Until a couple of weeks ago, the idea of waiting in an Ocado queue of 73,735 shoppers, or of supermarkets rationing milk and baked beans, would have sounded like satire. For too many people in the UK, food scarcity is the norm, with mothers and fathers going hungry to ensure their children are fed. But others have grown used to an absurd abundance: strawberries and peaches in midwinter, or 20 types of mustard alongside three score of pasta. When such bounty overflows, it seems self-evident that supplies are both plentiful and reliable – until suddenly they aren’t.

In fact, warns Tim Lang in his new book, Feeding Britain, our food system is “stretched, open to disruption and far from resilient”. It is easy to castigate panic buyers for empty shelves. But while shopping responsibly will help others to get the food they need, only a few people are squirrelling away vast stocks. Research firm Kantar says the average spend per supermarket trip has risen by 16% to £22.13 month on month – not surprising when households realised they were likely to need lunches at home, including for children no longer in school, and could have to self-isolate for a fortnight.

The underlying problem is that just-in-time supply chains can struggle to cope with even relatively small shifts, and that a handful of retailers dominate the market. The top eight account for more than 90% of all grocery sales in Britain, with Tesco alone accounting for 27%. The efficiencies that have kept food prices low, and the long and complex global chains that bring us such variety, come at a price.

Border closures due to the virus as well as sickness could yet hit agriculture and delivery. Farmers say they face huge labour shortages, though Britain, France and others are discussing new “land armies” to bring in crops normally harvested by migrant workers. Some countries are imposing limits on exports of staples to ensure they can feed their own populations. Only half the food we consume in Britain is produced here.

The hardest hit will be those who suffer at the best of times. Food charities have warned that millions will need food aid in the coming days. The government says military planners are organising a food delivery system for the 1.5 million people most vulnerable to coronavirus, and is developing a scheme to support the 1.6 million children who rely on free school meals – probably in the form of supermarket vouchers.

This reliance on big retailers is shortsighted. While officials consult with business bosses, local authorities such as Newham in London have the information, experience and resources to reach people in need, but say they cannot get the cash they require. Other efforts, both commercial and social, need support, like the independent shops (in many cases still well stocked) which are launching local delivery services, or the restaurants offering to help feed the isolated.

Relying on market forces has created many of the problems we now face. The pandemic is exposing our food system’s fragility: a crucial warning in a world where other shocks – notably from climate change – will be heading our way. In a time of crisis, we must adapt fast. But there are still choices. This could be an opportunity to diversify our supply chain, promote sustainable agriculture, benefit local businesses and find new ways of serving communities. If it instead entrenches the hold of the supermarket giants it will not only be a missed opportunity, but will also leave us in a more precarious position to face the next crisis.