Impacts of climate change adaptation options on soil functions: A review of European case‐studies

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Abstract

Soils are vital for supporting food security and other ecosystem services. Climate change can affect soil functions both directly and indirectly. Direct effects include temperature, precipitation, and moisture regime changes. Indirect effects include those that are induced by adaptations such as irrigation, crop rotation changes, and tillage practices. Although extensive knowledge is available on the direct effects, an understanding of the indirect effects of agricultural adaptation options is less complete. A review of 20 agricultural adaptation case‐studies across Europe was conducted to assess implications to soil threats and soil functions and the link to the Sustainable Development Goals (SDGs). The major findings are as follows: (a) adaptation options reflect local conditions; (b) reduced soil erosion threats and increased soil organic carbon are expected, although compaction may increase in some areas; (c) most adaptation options are anticipated to improve the soil functions of food and biomass production, soil organic carbon storage, and storing, filtering, transforming, and recycling capacities, whereas possible implications for soil biodiversity are largely unknown; and (d) the linkage between soil functions and the SDGs implies improvements to SDG 2 (achieving food security and promoting sustainable agriculture) and SDG 13 (taking action on climate change), whereas the relationship to SDG 15 (using terrestrial ecosystems sustainably) is largely unknown. The conclusion is drawn that agricultural adaptation options, even when focused on increasing yields, have the potential to outweigh the negative direct effects of climate change on soil degradation in many European regions.

Keywords: agricultural adaptation, DPSIR, regional case‐studies, soil degradation, Sustainable Development Goals

1. INTRODUCTION

Soil systems are fundamental to sustainable development due to their multifunctional role in providing services including biomass production (food, feed, fibre, and fuel); habitats for living organisms and gene pools (biodiversity); cleaning of water and air; mitigation of greenhouse gas emissions; contributions to carbon (C) sequestration; buffering of precipitation extremes; and provisions to cultural, recreational, and human health assets (Coyle, Creamer, Schulte, O'Sullivan, & Jordan, 2016; Montanarella, 2015; Tóth et al., 2013). The effects of climate change are associated with increases in temperature (T) and extreme weather events such as heavy rainfall, droughts, frosts, storms, and rising sea levels in coastal areas. These effects may also increase the threats to soil such as soil erosion, soil compaction, reduced soil fertility, and lowered agricultural productivity, which ultimately deteriorate food security and environmental sustainability (Lal et al., 2011). These climate‐related risks raise major concerns regarding the future role of soils as a sustainable resource for food production.

Climate change can affect soil functions directly and indirectly. The direct effects include soil process changes in organic carbon transformations and nutrient cycling through altered moisture and T regimes in the soil or increased soil erosion rates due to an increased frequency of high‐intensity rainfall events. Blum (1993) was among the first to frame a systematic concept of linking soil processes via soil functions to services for the environment and society in Europe. Climate change and soil management can change the ability of soils to perform soil functions, which, for the sake of simplicity, the study calls changes in soil functions. Several studies have assessed the effects of climate change on soil functions (Coyle et al., 2016; Ostle, Levy, Evans, & Smith, 2009; Xiong et al., 2014). For instance, in organic‐rich soils in the UK, increased T and decreased soil moisture linked to warming or drought were observed to reduce the C storage capacity (Ostle et al., 2009).

The indirect effects of climate change on soil functions include those that are induced by climate change adaptation options. Agricultural management can mitigate climate change effects, for example, through increased soil organic carbon (SOC) sequestration (Haddaway et al., 2015). Farmers may implement adaptations as a result of multiple, intertwined driving forces, including market price changes, new technologies, and improved knowledge in combination with climate change (Reidsma et al., 2015b). Regarding European agriculture, several scenario studies have investigated agricultural adaptation options in response to climate change, including the introduction of irrigation regimes in drought‐prone areas, crop rotation changes, increased fertilization rates on cropland, amended soil tillage practices, and cultivation of melting permafrost soils (Mandryk, Reidsma, & van Ittersum, 2017; Schönhart, Schauppenlehner, Kuttner, Kirchner, & Schmid, 2016; Ventrella, Charfeddine, Moriondo, Rinaldi, & Bindi, 2012a).

