**1. Introduction**

A multitude of environmental, economic, political, and social challenges demonstrate that current practices of natural resource managemen<sup>t</sup> are unsustainable. In this context, current research shows that sectoral interdependencies among resources are increasingly important [1–6] and they influence each other through complex feedback [7]. With Agenda 2030, the international community has confirmed its commitment to adopting measures supporting sustainable development. Reflecting on sectoral interdependencies, the 17 Sustainable Development Goals (SDGs) are interrelated, and associated actions and policies require integrated and holistic approaches. Already since the 1990s, integrative policy concepts such as Environmental Policy Integration (EPI) and, more recently, the nexus around the conflicting interdependencies among water, energy, and land (WEL Nexus) have entered public and political agendas. The UN Global Sustainability Panel in its 2012 report highlighted the importance of the water, energy, and food nexus [8], and reinforced this focus in the 2014 UN Global Sustainability Development Report by attributing a special section to 'the climate-land-energy-water-development nexus' [8]. In 2011, the World Economic Forum in its 'Global Risks Report' identified the water-energy-food (WEF) nexus as one of its three cross-cutting global risks [9], and the World Business Council for Sustainable Development (WBCSD) under its 'Vision 2050' has centered several activities around the water-energy-land-food nexus [10]. The 'World Energy Outlook 2012' explicitly addresses the nexus among water and energy [11], and the U.S. National

Intelligence Council (US NIC) in its report 'Global Trends 2030' identified the nexus among water, energy, and food as one of four global megatrends [12]. With a focus on developing countries, the European Commission in 2012 published a report entitled 'Confronting Scarcity: Managing Water, Energy and Land for Inclusive and Sustainable Growth' [13]. On a global scale, providing all people su fficient access to clean water, adequate nutrition and a clean, reliable source of energy has been the primary objective. Within Europe, however, su fficient access to these resources has long been achieved and the focus instead has shifted to their e ffective and sustainable management:

"The e ffective managemen<sup>t</sup> of water, energy and land can and should contribute to economic growth. We draw on water, energy and land for a broad range of productive activities, from the production of food and fiber to the generation of power that moves our society. Water, energy and land are key inputs to the economic system, and thus play a crucial role in creating wealth [13]."

Effective managemen<sup>t</sup> first and foremost builds on political processes and governance structures. This holds especially true for the EU with its large territory and population, and its complex multi-level governance system. However, to this date, only limited research addresses integrated natural resources governance on the EU level. With regard to EPI, there is considerable literature on EU governance, but the concept is almost exclusively applied to individual sectors and policy fields such as agriculture [14] or climate and energy policies [15]. Also, according to the literature, the concept lacks implementation, since EU e fforts on including environmental concerns have been limited primarily to a strategic, discursive level [14]. In turn, with regard to the WEF Nexus concept, existing literature reveals that in the EU, the concept is often used to address links between only two sectors, or to analyze impacts of one sector on another. Examples include the nexus between energy consumption and economic growth [16,17], the electricity-fuel nexus [18], or the climate-energy security nexus [19,20]. More closely in line with the nexus approach as it was internationally promoted, Karabulut et al. [21] and Ziv, Watson, Young, Howard, Larcom, and Tanentzap [3] apply the water-energy-food nexus approach to case studies in the Danube river basin and the UK, whereas Siciliano et al. [22] analyze the relations between European large-scale farmland investments and the nexus. However, such comprehensive applications of the WEF Nexus concept seldom include governance aspects, e.g., [23]. This brief overview of studies demonstrates that, so far, little research has been conducted on the degree of integration of natural resource governance in the EU. This research gap needs to be addressed in order to overcome the prevailing silo-thinking, especially on higher governance levels such as the EU.

The aim of this paper is thus to review, in how far the European Union and its policy strategies are currently designed to pursue the objective of an integrated perspective on natural resources governance. It further investigates the challenges and barriers to a more coherent policy design. Therefore, current EU policies of high relevance for the water, energy, and land sectors are identified. The analysis of these policies' degree of integration is based on the literature on EPI di fferentiating between vertical and horizontal policy integration and the WEL Nexus literature on integrated governance. The paper provides a review of the current state of policy integration, which is assessed against the background of the two conceptual frameworks, EPI and WEL Nexus. The remainder of this paper is structured as follows. In Section 2, we further introduce the conceptual frameworks. In Section 3, the results of the qualitative in-depth analysis of implemented policy integration in current, nexus-relevant EU policies are presented. Section 4 includes a discussion of research outcomes and o ffers respective policy implications. The paper then concludes with a section on research implications, limitations, as well as further research needs (Section 5).

