In the world of French farming, unrestricted and royalty-free use of seeds may soon be no more than a happy memory. For several decades seeds have been brought under the protection of plant variety certificates, which enshrine plant breeders' rights.

Resowing such seed was theoretically prohibited, but in practice it was largely tolerated in France. In future it will be strictly controlled, the ruling conservative UMP party having passed a bill to this effect in parliament last November. "Of the 5,000 or so cultivated plant varieties on sale, about 1,600 are protected by a certificate [in France]. The latter category account for 99% of the varieties grown by farmers," says Delphine Guey, of France's Inter-Professional Association for Seeds and Plants.

But until now half of all cereals were obtained from farm-saved seed, according to the National Co-ordination for the Defence of Farm-Saved Seed. In other words, illegally. The authorities seem determined to stop turning a blind eye. Agriculture minister Bruno Le Maire is categorical that such seed "can no longer be royalty-free, as is currently the case".

The recent bill transposes into French law a previously ignored 1994 European regulation on protection of plant varieties. As a result farm-saved seed, which was tolerated until now, is now legal, only provided "a fee is paid to certificate holders [seed companies] to sustain funding of research and efforts to improve genetic resources". Small farmers producing less than 92 tonnes of cereal are exempted.

Soft wheat is the onlytype on which duty has been levied in France since 2001. This "compulsory voluntary contribution" is paid to the federation of seed manufacturers. Farmers must pay €0.50 (66 cents) a tonne when they deliver their crop. This system will be extended to 21 species, the list still not finally settled, said Xavier Beulin, the head of France's main farmers' union (FNSEA).

So "for half the crop species – soy, fruit and vegetables – it is forbidden to use your own seeds, and the other half – cereals and fodder – you have to pay to sow", said Guy Kastler, the head of the Semences Paysannes network and a member of the Peasant Confederation.

Several groups of ecologists and small farmers have expressed concerns at seed manufacturers' increasing control over access to seed, due to property rights being extended to crops and the resulting seed. With the new tax, "even farmers who make no use of commercial seed will have to pay for what they use", said Kastler. He is afraid that the share of farm-saved seed will decline as it becomes more expensive and consequently less attractive to farmers.

With the tax and the ban on sowing their own seed, there is a growing incentive for farmers to buy, rather than produce, seed. This worsens concern about increasing dependence on seed manufacturers.

Beulin, on the other hand, maintains that there is good reason for everyone to contribute to research into crop species, because even farm-saved seed is generally derived from company-bred varieties in the first place. Drawing a parallel with legislation to protect the digital rights of creators of music and film, he suggested that "it is only right for [users of farm-saved seed] to pay their share of funding the creation of new varieties, from which they benefit". A further source of concern is the impact of the new rules on farming diversity. Certainly sowing the same variety – almost always the result of research – does not improve biodiversity, particularly as "for all the main crops, none of the varieties in use were handed down by our ancestors; they were all obtained by selection of new varieties", Beulin said.

Kastler said that replanting your own seeds could lead to variations in a species, thus favouring biodiversity. "New characteristics appear so the plant is better suited to the soil, climate and local conditions. This means there is less need for fertilisers and pesticides. Conversely seed companies adapt plants to suit fertilisers and pesticides, which are the same everywhere," he said. France's plant variety certificates are an alternative to patents on living things, as enforced by the United States. This intellectual property right is held by companies that have developed cultivated species through research, and consequently enjoy a monopoly over sales of the corresponding seed, until such time as it comes into the public domain. Some in the industry, including Kastler, are afraid of gradual slippage towards this patent-based regime, by limiting the right of farmers to use protected seed freely.

However, unlike plant variety certificates, patents place an absolute ban on the use of farm-saved seed, with or without the payment of fees, Guey points out. Plant variety certificates also allow plant breeders unrestricted use of a protected variety to exploit its genetic resources and select new ones. But though they may work on a gene belonging to a particular species they cannot patent it or wholly appropriate it. According to Guey this distinction has helped maintain a degree of diversity among French seed companies, and by extension gives farmers a larger choice of species. However, although France has not agreed to patents on living things, patenting of plant genes is increasingly frequent.

This article originally appeared in Le Monde