Although ample knowledge is available for the direct effects (although the interactions are not completely understood), evidence of the indirect effects of agricultural adaptation options on soil functions is more scattered and difficult to derive experimentally because it depends on an uncertain future climate and corresponding adaptation. However, the anticipation of development pathway impacts is a precondition for decision‐making.

Although farm management concerns the local field level, the multiple soil functions need to be maintained and improved at higher spatial aggregates to achieve the Sustainable Development Goals (SDGs) formulated by the United Nations agenda 2030. Montanarella and Alva (2015) assessed soil functions as being particularly relevant for three of the 17 SDGs, namely, SDGs 2 (achieving food security and promoting sustainable agriculture), 13 (taking actions on climate change), and 15 (using terrestrial ecosystems sustainably, reversing land degradation, and halting biodiversity loss).

The objective of this paper was to review case‐studies on future adaptation options in European regions for their information on how adaptations may affect soil functions and what that means in the context of the SDGs. Taking current climate systems and management practices as counterfactuals, the cases were used to assess how future climate change in combination with adaptation options may impact European soils. The regional case‐studies resulted from the European Joint Programming Initiative on Agriculture, Climate Change, and Food Security (FACCE‐JPI) knowledge hub MACSUR (Modelling European Agriculture with Climate Change for Food Security; http://www.macsur.eu). MACSUR brought together researchers across Europe to improve the understanding of climate change impacts and adaptation potentials on European agriculture.

2. MATERIALS AND METHODS

2.1. Study area and climate

Climate change adaptation options and resulting soil impacts are likely to be diverse across Europe due to heterogeneous biophysical and socio‐economic production conditions. Additionally, research design likely determines conclusions on adaptation options and their impacts in a region. To tackle both bio‐physical and socio‐economic dimensions, 20 case‐studies across Europe were assessed at the NUTS 2/3 level (Figure 1 ). Each case‐study undertook an integrated assessment with quantitative tools (e.g., scenario modelling) or qualitative, stakeholder inclusive tools or a combination of both. Published results from case‐studies were compiled and further substantiated with information from 23 involved scientists—most of them co‐authors of this article—via a semi‐structured questionnaire (Appendix S1). This led to a unique data set that reflects the impacts of adaptation options on soils across Europe. The 20 case‐studies represent 13 European countries and cover 11 of the 13 major environmental zones of Europe (Metzger, Bunce, Jongman, Mücher, & Watkins, 2005). This classification represents the environmental heterogeneity of Europe and utilizes European ecological data sets for climate, geomorphology, geology and soil, habitats, and vegetation. The two zones not presented in the sample are Anatolia and Lusitania.

Location of the 20 case‐study areas and their environmental zones in Europe as classified by Metzger et al. (2005): 1—Mostviertel (AUT), 2—Broye (CH), 3—Brandenburg (DE), 4—Hovedstaden (DK), 5—Norsminde (DK), 6—Guadalquivir Valley (ES), 7—North Savo (FI), 8—Massif Central (FR), 9—Foggia (IT), 10—Oristanese (IT), 11—South Tyrol (IT), 12—Baakse Beek (NL), 13—Flevoland (NL), 14—Hobøl, Østfold (NO), 15—Jæren, Rogaland (NO), 16—Lowland Trøndelag (NO), 17—Romerike Akershus (NO), 18—Kujawsko‐Pomorskie (PL), 19—Transylvanian Plain (RO), and 20—NE Scotland (UK) [Colour figure can be viewed at http://wileyonlinelibrary.com]

To classify the case‐studies in terms of soil types, the World Reference Base for Soil Resources (FAO, 2006) was used. The 20 case‐study areas cover the 15 most common arable soil types of the 32 World Reference Base types (Table 1 ). Table 1 also lists the features of climate change scenarios that are relevant to agricultural production, land use and farming systems, methods employed to obtain the results, and key publications for each of the case‐studies. Regarding the assessment methods, most studies (17 out of 20) modelled the effects of alternative adaptation management options under climate change on yields and environmental impacts. Such adaptation options were identified by means of stakeholder interaction with regional farmers or extension services in 14 cases and by researchers in the other cases. Therefore, the adaptation options that were regarded as the most suitable by farmers could be identified. Three case‐studies simulated changing climatic conditions by employing field experiments at different locations for studying adaptation options (e.g., crop rotation and no tillage).

