Almost one-third of the world's farmable land has disappeared in the last four decades, with intensive agricultural practices severely impacting the ongoing viability of crop lands, a new study has found.

And the problem will only get worse if we don't act now, say experts, with current farming methods leading to what could be a disaster for food production in the near future.

"Erosion rates from ploughed fields average 10–100 times greater than rates of soil formation and nearly 33 percent of the world's arable land has been lost to erosion or pollution in the last 40 years," said Duncan Cameron, a plant and soil biologist at the University of Sheffield in the UK. "This is catastrophic when you think that it takes about 500 years to form 2.5 cm of topsoil under normal agricultural conditions."

In a new report presented this week at the United Nations Conference on Climate Change, the researchers warn that today's intensive agricultural system is unsustainable, with the heavy use of fertilisers – which themselves consume 2 percent of the world's annual energy supply – degrading healthy soils all over the world.

"You think of the dust bowl of the 1930s in North America and then you realise we are moving towards that situation if we don't do something," Cameron told Oliver Milman at The Guardian. "We are increasing the rate of loss and we are reducing soils to their bare mineral components. We are creating soils that aren't fit for anything except for holding a plant up."

The solution, according to the researchers, is to return in part to pre-industrial agricultural methods that helped to conserve crop lands before the advent of the modern fertiliser system.

"Historically, good soil management was supplemented by the collection and application of 'night soil', which is human excrement – a practice that continued into the 20th century," said one of the researchers, Colin Osborne. "In a historical example of the circular economy, this closed the nutrient loop, recycling organic nitrogen and phosphorus back into soil."

By applying manure directly to soil and rotating crops, we could begin the process of restoring soil's organic matter, structure, water-holding capacity and nutrients, the researchers say.

"We need to take land out of production for a long time to allow soil carbon to rebuild and become stable," Cameron told Milman. "We already have lots of land – it's being used for pasture by the meat and dairy industries. Rather than keep it separated, we need to bring it into rotation, so that that there is more land in the system and less is being used at any one time."

In addition, the researchers say biotechnology could help wean crops off the "artificial world" of fertiliser chemicals, giving them a chance to regain symbiosis with soil microbes. It won't be easy to overhaul the entire agricultural system, but the researchers say the alternative is unthinkable.

"We can't blame the farmers in this. We need to provide the capitalisation to help them rather than say, 'Here's a new policy, go and do it,'" Cameron told The Guardian. "We have the technology. We just need the political will to give us a fighting chance of solving this problem."