The miracle of our age is the conquest of hunger. In 1950, half of all human beings were malnourished. Today, in defiance of all the gloomy prognostications that I grew up with in the 1970s, and despite a vast increase in the world's population, that figure has fallen to 11%.

What enabled this marvel? The mechanisation of farming and, even more, the introduction of chemical fertilisers and pesticides. It's true that there is a downside: nitrate-based fertilisers make everything grow, not just crops, and when washed into the oceans, cause algae to bloom, contributing to oxygen depletion; some pesticides harm more than just weeds.

But here's the good news: advances in technology are solving these problems. Most arable farmers – and, indeed, many gardeners – now use a weed-killer called glyphosate, which reduces the need for nitrates. Uniquely, glyphosate can distinguish between different species of grass, attacking weeds but not cereals. As a result, yield of winter wheat and barley in the UK has increased by 12% without soil depletion. British farmers are delighted (insofar as they ever admit to being delighted about anything).

Astonishingly, though, the EU is now threatening to ban glyphosate. Its licence, whose renewal was thought to be a formality, has been extended only provisionally, which green groups around Europe have taken as their cue to lobby for an outright prohibition. Their argument is that glyphosate might cause cancer – a contention denied by the World Health Organization and the Food and Agriculture Organisation.

Of course, the idea that glyphosate might be carcinogenic is alarming. But all sorts of things might be carcinogenic in the sense of increasing your exposure to cancer to a trivial degree: drinking coffee, eating meat, filling your car, going for a walk on a sunny day. The director of the European Food Safety Authority argues that "glyphosate's carcinogenicity, if it exists at all, is seen at such levels that you would need to eat the food of 20,000 people every day in order to reach it".

Cognitive bias is a funny thing. I've noticed that the people who are most shrill in their defence of "the scientific consensus" when it comes to climate change are often quick to deny "the scientific consensus" on, say, genetic modification or fracking. If you have an instinctive dislike of modern agricultural methods, and by extension of the market economies they make possible, you will find something to hang your doubts on. The trouble is that these obscurantist fears are infecting the Brussels institutions, creating a real possibility that the EU will, as it has with neonicotinoids and GM, decree another irrational ban.

There is scant chance of the United Kingdom following suit. No mainstream British politician, to my knowledge, is proposing anything so self-harming as a glyphosate ban.

So what will happen if, following Brexit, the EU outlaws glyphosate and the UK doesn't? Will the EU be able to close its markets to British wheat and barley? Not unless it closes its markets to the entire world, since no other country is seriously contemplating a glyphosate ban. Which means that British farmers might find themselves picking up the slack as production in the EU declines.

Similar considerations apply to other sectors. When the EU decrees some pointless restriction, Britain could benefit simply by standing aside, as Switzerland did when the EU began to regulate fund-management. At worst, we will face a choice between copying the new rules for the sake of easier exports to the Continent or disregarding them and concentrating on world markets. Which choice we take will vary by sector and by circumstance; but having a choice at all will be a huge improvement on where we are now.

There's a popular refrain among half-clever Remainers that goes something like this. "So, Leavers, you've got your way. Now that we can scrap all these supposedly onerous Brussels rules, which ones do you want to get rid of? Name just five – if you can!"

The challenge isn't to name five; it's to pick which five to start with. I'd go for the "Droit de Suite" rules which have done huge harm to London's art market; the Alternative Investment Fund Managers Directive, which has driven a lot of business to Switzerland and Asia; the Temporary Workers' Directive, which seriously damages our temping agencies; the REACH directive, that penalises our chemicals sector; and the rules that push up energy prices. Other irritants – the Waste Electronic and Electrical Equipment Directive, the End of Life Vehicles Directive, the restrictions on herbal medicines – can wait their turn.

The glyphosate saga, though, reminds us that the EU is constantly generating new regulations. The benefit of Brexit is not simply the ability to undo past rules – rules which businesses moaned about, but have since adapted to. Rather, it is the exemption from future ones, several of which are already in the pipeline – for example, the Ports Services Directive, which was opposed by every UK port operator, trade union and MEP, but approved anyway.

Brexit, in short, will be a process rather than an event. The day after we leave will look very like the day before. That's the day that we can begin to pursue a different trajectory, disapplying rules that were designed with others in mind, reorienting to world markets.

The benefits will be cumulative rather than instant. It took a full decade before everyone realised that it would have been disastrous to have joined the euro. Give it another decade, and the only question people will ask is why we didn't leave sooner.

Daniel Hannan has been Conservative MEP for the South East of England since 1999, and is Secretary-General of the Alliance of European Conservatives and Reformists.