Do European agroforestry systems enhance biodiversity and ecosystem services? A meta-analysis

Abstract

Agroforestry has been proposed as a sustainable agricultural system over conventional agriculture and forestry, conserving biodiversity and enhancing ecosystem service provision while not compromising productivity. However, the available evidence for the societal benefits of agroforestry is fragmented and does often not integrate diverse ecosystem services into the assessment. To upscale existing case-study insights to the European level, we conducted a meta-analysis on the effects of agroforestry on ecosystem service provision and on biodiversity levels. From 53 publications we extracted a total of 365 comparisons that were selected for the meta-analysis. Results revealed an overall positive effect of agroforestry (effect size=0.454, p<0.01) over conventional agriculture and forestry. However, results were heterogeneous, with differences among the types of agroforestry practices and ecosystem services assessed. Erosion control, biodiversity, and soil fertility are enhanced by agroforestry while there is no clear effect on provisioning services. The effect of agroforestry on biomass production is negative. Comparisons between agroforestry types and reference land-uses showed that both silvopastoral and silvoarable systems increase ecosystem service provision and biodiversity, especially when compared with forestry land. Mediterranean tree plantation systems should be especially targeted as soil erosion could be highly reduced while soil fertility increased. We conclude that agroforestry can enhance biodiversity and ecosystem service provision relative to conventional agriculture and forestry in Europe and could be a strategically beneficial land use in rural planning if its inherent complexity is considered in policy measures.

Spatial diversification of agroecosystems to enhance biological control and other regulating services: An agroecological perspective

“…Intercropping that provides benefits towards pest control can also lead to an increase of nitrogen and carbon in soils when leguminous plants are combined with cereals, potentially favouring soil fertility and reducing nutrient run-off with fewer fertilizer applications (Bedoussac et al, 2015;Cong et al, 2014). As for agroforestry systems, a recent meta-analysis shows that the introduction of trees generally reduces soil erosion, increases soil fertility and nutrient cycling as well as biodiversity (but the type of biodiversity, hence the functions it can exert, was not specified) (Torralba et al, 2016). The presence of trees within fields would also create a microclimate with potential benefits, but also deficits for ecosystem functioning.…”

Exploring the potential of edible forest gardens: experiences from a participatory action research project in Sweden

“…Meta-analyses from temperate areas present compelling evidence that an increase in the complexity in the agricultural landscape through agroforestry systems delivers more supporting and regulating ecosystem services, such as carbon sequestration, maintenance of biodiversity, water quality, nutrient recycling, soil fertility and erosion, than conventional land use (Tsonkova et al 2012;Kim et al 2016;Torralba et al 2016;Wilson and Lovell 2016).…”

“…Agroforestry may be a feasible option. Current research shows that such systems are both productive and generate more ecosystem services than conventional land use in tropical and temperate areas (Pretty et al 2006;Jose 2009;Torralba et al 2016;Wilson and Lovell 2016).…”

“…However, for the systems to be efficient carbon sinks, they must be composed mainly of perennial crops, while this potential is substantially less when perennials are intercropped in systems dominated by annuals (Alam et al 2014;Torralba et al 2016). Moreover, the key design components for high conservational values in agroforestry have been found to be the inclusion of multiple species and vegetative strata, minimal management intensity and long rotation periods (Jose 2012).…”

“…Most experience and knowledge about modern agroforestry has originated from tropical areas (Torralba et al 2016), where it is a way to increase the production of necessary products when land is a scarce resource (Smith et al 2012a). However, agroforestry in temperate areas has been a tradition since ancient times.…”