May Buzz Builder:

Does Organic Farming Increase Biodiversity?

The significant body of scientific knowledge on this question shows that when organic farms include a diversity of crops and non-crop areas, when synthetic pesticides are replaced with natural pest management systems, when nutrients are added using biological sources such as compost (animal manure and increasingly municipal manures) instead of synthetic fertilizers, then organic systems almost always score higher for biodiversity than conventional farming. Therefore, the short answer to the question posed in the title is “yes”.
Using data from Europe, New Zealand, USA and Canada, Hole et al. (2005) stated that “The majority of the 76 studies reviewed in this paper clearly demonstrate that species abundance and/or richness, across a wide-range of taxa, tend to be higher on organic farms than on locally representative conventional farms.” 

A major driver of improved biodiversity on organic farms is greater plant diversity.  Higher floral diversity in organic fields increased host plants for larvae and adult nectar resources for flower-visiting insects, resulting in more butterflies and bumblebees, for example.  Elimination of pesticides, especially insecticides, also plays a large role in restoring biodiversity.

I want to emphasize plant diversity, not only because I am a professor in a Plant Science department, but because plant diversity is something that farmers can control.  Therefore, by managing plant diversity, farmers can increase the diversity of other organisms.  It is also important to recognize that “greater floral diversity” does not have to mean more weeds in organic fields.  Organic farmers can increase plant diversity by growing grain mixtures such as oats and peas, lentils and flax, and they can include flowering cover crops such as red clover in their cropping systems.  Therefore, “greater floral diversity” can produce both biodiversity and economic benefits.
The “Jena” project is located in central Germany and has allowed scientist to test the plant diversity-biodiversity theory in a grassland context.  Results show that as plant diversity increases, so does above and below ground biodiversity.  Examples of above ground biodiversity included flower visits by insects and activity of parasitic wasps, while below ground processes included beneficial nematodes and mycorrhizal fungi (Scherber et al. 2010). 
Plant diversity increases in the Jena project also coincided with more carbon capture in soils (Lange et al. 2015), a major goal in mitigating climate change.  Similar results for soil carbon have been observed at the University of Manitoba’s Glenlea long-term organic plots.  Our Glenlea work shows that as plant diversity in the organic systems is increased, the amount of living soil carbon (microbial biomass carbon) also increases (Braman et al. 2016). We attribute higher levels of living carbon in the organic systems at Glenlea to greater plant and soil biodiversity.

Now that we know organic farming systems can result in greater biodiversity, a new question becomes “How do we best deploy organic farming on the landscape for maximum biodiversity benefit?”  In other words, given that we are experiencing serious biodiversity decline, how do we best use the 2% of organically managed land in Canada to maximize effect?  Another way to consider this question is “Where should governments and consumers invest in organic agricultural production systems for the most biodiversity benefit?”
This question has been studied by a team of Swedish agroecologists led by Henrik Smith.  One of their studies showed that in order to restore farmland biodiversity, organic farming was most efficient in monoculture landscapes where there were only a few crop types and few natural areas (Smith et al. 2010).  If I could apply their results to my home province, the results suggest it is better to plop an organic farm in the middle of an intensive agricultural region like the Red River Valley (Figure 1) than in the more diverse landscape of western Manitoba (Figure 2), for example.  
Of course, organic farms play an important biodiversity conservation role in both landscapes, but I can understand the logic of giving nature a break from monoculture and pesticides, and comparing these two regions of Manitoba, such a break is most needed in the Red River Valley.  The Swedish study stated that one of the mechanisms for a positive diversity effect was that organic fields and farms acted as hotspots, which allow organisms born and bred in the organic fields to spill over into adjacent conventional fields.

Canadian governments and agricultural producer groups have discussed biodiversity schemes for years, and they have developed a long list of “best management practices” or “BMPs”.  It has been frustrating to watch organic farming be excluded from these BMP lists.  This must stop.  It is time that organic farming be recognized as one of the best BMPs for restoring farmland biodiversity in Canada.
About Martin Entz:

Martin Entz in the Faculty of Agricultural and Food Sciences at the University of Manitoba works on sustainable agricultural systems.

Together with fellow researchers, students, technicians, farmers, and interested citizens, Martin has involved Canadian organic farmers directly in the development of crop varieties for organic production in partnership with USC Canada and Agriculture and AgriFood Canada. 

Martin is part of Sustainable Canada Dialogues, a group of 60 Canadian scholars who propose evidence-based climate solutions and actions.
 
References

Braman, S., Tenuta, M. and Entz, M.H., 2016. Selected soil biological parameters measured in the 19th year of a long term organic-conventional comparison study in Canada. Agriculture, Ecosystems & Environment, 233, pp.343-351.

Hole, D.G., Perkins, A.J., Wilson, J.D., Alexander, I.H., Grice, P.V. and Evans, A.D., 2005. Does organic farming benefit biodiversity?. Biological conservation, 122(1), pp.113-130.

Lange, M., Eisenhauer, N., Sierra, C.A., Bessler, H., Engels, C., Griffiths, R.I., Mellado-VĂĄzquez, P.G., Malik, A.A., Roy, J., Scheu, S. and Steinbeiss, S., 2015. Plant diversity increases soil microbial activity and soil carbon storage. Nature communications, 6(1), pp.1-8.

Scherber, C., Eisenhauer, N., Weisser, W.W., Schmid, B., Voigt, W., Fischer, M., Schulze, E.D., Roscher, C., Weigelt, A., Allan, E. and Beßler, H., 2010. Bottom-up effects of plant diversity on multitrophic interactions in a biodiversity experiment. Nature, 468(7323), pp.553-556.

Smith, H.G., DĂ€nhardt, J., Lindström, Å. and Rundlöf, M., 2010. Consequences of organic farming and landscape heterogeneity for species richness and abundance of farmland birds. Oecologia, 162(4), pp.1071-1079.
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