Saturday's action on Lambeth, Westminster, Waterloo, Blackfriars and Southwark bridges gave bands and speakers the opportunity to address the crowds and followed a week of protests around the United Kingdom under the Extinction Rebellion banner.
On Monday, 22 people were arrested after protesters blocked traffic and glued themselves to entry gates at the Department for Business, Energy and Industrial Strategy. The Extinction Rebellion protesters are demanding the government takes more measures to tackle climate change.
"We've basically got three demands", said Gail Bradbrook, one of the organisers.
She said: "We need to be building resilience in our communities".
"People think that climate change is something happening to somebody else at some other time, but it's coming home".
"We'll know when governments are doing different things...."
Saturday's demo followed a wave of co-ordinated protests across the United Kingdom this week.
Police have arrested 85 people following a mass environmental demonstration.
The police have said the demonstrations were impeding Londoners and the emergency services from using the bridges which form a key part of the capital city's transport infrastructure.
Demonstrators take part in a pro-environment protest as they block Westminster Bridge in central London on November 17, 2018, to show anger at what they see as government inaction on climate and ecological issues.
The protesters later moved to Parliament Square where a rally was held and activists planted trees. "And we're also asking for a people's assembly so people can decide how the change happens".