After years of insufficient yields in their orchards, blackcurrant growers and liqueur manufacturers in Burgundy-Franche-Comté contacted CNRS scientists in 2017: concerned about the future of their sector, they were looking for solutions. Specialized in pollination and interactions between species, ecologist Marie-Charlotte Anstett begins by establishing an inventory of the presence of pollinators in her plots. Luckily, the National Institute of Agricultural, Food and Environment Research (INRAE) recorded abundance data in this sector in the 1980s, and new measurements can be made in the same fields. The result is surprising: in less than 40 years, 99% of pollinators have disappeared.
“I myself did not do the manipulations in the 80s. That is why there are small errors in the numbers.explains M.me Anstett. But the order of magnitude is astonishing. And forty years ago, the measures were taken because farmers were already complaining about a drop in yields! » At the same time, the CNRS researcher installed large nets on a dozen blackcurrant plants among several farmers, under which she placed bumblebee nests. The result is once again spectacular: the yields of these plants are more than three times higher than those of the control plants.
The example of the Burgundy black currant is striking, a variety especially sensitive to the absence of pollinators. Although it only affects a few dozen farmers, it illustrates a much broader trend, although difficult to quantify: while on a global scale agricultural yields of certain crops have stagnated since the late 1990s, the loss of biodiversity could appear as one of the main explanatory factors, along with other causes, such as climate change. Intensive agriculture established after World War II led to the destruction of species and ecosystems, which in turn harmed production.
“At the limits of the system”
“Yields in France are declining, while research into varietal genetic improvement continues to produce increasingly efficient varieties.specifies Vincent Bretagnolle, director of research at the CNRS. The collapse of biodiversity causes an alteration in soil quality and a decrease in agricultural production. »
“We are reaching the limits of the chemical agriculture system, which alters all aspects of biodiversityalso states Aude Vialatte, director of research in landscape agroecology at Inrae. The boomerang effect is such that performance problems are becoming more important. » In a study published in March in the British journal Nature Ecology and Evolutionan international team of researchers talks about “escalation traps” to describe these production drops “caused by the negative feedback of biodiversity loss at high input levels”.
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