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María Rosa Mosquera-Losada

Mário Gabriel Santiago Santos

Berta Gonçalves

Nuria Ferreiro-Domínguez

Marina Castro

María Pilar González-Hernández

Juan Luis Fernández-Lorenzo

Jose Antonio Aldrey-Vázquez

Cristina Cabaleiro Sobrino

Jose Javier Santiago-Freijanes

• ¹Department of Crop Production and Engineering Projects, High Polytechnic School, University of Santiago de Compostela, Lugo, Spain
• ²Agroecology Innovation Advisory USC Spin-off, University of Santiago de Compostela, Lugo, Spain
• ³Laboratory of Fluvial and Terrestrial Ecology, Innovation and Development Center, University of Trás-os-Montes e Alto Douro, Vila Real, Portugal
• ⁴Laboratory of Ecology and Conservation, Federal Institute of Education, Science and Technology of Maranhão, Buriticupu, Brazil
• ⁵Department of Biology and Environment, Centre for the Research and Technology of Agro-Environment and Biological Sciences (CITAB), Institute for Innovation, Capacity Building and Sustainability of Agri-Food Production (Inov4Agro), University of Trás-os-Montes e Alto Douro, Vila Real, Portugal
• ⁶Centro de Investigação de Montanha (CIMO), Instituto Politécnico de Bragança, Campus de Santa Apolónia, Bragança, Portugal
• ⁷Laboratório Associado para a Sustentabilidade e Tecnologia em Regiões de Montanha (SusTEC), Instituto Politécnico de Bragança, Campus de Santa Apolónia, Bragança, Portugal
• ⁸Geography Department, University of Santiago de Compostela, Santiago de Compostela, Spain

Agroforestry (AF) is a sustainable land use practice and system that increases the ecosystem services delivery from agricultural lands compared with treeless systems. Agroforestry can be considered a practice when linked to plot scale (silvoarable, silvopasture, homegarden, woody linear landscape strips, and forest farming), and a system when associated with the global farm scale. The enhancement of the ecosystem services is associated with the use and promotion of the biodiversity caused by the presence of trees that optimizes the use of the resources if adequate species are mixed. Agroforestry can be implemented at temporal and spatial scales. At the temporal scale, the use of woody perennials to increase soil fertility is a traditional technique that improves soil health and reduces the need of using herbicides (e.g., the legume Ulex sown for 10 years in between crop cultivation). Five agroforestry practices can be implemented at the plot level: silvopasture, silvoarable/alley cropping, homegardens/kitchengardens, woody linear landscape strips, and forest farming. A farm including these practices is considered an agroforestry system working at the landscape level when several farms are mixed. In spite of the acknowledgment that AF has at the European level for being included as part of Pillars I and II, the spread of AF is limited across Europe. Four challenges, linked with technical, economic, educational, and policy development, have been identified by the AFINET thematic network that, if addressed, may foster policy adoption across the EU. This article proposes 15 different policy recommendations to overcome them and the need of developing an AF strategy for the EU.

1. Introduction

Europe faces the important challenge of establishing sustainable agriculture and implementing food security (Mosquera-Losada et al., 2012) while reducing negative impacts on the environment, including biodiversity loss and climate change, as declared by the Green Deal [European Union (EU), 2020a] and the Farm to Fork strategy [European Union (EU), 2020b]. Climate-smart agriculture (CSA) contributes to the achievement of global sustainable development goals [Food and Agriculture Organisation (FAO), 2022] as it integrates the three dimensions of sustainable development (economic, social, and environmental) by jointly addressing food security and climate challenges. The CSA document published by the Food and Agriculture Organisation (FAO) (2022) includes agroforestry (AF) practices as part of integrated systems to promote within the CSA framework, as was included by the European Union (Decision 529/2013/EU). The huge potential contribution of AF to CSA is linked with the possibility of being applied at the plot, farm, and/or landscape levels, depending on the spatial use and combination of agroforestry practices. In fact, the environmental impact of intensive agriculture has become increasingly negatively acknowledged [Food and Agriculture Organisation (FAO), 2022]. In this regard, modern agriculture has to combine high productivity with low impact in order to feed sustainably the growing world population, that is to say, an eco-intensification of agriculture should take place [European Union (EU), 2020a]. AF has been recognized as a sustainable land use practice and system, mixing modern and traditional practices, that is not currently acknowledged by farmers or policymakers. Therefore, the expansion of AF in Europe should consider both the main challenges highlighted by farmers to adopt AF practices and the promotion of an enabling environment (policies, funds, support, and infrastructure) from policymakers as found in the AFINET project. In the European Union, the Common Agriculture Policy (CAP) is one of the most relevant drivers for the agricultural sector, which should be used to promote AF adoption in the European continent. For the purpose of this study, agroforestry can be considered a practice when linked to plot scale (silvoarable, silvopasture, homegarden, woody linear landscape strips, and forest farming), and a system when associated with the farm scale and at the landscape level when several farms are combined. This study aims at describing the main AF practices in Europe and identifying the main challenges to AF adoption as a land management use and proposes a set of solutions from a policy perspective to favor an adequate business environment for farmers from the CAP.

