The natural world is collapsing because of how we live and we will go with it unless we act now.
People must rethink how to produce food and look after nature, campaigners urged as a new UN study outlined the damage being done to the natural world.
The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) report warns that declines in nature are accelerating as a result of human activity, which in turn threatens people's well-being.
The global assessment comes in the wake of widespread protests on the streets of London and other UK cities over the twin crises of environmental damage and climate change, in which more than 1,000 people were arrested.
Lorna Greenwood, spokeswoman for Extinction Rebellion which led the protests, said: "The natural world is collapsing because of how we live and we will go with it unless we act now.
"Not only are we destroying nature but we're worsening our own health and making it harder for us to feed ourselves.
"It's time to rethink how we grow food, travel and look after the countryside.
"It may mean hard choices but the rewards are enormous. Within our lifetime we could see nature restored and our children's future secured."
She said protesters had no choice "but to rebel until our world is healed", but said the shift in public attitudes in the last fortnight meant it was becoming politically realistic to rethink how to produce food and look after nature.
Responding to the report, Greenpeace UK's executive director, John Sauven, said: "The world's leading scientists have once again hit the emergency button over the state of our planet.
"It's time political and corporate leaders stopped making empty promises and started acting to prevent us sliding towards another mass extinction of life on Earth.
"It's absolutely vital that we urgently change the way we use the land and oceans to end this war against nature," he said, calling for end to forests being cut down for palm oil and soy production and the exploitation of the oceans.
He urged the UK Government to restore peatlands, plant millions of trees, provide ocean sanctuaries around the coasts and support a shift from meat and dairy to "healthy, plant-based meals".
Abi Bunker, director of conservation at the Woodland Trust, said it was essential to address the climate and natural environment crises together.
She said natural systems on which people depended in the UK were under pressure from habitat and wildlife loss, use of pesticides, pollution, overgrazing, invasive species and pests and diseases, and climate change.
More native trees and expanded woodland cover were a "huge part of the solution" to tackle damage to the natural environment, absorb carbon emissions and help cope with the impacts of climate change, such as flooding.
"To make an impact, new woodland creation, using natural regeneration wherever possible, will need to happen on a faster and far greater scale than ever before and be sustained over several decades," she urged.
Professor Richard Bardgett, president of the British Ecological Society, said: "The IPBES report makes it abundantly clear what will happen to the natural world if we continue as we are.
"This matters - not only for conserving the nature we see around us, but also for maintaining and increasing our own well-being and prosperity.
"Biodiversity and thriving ecosystems are critical for sustaining the natural resources on which our economy depends."
Alexandre Antonelli, director of the Royal Botanic Gardens, Kew, said the report "confirms that that we can't just preserve, we must reverse the trend by increasing biodiversity locally, regionally, and globally".
He warned that, despite previous ambitious goals to protect biodiversity - the variety of life on Earth - under the UN Convention on Biological Diversity which were due to be met by 2020, the report showed the outcome was "almost a complete failure".
"We must learn from that process in order to not make the same mistakes. We just can't miss this chance -- lest it be our last."
Mark Wright, director of science at WWF, said the report painted a "terrifying picture of a broken world".
He added: "Last week, MPs approved a motion to declare an environment and climate emergency. This report shows we have no time to waste in turning those words into action.
"We are the first generation to truly understand what we are doing to our world and the last who can do anything about it."
Emily Beament is the environment correspondent for the Press Association.