Modeling environmental benefits of silvoarable agroforestry in Europe

Abstract

Increased adoption of silvoarable agroforestry (SAF) systems in Europe, by integrating trees and arable crops on the same land, could offer a range of environmental benefits compared with conventional agricultural systems. Soil erosion, nitrogen leaching, carbon sequestration and landscape biodiversity were chosen as indicators to assess a stratified random sample of 19 landscape test sites in the Mediterranean and Atlantic regions of Europe. At each site, the effect of introducing agroforestry was examined at plot-scale by simulating the growth of one of five tree species (hybrid walnut Juglans spp., wild cherry Prunus avium L., poplar Populus spp., holm oak Quercus ilex L. subsp. ilex and stone pine Pinus pinea L.) at two tree densities (50 and 113 trees ha-1) in combination with up to five crops (wheat Triticum spp., sunflower Helianthus annuus L., oilseed rape Brassica napus L., grain maize and silage maize Zea mays L.). At landscape-scale, the effect of introducing agroforestry on 10 or 50% of the agricultural area, on either the best or worst quality land, was examined. Across the 19 landscape test sites, SAF had a positive impact on the four indicators with the strongest effects when introduced on the best quality land. The computer simulations showed that SAF could significantly reduce erosion by up to 65% when combined with contouring practices at medium (> 0.5 and < 3 t ha-1 a-1) and high (> 3 t ha-1 a-1) erosion sites. Nitrogen leaching could be reduced by up to 28% in areas where leaching is currently estimated high (>100 kg N ha-1 a-1), but this was dependent on tree density. With agroforestry, predicted mean carbon sequestration through immobilization in trees, over a 60year period, ranged from 0.1 to 3.0 t C ha-1 a-1 (5 to 179 t C ha-1) depending on tree species and location. Landscape biodiversity was increased by introducing SAF by an average factor of 2.6. The implications of this potential for environmental benefits at European scale are discussed.

Soil Degradation and Soil Quality in Western Europe: Current Situation and Future Perspectives

“…Some of these low-intensity areas support agroforestry systems. In a modeling study of the environmental benefits in the Mediterranean and Atlantic regions of Europe, soil erosion and nitrogen leaching were found to be lower than in conventional cropping land, and carbon sequestration was enhanced [157]. In a review of the benefits of alley cropping systems combining agriculture and short rotation coppices by growing trees in agricultural sites in temperate Europe, these systems proved efficient for soil carbon sequestration, improving fertility, controlling erosion, storing water and regulating its quality, and increasing the overall productivity compared to conventional farming [158].…”

Alley coppice—a new system with ancient roots

“…Other environmental benefits also exist. The tree rows provide habitat for several fauna and flora species, and help protect and enhance biodiversity in arable landscapes (Palma et al 2007c). Evidence suggests that the biological control of several crop pests could potentially be achieved using silvoarable systems, but knowledge on how this can be reliably managed is lacking, and more research is needed (Smits et al 2012).…”

“…The effect of trees in alley cropping systems is also of interest environmentally (Palma et al 2007c). Trees are capable of capturing and recycling fertiliser nutrients from deeper soil horizons than crops, and this helps to improve nutrient use efficiency as well as mitigate groundwater contamination by excess nutrients (Rowe et al 1999;Allen et al 2004).…”

“…Intensive agricultural production has caused groundwater and surface water contamination through nitrogen leaching and is a major environmental problem. Agroforestry systems, and alley cropping in particular, have been identified as a means by which the nitrogen contamination of water can be reduced Palma et al 2007c). Other environmental benefits also exist.…”

Impacts of agricultural land-use changes on biodiversity in Taihu Lake Basin, China: a multi-scale cause–effect approach considering multiple land-use functions

“…Thus the total value of MSA ag either decreases (because increasing area of construction is considered as negative impact on MSA ag ) or increases (because increasing area of semi-natural elements has positive impact on MSA ag ). Regarding this aspect, estimating shares of seminatural and construction areas from aerial photographs of randomly selected sites within the agricultural land cover (Palma et al 2007) and defining ecosystem quality of the semi-natural elements (MSA sn ) and constructed elements (MSA cn ) are required. For a more precise estimation, also the impacts on connectivity of semi-natural elements need to be assessed, which depends on the spatial configuration and the distance to surrounding nature areas.…”