2. Agroforestry: Biodiversity and ecosystem services delivery in Europe

Agroforestry (AF) is a sustainable land use practice and system recognized by the Food and Agriculture Organisation (FAO), 2015, which provides many ecosystem services and can increase sustainability in the different types of agricultural land use recognized by the CAP: arable lands, permanent grasslands, and permanent crops (woody perennials and fruit trees), as shown in Figure 1. Farmers together with policymakers and consumers are key actors to foster the implementation of AF; therefore, they should be informed (and participate in discussion forums) about the sustainability that AF provides.

Figure 1. Main components and AF benefits for arable, permanent grassland, and permanent crop lands paid by the EU direct payments. OM, organic matter.

2.1. Biodiversity

Regarding the important role of AF on biodiversity, several reports have been published (Rois-Díaz et al., 2006) as well as several books and book chapters and papers on the role of AF in the adaptation and mitigation of climate change in agricultural systems (Mosquera-Losada et al., 2005, 2018b; Nair et al., 2009; Rigueiro-Rodríguez et al., 2009; Howlett et al., 2011a,b; Mosquera-Losada and Prabhu, 2019; Santos et al., 2022).

From a biodiversity point of view, the increase in productivity per unit of land is based on biodiversity, which allows improved efficiency in the use of the resources (radiation, water, nutrients, etc.) as found by McAdam et al. (2009). The presence of a tree in a treeless land causes disturbances and generates microclimates within the treeless/tree plots (Rigueiro-Rodríguez et al., 2012). In fact, the tree/shrub modifies the main ecological factors (radiation, temperature, and humidity), creating microhabitats for different species that differ from those growing up in open areas, therefore, increasing biodiversity per unit of land (McAdam et al., 2009; Santos et al., 2022). The presence of animals also enhances AF due to the impact of different animals on different plant species selected, trampling, and feces (Rigueiro-Rodríguez et al., 2012). In addition, AF practices have also been impacted at a landscape level, which is used to improve crop production (Mosquera-Losada and Prabhu, 2019). This is the case of many eastern countries, such as Bulgaria or Hungary, which planted many forest belts, hedges, and hedgerows in the past to reduce the impacts of climatic factors (e.g., wind), therefore, creating microhabitats for many invertebrate species (Takáczs and Frank, 2009; Kachova et al., 2018). Actually, the use of woody vegetation and AF has been highlighted in the first report of the European Commission in the EU biodiversity strategy 2030 (European Union (EU), 2021), where the important role of woody vegetation on pollination has been described (Santiago-Freijanes et al., 2018b).

2.2. Ecosystem services

Agroforestry (AF) biomass production is generally higher than that linked to monocrops, when both the crop and the woody perennial production are considered. Finding uses for both components (woody perennial and agricultural components in the understory) are essential to foster AF expansion in the EU. The advantages of AF production are based on the increased biodiversity (by comparison with polycultural and monocultural systems), which allows multipurpose use of land and optimize the use of the resources (radiation, temperature, water, and nutrients), if adequate components (tree/shrubs/crops/animals) are integrated and adequately managed by considering the positive interactions among them (Mosquera-Losada et al., 2016; Santos et al., 2022). Moreover, the woody perennials promote microhabitat connectivity at the landscape level to support biodiversity. The main productive advantages for the producers of the selected tree species and crop varieties are the improvements in the farm's economic balance as the understory is used to generate farmers' income and to avoid understory maintenance (Mosquera-Losada et al., 2016). Moreover, the optimization of the use of the resources generates an increase in biomass production and therefore causes a sustainable way of land intensification. The land equivalent ratio (LER) indicator reveals that 1 ha of AF is equivalent to 1.4 ha of crop+forestry biomass production when they are grown separately (Dupraz and Liagre, 2004).

