Long-term effects of conversion to organic farming on ecosystem services - a model simulation case study and on-farm case study in Denmark

ABSTRACT

Organic agriculture aims to produce food while establishing an ecological balance to augment ecosystem services (ES) and has been rapidly expanding in the world since the 1980s. Recently, however, in several European countries, including Denmark, organic farmers have converted back to conventional farming. Hence, understanding how agricultural ES are affected by the number of years since conversion to organic farming is imperative for policy makers to guide future agricultural policy. In order to investigate the long-term effects of conversion to organic farming on ES we performed i) a model simulation case study by applying the Daisy model to simulate 14 different conversion scenarios for a Danish farm during a 65 year period with increasing number of years under organic farming, and ii) an on-farm case study in Denmark with one conventional farm, one organic farm under conversion, and three organic farms converted 10, 15 and 58 years ago, respectively. Both the model simulation case study and the on-farm case study showed that non-marketable ES values increased with increasing number of years under organic farming. Trade-offs between marketable and non-marketable ES were not evident, since also marketable ES values generally showed an increasing trend, except when the price difference between organic and conventional products in the model simulation study was the smallest, and when an alfalfa pre-crop in the on-farm case study resulted in a significantly higher level of plant available nitrogen, which boosted the yield and the associated marketable ES of the subsequent winter rye crop. These results indicate a possible benefit of preserving long-term organic farms and could be used to argue for agricultural policy interventions to offset further reduction in the number of organic farms or the land area under organic farming.

KEYWORDS:

• Long-term
• conversion
• economic value
• ecosystem services
• organic farming
• agricultural policy
• trade-offs

Acknowledgments

This work was funded by the ‘MACSUR-FACCE’ and co-supported by the China Scholarship Council. The authors would like to thank agricultural consultant Lisbeth Frank Hansen for assistance in finding the study sites, famers Jesper Skovgaard Shiønning, Ulrik Salomonsen, Henrik Petersen and Mogens Nordgaard Christensen for their support and permission to take field samples, as well as technical staff at the University of Copenhagen. This work would not have been possible without their assistance. Thanks also to Inez Estelle Harker-Schuch and Victoria Jae Chuang for assisting in improving the language, to Per Abrahamsen for guidance of Daisy model and to Gabriela Alandia for her comments on the manuscript.