“News is what someone wants suppressed; all the rest is advertising.” That maxim is overly reductive – would a medical breakthrough make the cut? – but captures an essential truth. The instinct to share information has always been matched by the instinct to prevent its spread. Andrew Pettegree’s history The Invention of News demonstrates how the sphere evolved over centuries and yet how many current issues are recognisable in its early days: from the blunt use of force by the powerful to the state’s deployment of propaganda dressed up as news and the crude pursuit of business interests.

So the pressures on news are hardly new – but they shrink or swell, and at times these swirling forces can amass to become a perfect storm. A new study says that media freedom around the world has fallen to the lowest level for at least a decade. The report by the freedom of expression campaign group Article 19, working with V-Dem, a political and social database, shows that diversity and independence is under growing threat in democracies such as Brazil and Hungary as well as authoritarian regimes such as China. “Turkish media is under immense pressure from the government, more than at any point in history,” one veteran correspondent told the Guardian. Frequently – as in Turkey, or indeed Cambodia or Poland – this tightening is part of a broader turn towards repression.

The problem is not only one of the state. Governments, officials, organised crime and other powerful interests employ measures ranging from libel suits and commercial ruses through to harsh laws and violence. When Daphne Caruana Galizia, who had led the Panama Papers investigation into corruption in Malta, was killed by a car bomb in October it made headlines worldwide. But her case is exceptional for its geography rather than its brutality. Unesco says that on average a journalist is killed every five days for bringing information to the public. New technologies have allowed digital surveillance and brought harassment through social media – sometimes fuelled by political leaders denigrating journalists. If anyone doubts how toxic the atmosphere can become even in a country guaranteeing freedom of the press in its constitution, Walmart’s website has just removed a T-shirt (offered by a third party seller) reading “Rope. Tree. Journalist. SOME ASSEMBLY REQUIRED”.

There are other challenges too. In the US there is concern that the rightwing billionaire Koch brothers have agreed to put $650m into Meredith Corp’s purchase of Time. They have a record of huge donations to libertarian causes and groups denying climate change, and of attacking unions and workers’ rights. Meanwhile, the growth of the internet has increased competition – not only from new media organisations, but through the expansion of advocacy or plain propaganda masquerading as journalism. And Russia and China are pumping money into the global expansion of state media, promoting government messages or simply casting doubt on reports in western media. These attempts are – like other challenges – a kind of compliment, however unwelcome. They testify to the impact and necessity of journalism: the powerful will always seek to control the spread of inconvenient information.

Defending the freedom of the press and its role in upholding the public interest is more essential than before. This will require renewed commitment and inventiveness, and not only in harnessing new technology. Collaboration with other media outlets can be a source of strength – as when 96 partners, including the Guardian, revealed the secrets of the global elite’s hidden wealth in reporting on the Paradise Papers. But a still greater source is the support of audiences, and their demand for honest, accurate reporting. Fighting off challenges is not enough. The media must keep reminding people why it counts to win the trust and commitment of readers and viewers and thereby maintain its freedom.