Table 1

Characteristics of the 20 case‐studies

Note. GIS = Geographic Information System; T = temperature; WRB = World Reference Base.

2.2. Analytical framework

The Driver–Pressure–State–Impact–Response framework was used to study the impacts of climate change adaptation options on the soil functions and SDGs (Figure 2 ). The framework conceptualizes complex sustainability challenges and provides insight into the relationships between the environment and human beings (Gabrielsen & Bosch, 2003). It links the emergence of climate change (Drivers of change) and its impacts on natural and human systems to decision makers (farmers) who adopt new management practices (Pressures), which can lead to soil threats (State 1) and altered soil functions (State 2). Subsequently, the SDG targets (Impact) can be affected. As a result, policy action (Response) may be required (not covered in the present study). Adaptation options, soil threats, and soil functions are understood as dynamic processes over time, such that the ‘States’ in the Driver–Pressure–State–Impact–Response framework represent dynamic biophysical indicators and human practices.

Analytical chain of the study applied to the Driver–Pressure–State–Impact–Response framework. SDG = Sustainable Development Goal Source: Adapted from Gabrielsen and Bosch (2003) [Colour figure can be viewed at http://wileyonlinelibrary.com]

Adaptation options can be triggered by climate change. However, in reality, this driver is intertwined with other factors such as market conditions, technological development, farmer perceptions, and policy interventions (Mitter, Schönhart, Larcher, & Schmid, 2018; Techen & Helming, 2017). All case‐studies assessed climate change adaptation but in different scenario contexts. For the sake of comparability, only those scenarios and adaptation options were included in the review that had been developed from a farming system perspective intended to maintain farm profitability and improve yield level and stability. Other adaptation options focusing primarily on environmental (e.g.,reduced nutrient leaching) and/or social (e.g., employment, health, and culture) objectives (Mandryk, Reidsma, Kanellopoulos, Groot, & van Ittersum, 2014) were not included. The current situation of management practices and climate conditions is the counterfactual to which scenarios of future climate and management situations were assessed. However, in reality, transition is already occurring, and the adoption of adaptation practices can already be observed at individual farms in some cases (e.g., in North Savo, FI).

2.3. Characteristics of soil threats and soil functions

The European Commission's (2002) report lists seven major threats that cause soil degradation in Europe: soil erosion, decline in SOC, compaction, decline in soil biodiversity, salinization, contamination, and sealing. Because the study focuses on agricultural soil management, only the first five soil threats were considered. Soil contamination and soil sealing were excluded because the first is by definition associated with industrial, mainly point‐source pollution, whereas the latter refers to taking land out of production (European Commission, 2002).

Soils provide numerous functions to society. The European Commission (2006) lists seven key functions: food and biomass production; storing, filtering, transforming, and recycling water and nutrients; habitat and gene pool; SOC pool; providing raw materials; serving as physical and cultural environment for mankind; and storing the geological and archaeological heritage. In this study, focus was laid on the first four functions (Table 2 ), which are most relevant to agricultural land use (Schulte et al., 2014). The concept of soil functions was introduced in the Thematic Strategy for Soil Protection (European Commission, 2006), although it has not resulted in a legal implementation of soil conservation measures. Soil functions connect the physical, chemical, and biological processes in the soil system with the provision of benefits to society (Glæsner, Helming, & de Vries, 2014). Agricultural management affects the performance of soil functions in close interaction with geophysical site conditions. The optimization of one of the functions is often to the disadvantage of others. The assessment presents aggregated impacts of one to several adaptation options on soil threats and functions (Table 3 ).

Table 2

Soil functions and the linkage to the SDGs as classified by Montanarella and Alva (2015)