From a climate change point of view, the promotion of woody vegetation is essential for both mitigation and adaptation (Mosquera-Losada et al., 2017). However, it has to be considered that climate change may have an important impact on already existing agroforestry systems such as those linked with the dehesa, trees, and shrubs dying due to climate change. AF has been demonstrated to be useful in reducing the risk of GHG emissions related to fire when the “understory fuel” is consumed by animals (Damianidis et al., 2021). Concerning mitigation, AF has an enormous capacity of increasing carbon (C) sequestration in agronomic and forestland, while avoiding or counteracting emissions and the effects of catastrophic events mostly due to the increase of resilience. In terms of adaptation, there is fragmented information where AF practices have demonstrated to be able to reduce temperature variation by (a) the shade the trees cause, (b) the reduction of wind speed that tree barriers cause to surrounding croplands, and (c) the reduction of the effects of catastrophic events such as flooding (due to the reduction of the impact of heavy rainfall on soil and the better soil structure that the root of the trees provide which enhances water infiltration and reduces runoff) on crop production (Palma et al., 2018; Mosquera-Losada and Prabhu, 2019). Moreover, several researchers have estimated the capacity of AF to mitigate climate change, by counteracting the emissions at the farm scale, due to carbon (C) sequestration in the subsoil (Howlett et al., 2011b). In addition, trees are able to maintain temperature during the hot waves, which reduces the exchange of greenhouse gases (GHGs) with the atmosphere (Rigueiro-Rodríguez et al., 2009). In order to tackle these mitigation and adaptation issues, AF modeling is considered essential, since the yields of trees cannot be directly determined within the duration of a short-term project. SAFE models are based on the development of a range of biophysical models to describe tree–crop interactions over longer time periods, like those described for Pinus radiata by Ferreiro-Domínguez et al. (2022a,b,c). The Yield-SAFE model is a parameter-spare model (Van der Werf et al., 2007) for agroforestry practices, mainly dealing with silvoarable or alley cropping. The outputs from the Yield-SAFE model were also used to inform bioeconomic models, such as Farm-SAFE, by comparing the financial and economic benefits of silvoarable agroforestry in relation to monoculture arable or forestry systems (Graves et al., 2011).

3. European agroforestry practices typology

Mosquera-Losada et al. (2018b) identified AF as a set of practices in which woody vegetation, either trees or shrubs, is grown in combination with agriculture on the same unit of land [Food and Agriculture Organisation (FAO), 2015]. This definition is highly relevant as it includes AF practices associated not only with trees but also with livestock production, more adapted to Southern Europe's drier areas. In fact, AF has two main components (woody and herbaceous vegetation) which could be enlarged to a third component, livestock, if silvopasture is practiced (Mosquera et al., 2009). Human is the fourth component or actor who artificially modifies the relationship between the former components, depending on the main agricultural or forest product pursued by the AF system and agroecological conditions (Mosquera et al., 2009). AF is based on a few practices at the plot level, which combined can provide many systems at the farm level (Nair, 1993; Nair et al., 2022). The most recognized ones are associated with the spatial use of the woody perennials and include the silvopasture, silvoarable/alley cropping, homegardens/kitchengardens, woody linear landscape strips, and forest farming (Table 1), as described by Mosquera-Losada et al. (2018b). Mosquera-Losada et al. (2016)described two main spatial AF practices: silvopasture and alley cropping/silvoarable, which can be enlarged to a third one, named woody linear landscape strips if protection against water contamination (riparian buffer strips) or wind (hedgerows, hedges, and windbreaks) are pursued (Table 1). The fourth practice is homegarden or kitckengarden known as the implementation of silvopasture (e.g., chickens) or silvoarable (vegetables) in urban and peri-urban areas, a practice nowadays promoted by some municipalities across Europe through the Covenant of Mayors launched in 2009 by the European Union and with more than 10,000 municipalities currently involved (European Union (EU), 2022). Finally, the obtention of agricultural products from the understory in forestlands is known as forest farming. From those, silvopasture is the most extended AF practice in Europe, occupying 17.78 million ha in Europe, which together with the silvoarable practices (360 thousand hectares) (Mosquera-Losada et al., 2016, 2018a) reaches almost 20 million hectares of AF practices in Europe. Out of these, there are agroforestry systems implemented in farms using different agroforestry practices (mainly silvoarable and silvopasture) in Europe, such as the 3 million ha of dehesas and montados in Europe (Moreno and Pulido, 2009) and the 40 million ha found in Baltic countries of Europe (Jernsletten and Klokov, 2002). Silvopasture was, together with the silvoarable practices, the most ancient AF practices in Europe, dating from the Neolithic period (Pinhasi et al., 2005), starting in the East, and later on moving on to the west part of Europe (Mosquera-Losada et al., 2012). Woody linear landscape strips are usually naturally developed, but they can also be deliberately planted to prevent water bodies' damage as recommended by the Association for Temperate Agroforestry (AFTA) (2015)in the United States.

