Organic agriculture promotes biodiversity

Decades of continuous land-use intensification have played a significant role in causing biodiversity to radically change. An enormous decline in biodiversity has been the result of intensive farming, introduction of foreign species, habitat change and fragmentation as well as scrub encroachment in mountainous regions. In addition, climate change is also increasingly causing changes in indigenous flora and fauna.

The endangered species Red Lists maintain that intensive farming is one of the main causes for species decline in cultivated landscapes (Bengtsson, J. et al. 2005, Hole, D.G. et al. 2005). Pesticide use, synthetic nitrogen fertilizer, land consolidation, drainage and the use of heavy machinery, have all contributed to a drastic loss of biodiversity.

Numerous comparative studies showing the impact of conventional and organic farming systems verify the positive effect organic farming has on flora and fauna on field and also farm level (Fuller, R.J. et al. 2005, Hole, D.G. et al. 2005). A comprehensive analysis of 66 scientific studies shows that organically farmed areas have on average 30 percent more species and 50 percent more individuals than non-organic areas (Bengtsson, J. et al. 2005). The positive effect of organic farming is most significant in cleared landscapes, but is also seen in structurally rich regions (Gabriel, D. et al. 2006, Gabriel, D. et al. 2010).

In particular birds, predatory insects, spiders, soil dwelling organisms and field flora benefit most from organic management (Figure 1). Pests and indifferent organisms on the other hand occur in similar numbers in the various farming systems. The differences in species diversity are especially noticeable
with arable and horticulture crops in valleys – the differences seen in grassland are less pronounced. Comparison studies in mountainous regions are scarcely existing.

To preserve rare and endangered species, adapted species protection programmes are frequently necessary. The typical ecological compensation programmes for farmland are not sufficient. Organic farming in combination with valuable semi-natural areas can therefore significantly contribute to improving species numbers (Pfiffner, L. et al. 2003). Sky larks, a typical species that have been suppressed through intensification of farming, as well as the now rare lapwings, partridges, and whinchats, achieve higher population densities on organically managed farms (NABU 2004, Neumann, H. et al. 2007). Rare plant species on agricultural land (Gabriel, D. et al. 2006, Gabriel, D. et al. 2007) and ground beetles (Pfiffner, L. et al. 2003) are also proven to be in higher diversity and density on organic farms.

Next to farming intensity, the proportion of seminatural areas on the farm is a central factor for preserving biodiversity. Hedges, species and structurally rich meadows, and scrub, serve as habitat and as a temporary retreat vital for many animal species.

Comparisons in Switzerland (Schader, C. et al. 2008) and England (Gibson, R. H. et al. 2007) show, that the proportion of semi-natural areas on organic farms is higher than on conventional farms. An analysis of all Swiss farms showed that on average organic farms have 22 percent semi-natural areas and conventional farms 13 percent. Organic farms therefore implement 2/3 more measures than their conventional counterparts (Figure 2). The largest differences were seen with extensive and less intensively used meadows as well as hedges, and standard fruit trees in lowlands and hilly regions (Schader, C. et al. 2008).

Biodiversity is an important basis for many processes in our ecosystems to function. Habitats with numerous species are shown to better adapt to environmental changes. For instance, species rich mountain meadows erode less and allow for more stable yields during dry periods.

Critical ecological processes are influenced by the higher biodiversity and larger population densities of various species seen on organic farms. Organic farming shows significant improvements for functions such as:

• Pollination (Gabriel, D. et al. 2007, Holzschuh, A. et al. 2007, Holzschuh, A., et al. 2008, Moradin, L.A. et al. 2005)
• Reduction in soil erosion on arable land (Siegrist, S. et al. 1998)
• Decomposition of dung in pastures (Hutton, S.A. et al. 2003)
• Natural pest reduction in soil (Klingen, I. et al. 2002) and crops (Crowder, D.W. et al. 2010, Zehnder, G. et al. 2007)

Flower-visiting insects such as honeybees, wild bees, and bumblebees benefit from the higher coverage and diversity of secondary flora in organic grain fields. Biodiversity is 3 times higher and the number of bees 7 times higher than in conventional areas (Holzschuh, A. et al. 2007). With organic farming areas increasing, populations of wild bees, honeybees, and bumblebees are also markedly climbing in the surrounding farmland and semi-natural areas (Holzschuh, A. et al. 2008). Organic agriculture thus improves the pollination of flowering plants in the surrounding environment (Gabriel, D. et al. 2007).

The higher diversity of flora and fauna also encourages beneficial organisms that naturally reduce pests (Zehnder, G. et al. 2007). Organic farming leads to a significantly more balanced number of beneficial insects that reduce pests and yield losses in potato crops (Crowder, D.W. et al. 2010). Organic pastures allow richer fauna to exist in dung than conventional pastures as they are not contaminated by chemical veterinary drugs (Holzschuh, A. et al. 2007). Dung fauna considerably adds to the degradation and recycling of dung and in turn makes for better feed quality.

A more diverse flora and fauna in organic soil result in a revitalized, more active soil life (Mäder, P. et al. 2002). Research from Norway shows a stronger reduction in soil pests in organic soils than in conventional soils due to richer fungal fauna (Klingen, I. et al. 2002).

Various farm practices and landscaping measures are implemented in organic farming that have a proven positive influence on biodiversity. The following
measures typically carried out on organic farms that most notably promote biodiversity are:

• Forgo use of herbicides
• Forgo use of chemically-synthesized pesticides
• Less and purer organic fertilizer
• Fewer cattle per square meter
• More diversified crop rotation with higher clovergrass percentage
• Conservation tillage
• Higher percentage of semi-natural areas
• Higher percentage of arable and ecological areas
• More diversified farm structure

These factors enhance not only biodiversity, but strengthen natural cycles and improve environmental performance that in turn increase the sustainability of organic farms (FAO, 2002, Pimentel, D. et al. 2005). To optimally promote biodiversity, cross-farm and landscaping measures need to be instituted – ideally on extensively managed habitats within landscapes (e.g., bioregions) (Gabriel, D. et al. 2010).