Extinction Rebellion wants to force governments to cut carbon emissions and avert a climate crisis it says will bring starvation and social collapse.

Extinction Rebellion climate protesters dug up the lawn of Trinity College, Cambridge on Monday, as part of a week-long series of demonstrations in Britain's ancient university town.

The activists dug up the grass in front of the 16th-century "Great Gate", digging channels in the turf with shovels and pitchforks and planting Extinction Rebellion flags.

Trinity had ramped up security measures, closing the college, library and chapel to tourists for the week, so the protesters were not able to access the central "Great Court."

"The College respects the right to freedom of speech and non-violent protest but draws the line at criminal damage and asked the protestors to leave. The College is liaising with the police," a spokeswoman for Trinity said in a statement.

"Academics at Trinity are actively engaged in research to understand and develop solutions to climate change, and taking practical steps forward," the statement said.

An email to Trinity students said "we expect disruption to continue in Cambridge this week, and should continue our patience and resilience with the access arrangements, in the spirit of protecting College, our community and environment."

Extinction Rebellion says it wants non-violent civil disobedience to force governments to cut carbon emissions and avert a climate crisis it says will bring starvation and social collapse.

"Trinity College must cut ties with fossil fuel companies and stop trying to hawk off nature for profit," Extinction Rebellion Cambridge on its Facebook page. "Oh, and it should take the opportunity to replace the lawn with flowers. Spring is just around the corner after all."

In anticipation of the week's protests, another of Cambridge's colleges, St. Catharine's, closed the main gate leading to its 17th-century court over concerns that Extinction Rebellion protesters would set up a campsite on the grass.

"One of Extinction Rebellion's oppositions is to green space being kept behind walls and only accessible to those in power and privilege," an email sent to students by the college's head porter said.

"Although our Main Court is actually open for viewing, there is a concern they may try to take it over and possibly camp on it," the email said.

Earlier this year, a group of students at the University of Oxford set up a camp in the front quad of St John's college for five days, to protest the college's investment in fossil fuel companies.

Inspired by this, climate protesters in Cambridge put up tents on the lawn in front of King's College.