The Japanese, like other nations, have long placed food and farming at the heart of their traditional culture. They have long regarded rice, especially, with a semi-mystical reverence, performing a whole series of seasonal rituals to honour and propitiate local rice deities to ensure an abundant crop.

Over the last 70 years or so, farming hasn’t loomed large only in the Japanese psyche. Farmers have also played a disproportionately powerful role in Japanese politics. In an economy that has long been fiercely protective of many domestic industries, few have been quite so shielded from foreign competition as the local agricultural sector.

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However, the power of Japan’s farming lobby is now waning, and the consequences of its decline promise to reshape international relations across Asia and beyond.

For many years following the second world war, the Japanese government slapped prohibitive tariffs on foreign foods. It also erected formidable, and often insurmountable, non-tariff barriers against food imports. For example, for decades Tokyo operated strict standards on the size, shape and colouring of fruit, vegetables and other foodstuffs. In one notorious case, Japanese regulators even decreed the maximum permitted degree of curvature for cucumbers to deter cheap imports.

Even when the government began to relax explicit rules intended to block imports, cultural and political opposition to foreign foods remained deeply entrenched. For example, when in the early 2000s railway company JR East attempted to sell “bento” lunchboxes containing rice from California, the Ministry of Agriculture denounced its move as “deplorable”.

The disproportionate political power enjoyed by Japan’s farming lobby dates back to the sweeping land reforms instituted in the immediate aftermath of the second world war. Before the war, most farmland had been owned by a dominant landlord class. Rather than trying to raise output, they simply concentrated on extracting rent from the tenant farmers who worked the land. Meanwhile, tenant farmers, burdened by high rents, lacked the means to invest in improving productivity. Trampling over property rights, the post-war government redistributed land ownership equally to all farming families.

This encouraged the sort of small-scale, highly intensive agriculture which best made use of the available resources, pushing up both crop yields and rural incomes. The shift boosted demand and paved the way for increased migration to the cities, underpinning Japan’s rapid post-war economic development.

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The mass of Japan’s farmers profited mightily. In return they pledged their loyalty to the dominant Liberal Democratic Party, which reciprocated by ensuring continued political protection for their livelihood.

So things stayed. Meanwhile, the world – and Japan – changed. For one thing, Japan’s farmers got old, and the younger generation has shown little interest in agriculture. Today the average age of a Japanese farmer is 67. Many have died or quit the land, leaving an area the size of Taiwan untilled. And of those still in business, a large number concentrate on producing showpiece fruit and vegetables from postage stamp-sized plots.

Giant strawberries, grapes the size of golf balls and square melons might command sky-high prices in the high-end supermarkets of Hong Kong and Southeast Asia. But they cannot feed Japan’s population.

In consequence, Japan has become ever more reliant on imports to meet its basic food needs. The trend has been compounded by changing dietary habits. A recent straw poll of students found that only about half eat a traditional Japanese breakfast of rice, fish and miso soup. The rest preferred foreign foodstuffs like granola and yogurt or bread.

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This shift has led Japan’s per capita consumption of rice to fall by more than half over the past 50 years, while the consumption of meat – especially beef – dairy products, bread and pasta has soared.

The problem is the wheat needed for bread and pasta does not grow in Japan, while domestic dairy and meat production has failed to keep pace with demand. As a result, Japan today produces domestically just 38 per cent of the food calories it consumes, the lowest self-sufficiency rate of any developed economy.

This increasing dependence on imported food is making Japan’s ruling politicians feel vulnerable. Their response has been to turn their backs on the decades-old relationship that protected the country’s farmers. Instead, they are vigorously pursuing free trade agreements around Asia and the wider world in the hope of locking in reliable supplies of affordable food imports for the future.

Traditionally, Japan has imposed tariffs as high as 40-50 per cent on imported foodstuffs such as beef. Now, however, Tokyo’s negotiators are touting access to the vast Japanese domestic market – the world’s third-largest economy – at tariffs of 10 per cent or lower on staple food imports as an incentive to other countries to sign bilateral or multilateral trade deals.

This political about-turn has had far-reaching effects. It was Japanese diplomacy that kept alive Barack Obama’s Trans-Pacific Partnership after US President Donald Trump announced America’s withdrawal from the trade deal in January. Now, thanks to Tokyo’s efforts, the remaining 11 TPP economies – a bloc with collective US$11 trillion GDP, equal to China’s – are expected to sign off on a final deal in November.

Nor is Tokyo’s enthusiasm for freer trade limited to the Asia-Pacific. In July, Japan secured an agreement in principle for a trade pact with the European Union. Last month Japanese officials held informal talks about a post-Brexit trade deal with British Prime Minister Theresa May. And this month Japan is expected to begin negotiations with the US for a future bilateral trade agreement. In short, mounting food insecurity and the political decline of Japan’s traditionally powerful farming lobby – alongside insecurity over the economic and military rise of China – accounts for Tokyo’s emergence in recent months as the world’s leading champion of global and regional free trade deals. How times – and cultures – change.

Tom Holland is a former SCMP staffer, who has been writing about Asian affairs for more than 20 years