“Green algae, mega-basins: two symptoms of the ecological emergency that call for inventing the agricultural transition together”

Ihe nitrates and green algae that are deposited every summer on the coasts of Brittany are the mirror of a political choice that has generated, since the 1960s, a model of intensive agriculture very largely oriented towards animal production. The significant flows of nitrate linked to agricultural practices in all the Breton catchment areas result in massive strandings of algae, mainly present in eight bays with a particular coastal configuration. Intensive agriculture is not sustainable.

In addition to nitrate and phytosanitary pollution, it is a major emitter of greenhouse gases and contributes to the collapse of biodiversity and soil degradation. The launch at the end of 2022 of a third interministerial plan for green algae by the State and the Brittany Region is an opportunity to question the usefulness of these plans, and above all to imagine a real project for the territory and the transformation of channels.

Launched in 2011, the first action plan against green algae (PLAV) expresses the political will to eradicate green algae by 2027, which implies, according to scientists, that the concentration of nitrate in rivers reaches below 10 miilligrams per litre.

Statement of failure

In reality, the PLAV2, made public in 2017, will have the same objective as the PLAV1 of 2011, that is to say a reduction of approximately 30% of the concentrations. The future third plan, currently under negotiation, aims for a reduction of around 20% in concentrations, according to our calculations. In the context of the evolution of concentrations which has shown a stabilization for several years, this objective is very close to that of PLAV 1 and far from the initial objective of eradication, which sounds like an acknowledgment of failure, even an admission. helplessness.

The parallel with the case of the Poitevine basins is striking: faced with an unavoidable environmental constraint (the sensitivity of the coast, the scarcity of water resources), the implementation of solutions based solely on sobriety and technology hampers the possibilities of transformations deeper and more sustainable. In Brittany as in Poitou, reducing the share of agricultural land devoted to animal feed, and therefore the volume of animal production as well as the excessively high animal densities concentrated in small areas, is one of the essential changes.

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For several decades, scientists have been warning about the collapse of biodiversity and the impact of climate change, which condemns the principle of mega-basins and a large part of the methods of intensive agriculture, which the government and part of the sector agricultural prefer to ignore.

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