Unless there is a major hiccup in the next few days, an incredibly powerful company will shortly be given a licence to dominate world farming. Following a nod from Donald Trump, powerful lobbying in Europe and a lot of political arm-twisting on several continents, the path has been cleared for Monsanto, the world’s largest seed company, to be taken over by Bayer, the second-largest pesticide group, for an estimated $66bn (£50bn).

The merger has been called both a “marriage made in hell” and “an important development for food security”. Through its many subsidiary companies and research arms, Bayer-Monsanto will have an indirect impact on every consumer and a direct one on most farmers in Britain, the EU and the US. It will effectively control nearly 60% of the world’s supply of proprietary seeds, 70% of the chemicals and pesticides used to grow food, and most of the world’s GM crop genetic traits, as well as much of the data about what farmers grow where, and the yields they get.

It will be able to influence what and how most of the world’s food is grown, affecting the price and the method it is grown by. But the takeover is just the last of a trio of huge seed and pesticide company mergers. Backed by governments, and enabled by world trade rules and intellectual property laws, Bayer-Monsanto, Dow-DuPont and ChemChina-Syngenta have been allowed to control much of the world’s supply of seeds. You might think that these mergers would alert the government, but because political parties in Britain are so inward-looking, and because most farmers in rich countries already buy their seeds from the multinationals, opposition has barely been heard.

Instead, it is coming from the likes of Debal Deb, an Indian plant researcher who grows forgotten crops and is the antithesis of Bayer and Monsanto. While they concentrate on developing a small number of blockbuster staple crops, Deb grows as many crops as he can and gives the seeds away.

This year he is cultivating an astonishing 1,340 traditional varieties of Indian “folk” rice on land donated to him in West Bengal. More than 7,000 farmers in six states will be given the seeds, on the condition that they also grow them and give some away.

This seed-sharing of “landraces”, or local varieties, is not philanthropy but the extension of an age-old system of mutualised farming that has provided social stability and dietary diversity for millions of people. By continually selecting, crossbreeding and then exchanging their seeds, farmers have developed varieties for their aroma, taste, colour, medicinal properties and resistance to pests, drought and flood.

Deb’s community seed bank is one of the last living repositories of hundreds of Indian rice varieties. It is also an act of ecological and political defiance against the immense reach and concentration of the likes of Monsanto and Bayer.

The corporates argue that only consolidation can bring the development of better seed varieties and the innovations needed to avert global hunger and malnutrition, as the world population climbs to around 10 billion people in a few decades’ time.

By innovation, they mean new, “advanced” plant engineering technologies such as GM, Crispr, gene editing and bio-fortification. History, however, suggests strongly that the reality will be the opposite. It is far more likely, say environmentalists and farm groups in developing countries, that competition will be limited and that the legal and biological grip of seed corporates on global farming will tighten. The small farmer, who has traditionally fed the world and given societies their rich food cultures, will only be threatened further.

A farmer walks across a field of organic crops in Lower Nandok, Sikkim, India. Photograph: Bloomberg/Getty Images

Forty years ago, farmers and consumer groups might have welcomed potential opportunities offered by agri-science and large corporate mergers. But today, there is no sense of agri-optimism. Yields of most staple crops have barely increased in years, seeds and herbicides are becoming more expensive, and the promised health, safety and nutritional benefits of new industrial crops have failed to materialise.

Instead, farm pollution increases, agricultural biodiversity continues to be lost and nearly 30 years and many billions of dollars of R&D after Monsanto breezed into Europe pledging to feed the world, there are still around 800 million people who are malnourished, no public enthusiasm for industrial farming, and open cynicism about corporate motives.

The UK and US governments, together with a few major agri-philanthropists such as the Gates Foundation, still plough billions of dollars a year into hi-tech, high-input farming, but the tide may be turning as simpler, grassroots solutions are being developed.

Nearly 10 million of the poorest farmers now use the system of rice intensification (SRI), which has been proven to increase rice, wheat, potato and other yields dramatically by stimulating the roots of crops. Agro-forestry techniques that grow trees and shrubs among crops is proving more productive, as is land restoration. Farmers’ groups in India and across Latin America are developing their own seed companies in order to avoid the new corporate monopolies.

If they fail, the future of food appears to be in the hands of three giant companies that are wedded to genetic modification of one sort or another. The corporates might say that isn’t a problem. Bayer’s chairman, Werner Baumann, has recently promised to “strengthen its commitment in the area of sustainability,” adding: “Agriculture is too important to allow ideological differences to bring progress to a standstill.”

But still, blinded by the prospect of new technologies, governments and research organisations have paid little attention to farmers’ traditional knowledge. They are missing out on this vast storehouse, which will be needed if the world is to adapt to climate change and population growth. Debal Deb, who lives on a shoestring and relies on friends for minimal funding to conduct his own research, has published research into rice varieties capable of growing in 12ft of water, others that can grow in 4-5ft of water, and dozens that are drought-tolerant, as well as many varieties that can grow in brackish water.

Some are said to be far richer in nutrients such as iron, zinc, magnesium, omega 3 and riboflavin than anything that the giant seed companies have developed. But such is the lack of trust and funds, Deb keeps the exact location of his farm secret and only gives his seeds to people he respects. He claims that spies have been sent to steal his seeds and companies want to patent, suppress or claim them as their own.

Instead of working in a well-funded research institute, as might be expected of a Fulbright biotech scholar, Deb is now part of the worldwide farmers’ movement to limit corporate control and to redefine what knowledge is, and who owns it. Like many others, he has found that the best way to save traditional agricultural knowledge is to grow seeds and give them away. He believes that’s the future. Pray that he’s right.

• John Vidal is a former Guardian environment editor