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Organic farming in vineyards does not promote biodiversity

press release of April 30, 2010

Vineyards respecting organic production rules do not host more species than those following an integrated production (IP) approach. That was the main conclusion of a study co-financed by the National Centre of Competence in Research Plant Survival, an interdisciplinary network housed at the University of Neuchâtel. The research was carried out at the University of Fribourg and has been published just now in the journal Biological Conservation.

Under the supervision of Sven Bacher, research leader at the University of Fribourg, Odile Bruggisser compared IP and organic vineyards along the banks of the lac de Bienne. The objective of her master thesis was to evaluate the ecological consequences of biological pest management as well as different conventional methods to control weeds (mulching or mowing) or insect pests (fungicides sprayed by hand or by helicopter). To do this, the young biologist measured the impact of these management methods on three trophic levels (plants, grasshoppers and spiders).

No positive influence on the abundance and diversity of these three groups of organisms was observed in the organic vineyards during this experiment. With respect to grasshoppers, their diversity was even higher in IP vineyards. The researchers explain these unexpected results: "Organic farming is often associated with high biodiversity; however, our results suggest that even though this approach is beneficial in annual crops, its effect on the diversity of species in perennial crops such as in vineyards or orchards is not so clear". 

The authors hypothesize that the impact of organic production on the diversity of organisms in perennial crops is different than that observed in annual ones such as wheat, because the general level of disturbance in perennial crops is much lower. Perennial crops are not replanted every year, hence the level of soil disturbance by cultivation is considerably lower. Vineyards offer a stable habitat for a large number of organisms over a period of around forty years. Organic production reduces the level of disturbance even further, thereby enabling the establishment of an ecological balance, where stronger competitors are favoured. Other species that are more tolerant of disturbances would prefer a conventional approach. Consequently, organic production may, under certain circumstances, lead to a reduction of biodiversity.

In annual crops, however, plants are harvested in their entirety each season. Organisms that have established themselves in these ecosystems see their habitat being regularly disturbed.  On top of that is the massive use of pesticides. An organic approach with a drastic reduction in pesticide use compensates for these disturbances and hence increases the biodiversity in these cultures.

Odile Bruggisser and her colleagues concluded that the disturbances inherent to organic vineyards may be too weak to have a significant effect on biodiversity.

contacts

Odile Bruggisser
University of Fribourg
Unit of Ecology and Evolution
Tel. : +41 26 300 88 67
odile.bruggisser@unifr.ch

Dr Sven Bacher
University of Fribourg
Unit of Ecology and Evolution
Tel. : +41 26 300 88 22
sven.bacher@unifr.ch


(c) O. Bruggisser