Table 1. Spatial agroforestry practices in Europe [modified from the Association for Temperate Agroforestry (Nair, 1994; Association for Temperate Agroforestry (AFTA), 1997; Alavapati and Nair, 2001; Alavalapati et al., 2004; Mosquera et al., 2009; Mosquera-Losada et al., 2018a)].

There are agroforestry practices implemented at a temporal scale, usually on a year or multiple year bases, which use woody perennials, usually a shrub legume such as Ulexspp. was established for a period of 10 years, to restore soil fertility. Improved fallow with woody perennials is an ancient technique (legume Ulex used to improve soil fertility) to increase soil health that was used in many places across the globe. In Galicia, shrub legumes such as Ulex europaeus or Ulex gallii were sown by farmers to increase soil fertility through the inherent addition of organic matter and/or nitrogen. These shrub legumes were sown when the productivity of cereals (mainly wheat and rye) had been significantly reduced. The shrubs were allowed to grow up and annually harvested to provide animal bedding for stables, where the mixture with manure generated an excellent fertilizer and soil amendment. Ten years after sowing the shrubs were harvested, and the roots were extracted and fired in holes following an anaerobic burning in a process named “troleiras,” therefore, producing biochar that was afterward applied in the fields. The former shrublands were again sown with cereals, mainly wheat or rye, and became highly productive. Moreover, the period of 10 years with shrubs caused a clear depletion of weed bank seeds in the shrubland sown fields, appearing the cereals clean of weeds without the need for any mechanical treatment.

The most relevant AF practices to promote Smart Climate Change Agriculture in Europe are silvoarable and silvopasture (Mosquera-Losada et al., 2016), which can be implemented in different types of lands such as agriculture or forestry (Table 2). Most often, new AF sites are obtained by planting trees in arable land (silvoarable) to provide several benefits (profitability, environmental benefits, biodiversity, etc.). Similar benefits, however, may be achieved when AF is implemented in existing orchards that might otherwise be abandoned or removed for lack of profit, such as millions of hectares of olive orchards in Europe (Rodríguez-Rigueiro et al., 2021). For example, due to the high harvesting cost and the decoupling of agricultural funding from the production, traditional olive cultivation and other relevant fruit trees are rapidly becoming anti-economical in developed countries (Rodríguez-Rigueiro et al., 2021). Converting such landscape to an olive-based AF system, intercropping olives with other economically viable crops/animals can provide economic sustainability, allowing maintenance of a traditional agricultural landscape, which is also functional for tourism activities. Implementing multipurpose AF fruit trees such as walnut, chestnut, and cherry can be a win–win strategy for increasing valuable timber production in Europe as performed by companies such as Bosques Naturales across Spain. Silvopasture should be promoted as a way to control the understory (therefore, preventing the use of herbicides and reducing the use of fossil fuels when the control is done by mechanical means) not only in high-value tree plantations but also in forest lands by adding a key component to the agroecosystem: the megaherbivores. The megaherbivores in forest lands play a very relevant role in natural systems: increase biodiversity by reducing understory dominant species, by trampling, and by the selection of the different species and accelerate soil nutrient use by the understory and trees by increasing mineralization rate (urine, mainly composing by ammonia can reduce the C/N relationship), as described by Mosquera-Losada et al. (2012).