Hundreds of people are staging "protest of one" road blocks on Saturday to demonstrate against what they say is a lack of action by governments on climate change.
The protests have been organised by pressure group Extinction Rebellion (XR) and see individuals sitting alone in busy roads wearing signs with messages about their fears for the future.
The protest began at 11am on May 1 - two years exactly since Parliament declared a climate emergency.
One woman sat in the road in Machynlleth with a sign saying "I am terrified".
Lynda Duffill, a 53-year-old mental health trainer and volunteer manager from north Pembrokeshire who sat in the road in Haverfordwest, said: "I fear for the next generation's future. I work with young people and have two young adult children myself.
"They deserve a life free from the difficulties that climate breakdown could bring."
Protests took place in towns and cities across the country, including Nottingham, Birmingham, Oxford, Bradford, Newcastle and Swansea.
XR said in a statement that despite its carbon-cutting targets - with Boris Johnson recently announcing plans to cut emissions by 78% by 2035 - the UK Government is moving too slowly.
It cited multiple reports finding the UK will miss its targets unless ministers take rapid action.
Another protest was staged in Carmarthen, with a person seen blocking traffic in the high street.
XR spokeswoman Gully Bujak said the Government was good at generating positive headlines but accused it of failing to have a plan to meet its goals.
Ms Bujak said: "The UN People's Climate Survey found that 81% of people in the UK believe that we're in a global emergency.
"The Government needs to commission a national Citizens' Assembly on climate and ecological justice, because even if politicians are scared to face the truth, ordinary people are ready for action."
Saturday's protests coincided with a number of demonstrations against the Police, Crime, Sentencing and Courts Bill.
The Bill was drafted partly in response to previous disruptive action by XR and also the Black Lives Matter movement.
The proposed legislation would give police in England and Wales more powers to impose conditions on non-violent protests - including those deemed too noisy or a nuisance, with those convicted liable to fines or jail terms.
A Home Office spokesman said: "The right to protest is a cornerstone of our democracy, but over recent years we have seen an increase in the use of disruptive and dangerous tactics."
He added: "These new measures will not stop people from carrying out their civic right to protest and be heard, but will prevent large scale disruption - enabling the silent majority to get on with their lives."