "collective knowledge and wisdom greatly exceeds any one person's grasp of almost any subject."

During this period, start-up grassroots projects were gaining momentum and credibility. It was said that if newspapers ignored them, they risked alienating some of their established — and a large part of their future — readership.

Whom Do You Trust?

Nowadays though, the appellation "citizen journalism" is increasingly disappearing, to be replaced by the more comprehensive notion of user-generated content. There is no more reference to "journalism," a specialized profession with a unique set of rules and ethics, different from those of bloggers, who are no longer competing journalists but complementary content producers.

The wording "user-generated" also casts off the notion of citizenry and civic engagement. Content can be produced by consumers, readers, and commentators alike, but professional editors are needed to turn the content into "journalism."

The resulting magnitude of sources presents a challenge dating from the dawn of journalism: deciding which source is trustworthy. According to the Saturday editor of The Times of London, George Brock, "The most important question the consumer of news and opinion will ask herself or himself is the question they have always asked: Do I trust this source? Some [sources] will pass that test; some will fail. Open societies that want to stay open should keep setting that test." The emergence of user-generated content, a true cultural revolution, brings both opportunities and also considerable dangers that require society's vigilance.

On the plus side, citizens now have much greater control over how and when they receive information. They can react to it and participate in it if they choose.

The news business is becoming more of a dialogue between the providers and receivers of information, rather than an imposition of opinions and perspectives by an elite caste.

On the negative side, the Internet has opened up extraordinary new possibilities for the widespread and sometimes dangerous manipulation of information, which is difficult, if not impossible, to stem.

This phenomenon will increasingly place a heavy responsibility on professional journalists to maintain high standards of fact-checking, honesty, and objectivity. Editors are already spending enormous amounts of time verifying and authenticating user-generated pictures and text, and this will only become a more time-consuming part of their jobs. Blog posts and comments require careful and regular scrutiny.

If bloggers may not be bound to strict ethical codes, at the level of "professional blogs," there is a good deal of community-induced regulation. The Huffington Post scandal involving American actor George Clooney in March 2006 illustrated the vigorous checks and balances of the blogging community. When Ariana Huffington's crew posted an article based on a mishmash of Clooney's television interviews and passed them off as his writings, the actor did not hide his disapproval. Although site founder and author Arianna Huffington originally downplayed the affair, she was ultimately obliged to apologize, due to the overwhelming disdain arising from the blogosphere.

The very fundamentals of our democratic societies and the credibility of established media will be lost if we are unable to distinguish between true and false information.

The responsibility of news businesses is thus considerable. For the moment, there remains a significant preference of the majority of readers to access their information through traditional print products, with 1.6 billion readers of daily newspapers worldwide. Public opinion polls consistently show that news consumers are more likely to trust well-known and established news brands and to treat blogs and citizen-generated materials with more skepticism.

For example, a study of news consumers by the French free newspaper 20 minutes found that two-thirds of respondents consider news published in online participatory outlets "can't be considered as news" and they doubt the "veracity of their (the outlets') news."

It is essential to increase the media literacy of journalists, in particular, and citizens, in general, to help them assess the value and truthfulness of the information they receive.

At the World Association of Newspapers (WAN) and World Editors Forum (WEF), we strive to keep our industry apprised of these developments and how they will affect our businesses and society at large.

We periodically run campaigns to remind the public about the fundamental issue at stake when we talk about media freedom. One of the campaign slogans, "Freedom of the Press is Freedom of the Citizen," was never more true than it is today.

The WAN and WEF represent publishers and editors in more than 100 countries, working for 18,000 publications, including thousands of Internet news and information sites and blogs — editorsweblog.org, sfnblog.org, trends-in-newsrooms.org — that are now an integral part of the news business.

The opinions expressed in this article do not necessarily reflect the views or policies of the U.S. government.