Protesters, who had travelled from across the country to attend the event, cheered, waved Welsh flags and held placards in Welsh and English reading: “No Farmers, No Food”.
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They are objecting to proposals by the Welsh Labour Government to require more land to be set aside for environmental schemes.
A series of protests have already taken place across Wales but the event in Cardiff Bay on Wednesday was the largest by far, attended by thousands of farmer
South Wales Police had previously asked those attending not to bring tractors, meaning a line of the vehicles were parked along a road leading to Cardiff Bay.
The event saw speeches from farmers, Senedd politicians from the Welsh Conservatives and Plaid Cymru, as well as from former international rugby union referee Nigel Owens.
He told the cheering crowds: “In 2015, I was very privileged to referee the World Cup final in Twickenham – the proudest moment of my career.
“But today I’m even prouder to come and speak in front of good, decent people. An honour to be here to speak and to support you today as a fellow farmer.”
Mr Owens said he had dreamed of becoming a farmer since he was eight years old, and now had a small freeholding Meet the fitness influencer defying stereotypes about ageing
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“I do it became I care, because I’m passionate about the industry that we are in,” Mr Owens said. “But without farmers there is no food.
“There can be no Six Nations game in Cardiff next Saturday against France if there is no referee. There can be no food on the table if there are no farmers.”
Protesters placed wellington boots in adult and child sizes in front of the speakers.
Mr Owens said: “In decades time to come, we want to see people in those wellingtons, not empty ones.”
The protesters are objecting to the sustainable farming scheme (SFS), which is currently under consultation and would require 10% of a farmer’s land to be covered in trees in exchange for future funding.
Farming leaders say the scheme could result in 5,500 job losses.
The Welsh Government insists it is listening to farmers’ concerns and changes can be made.
Ioan Humphreys, a fifth-generation farmer from mid Wales, said: “I’ve got a two-year-old son sitting at home who loves every minute of being on the farm, and I am fighting for his future on that farm.
“I’m also here to make sure as farmers stick together and unite through this time of hardship regardless of who we are, where we come from, what we found or what we believe in, now is the time to stick together.”
He added: “Farmers are the heart and soul of our local communities and I for one am fed up of being treated like the villain.
“Where do the people thinking up these schemes think their food is going to come from when there’s farms ravaged by TB and we’re busy pruning trees.”
Those demonstrating have seen the support of the Prime Minister, Rishi Sunak, who told a gathering outside the Welsh Conservative conference last week that “we’ve got your back”.
Andrew RT Davies, leader of the Welsh Conservatives, thanked the farmers for demonstrating, telling them they were “sending a message to the Welsh Parliament”.
He said: “What we must continue to do and be allowed to do is produce that food, protect our environment.”
Rhun ap Iorwerth, leader of Plaid Cymru, said: “There is no Wales without rural Wales.
“We cannot have a vibrant rural Wales without its governments here in Cardiff and in Westminster being willing champions for it and backing it at every turn
“From the foods on our tables, to our living communities and to our rural environments, and the health of biodiversity in rural Wales, it is agriculture that binds all of this together.”
A Welsh Government spokesperson said: “Farming is very important to Wales and our economy and we want a successful future for Welsh farming.
“We have had a seven-year conversation with farmers to design future farming support and we are committed to continuing to work with farmers to develop the Sustainable Farming Scheme.
“This is a genuine consultation and no decisions will be taken on any element of the proposal, including how we achieve the requirement for habitat and trees, until we have conducted a full analysis of the consultation responses.
“We have been clear we expect changes to be made following the consultation, and we will continue to listen.
“The First Minister and Rural Affairs Minister provided an update yesterday on a number of key areas to support the sector.”
Superintendent Esyr Jones said: “South Wales Police respects the right to peaceful protest, and following discussion with the organisers we were able to ensure that the protest took place safely, lawfully with minimum disruption to the wider public.
“Bringing tractors and other agricultural vehicles into a busy city environment poses a risk to the safety of other road users and potentially restricts the movement of emergency services.
“However, working with the protest organisers and Cardiff Council a suitable holding area was identified meaning little disruption or delay on routes around Cardiff Bay and across the wider South Wales road network.”
