On a drizzling October morning in Trafalgar Square, I arrived to speak at an Extinction Rebellion protest. A colourful array of tents served as backdrop to a makeshift kitchen dishing out steaming bowls of porridge to sleepy protesters. Police officers watched over two elderly activists splayed on the cold, damp tarmac, their arms locked together inside a concrete barrel. Close by, volunteers had erected a shaky wooden tower to lift another two rebels up and away from the police’s reach. An energetic group of drummers cheered them on, raising the temperature of the crowd.

I looked for the event’s organiser and asked her for directions to the venue where I was slated to give an early morning speech. “It’s here,” she told me, pointing to a wooden pallet. “Stand on this. Just speak. They will come.” I raised my voice to compete with the drummers, and stared out at the empty space in front of me. It started to rain. And before long, a crowd of hundreds appeared.

The Extinction Rebellion uprisings in London in April and October 2019 were courageous, home-grown and colourful. I witnessed sacrifice and generosity, collective action and joy. The bright tugboats, tie-dye-wearing crowds and collective hedonism pointed to a momentarily different London: one without commercial outlets flogging T-shirts, where food was free to those who needed it, streets were absent of car fumes, and people joined together in defiance of the law.

This has been the year of environmental protest. On Fridays across the world, school children have streamed out of classrooms and on to the streets, taking over urban centres with home-made placards: “There is no planet B!”; “I’m missing my science class for this!”; “I’ve seen smarter cabinets at Ikea!”. In more than 6,000 cities across over 200 countries, nearly 11 million people have marched in the Fridays for Future movement, sparked by the defiant actions of Swedish teenager Greta Thunberg.

Has it been enough? As the activist and author Naomi Klein argues in her recent book On Fire, these leaderless environmental protests will stand or fall depending on whether they have a plan. The risk, as with all political crises, is that they can be exploited by those seeking to instigate their own political reforms – policies that harden borders, erode democratic rights and fuse resource scarcity with anti-immigrant sentiment.

This is why a concrete plan for the transformation of the economy to secure social, economic and ecological renewal is imperative. Extinction Rebellion has three demands. First, the movement insists the UK government tell the truth about climate science and declare a climate emergency; second, it should pledge to halt biodiversity loss and reduce greenhouse gas emissions to net zero by 2025; and finally, the government must be guided in its decisions about climate and ecological justice by a democratic citizens’ assembly.

That the UK government has declared a climate emergency and agreed to hold citizen assemblies suggests Extinction Rebellion’s tactics might be working. But biodiversity loss and climate breakdown have their roots in an economic system wedded to growth based on high carbon use and toxic emissions. Without structural reform, government action will leave intact the economic causes of the environmental crisis: capital flows and the exploitation of fossil fuels.

Reforming the economy so it serves democracies is a key tenet of the Green New Deal, the plan that has been gaining political support on both sides of the Atlantic. Taking inspiration from Franklin D Roosevelt’s New Deal – a series of programmes enacted to save the US economy during the Great Depression of the 1930s – the Green New Deal is based on the understanding that finance, the economy and the ecosystem are bound together. In the US, the youth-led Sunrise Movement and Democratic congresswoman Alexandria Ocasio-Cortez have taken up its mantel; in the UK, meanwhile, the Green Party has pledged a Green New Deal, while Labour has agreed to a Green Industrial Revolution.

Environmental politics has traditionally involved exhortations to individual action: use reusable pens, carry a canvas tote bag, change the kind of light bulbs you use, buy local vegetables. This year, the green movement has adopted a different tenor. Extinction Rebellion and the school climate strikers recognise that responsibility lies with governments, not individuals. Rather than fixating on whether we recycle, proponents of a Green New Deal demand grand structural changes to the global economy.

But if Extinction Rebellion is to have a future, a fourth demand must be added: governments must subordinate the finance system to the interests of society and the environment, subjecting our global economy to public, not private, authority. In the three years after the Paris Agreement was adopted by consensus in late 2015, JPMorgan Chase, the largest bank on Wall Street, reportedly lent $196bn to fossil fuel companies in China, Africa, Europe and Canada. According to the charity Rain-forest Action, much of this lending funded ventures such as ultra-deep-sea drilling and Arctic oil extraction. It is bank lending, as the environmental activist Bill McKibben argues, that is “the oxygen on which the fire of global warming burns”. That was the message of my speech on that wet, gloomy October day in Trafalgar Square.