### **2. Conceptual Framework and Methodology**

This paper o ffers a review of EU policies relevant to energy, water, and land with regard to their degree of integration. Already in form of the EU's predecessor, the European Coal and Steel Community, governing natural resources has been a crucial field of common action. However, how individual resources are regulated and managed di ffers widely. Despite its historical role in European integration, energy policy has long been a strictly national prerogative. Article 194 of the Treaty on the Functioning of the European Union affirms the 'Member State's right to determine the conditions for exploiting its energy resources, its choice between different energy sources and the general structure of its energy supply' [24]. However, with the Energy Union in 2015, the EU has moved towards a more communitized energy policy, especially with regard to supply security, the internal energy market, and decarbonization efforts. Similarly, the provision of water is a national task, but against the background of environmental pressures, the EU has enforced several regulatory frameworks on water quality and the treatment of wastewater as part of its environmental policy and strives for integrating water concerns into related policy fields. Issues of land managemen<sup>t</sup> are primarily regulated by either EU environmental policies or agricultural policies. The Common Agricultural Policy (CAP) is a core concern of the EU, managing regulations and support for farmers and rural areas since 1962. It is among the most contested and financially significant EU policy fields. In sum, EU managemen<sup>t</sup> of natural resources, specifically energy, water, and land is very complex, and providing more integrated policies constitutes a significant governance challenge.

As mentioned in the introduction, there are primarily two concepts of relevance for integrating natural resources policies in the EU: EPI and the WEL Nexus. As analytical frameworks they provide the foil against which to reflect EU policies in order to identify and explain variations in integration. In this section, these concepts and the review approach will be introduced.

The review primarily draws on policy documents that can directly contribute to or are of relevance for achieving policy integration among the energy, water, and land policy sectors in Europe. For this purpose, the major political frameworks from the energy, water, environmental, and agricultural policy fields, as well as overarching policy documents dealing with sectoral interdependencies and general sustainability issues, were considered and qualitatively analyzed. For the identification of the relevant documents, keywords were deductively derived based on the available scientific literature [25,26] and searched for on the homepage of the European Union [27]. A list of the identified policy documents (N = 41) is provided as Supplementary Materials Table S1.

The policy documents were supplemented by relevant secondary literature. To this aim, a general web search was conducted for all specific policy measures of relevance (e.g., the Water Framework Directive (WFD) & CAP). This search produced both non-governmental and scientific reviews of different policies. The identified documents thus included original policy documents as well as policy reviews, totaling over 100 documents of relevance. These documents were then reviewed with regard to the assumptions and requirements about policy integration provided by the concepts EPI and WEL Nexus.

Before introducing the concepts, the terminology of policy integration is specified. The term policy integration, both in policy documents as well as in much of the scientific literature, is often used interchangeably with policy coherence. To carefully frame our research approach, in the remainder of this paper, we will differentiate between the two concepts based on Nilsson et al.'s [28] definition, according to which policy coherence refers to policy outputs whereas policy integration refers to policy processes and the institutional setting. Analytically, policy coherence thus results from an integrated policy framing. In actual policy-making, however, they can hardly be considered separately.

### *2.1. EPI Concept*

Both the EPI and the WEL Nexus concepts originate in the sustainable development discourse. The concept of EPI emerged in the 1990s, following the 1987 Brundtland Report, as a means to harmonize economic, social, and environmental policies [29]. The primary objective of EPI is to integrate environmental concerns into non-environmental sectors. EPI has been politically backed internationally, but especially by the EU [29]. However, this principle has seen little implementation since, and thus, research has turned towards investigating how governance structures are formed [29].

With respect to governance structures, EPI is often divided into a horizontal dimension (defined as the 'extent to which a central authority has developed a comprehensive cross-sectoral strategy') and a vertical dimension (defined as the 'degree to which sectoral governance structures have been "greened"') [30]. The vertical perspective primarily addresses procedures and interactions that have been established to promote environmental objectives within policy domains, such as sector-specific environmental targets [31]. Research, however, has shown that such sectoral strategies most likely will not automatically converge in order to best meet the overall objectives set in a comprehensive strategy [30]. Instead, successful EPI will require an even balance between both dimensions as well as the political will to achieve them [31–33]. Thus, the EPI concept accounts for environmental objectives within sectoral policies and a cross-sectoral strategy.

EPI has a long history in European policy design. The first legal basis was implemented as part of the Single European Act in 1986, demanding the integration of environmental objectives into other sector policies. This objective was further reinforced by the Maastricht and Lisbon treaties [34]. Although these treaties lay out a legal basis for the formal consideration of environmental objectives, their relevance has remained far inferior to sectoral objectives. Merely providing environmental concerns a legal basis, hence, does not guarantee an e ffective implementation [32]. Nonetheless, increasing consideration of environmental objectives becomes apparent, e.g., when looking at the development of the EU's Environment Action Programs [34].

A significant stream of EPI research on energy, water, and land policies has focused on its implementation in the CAP, e.g., [14,35]. In the literature, the food and agricultural policy is described as 'an extreme case of the ensuing compartmentalized and "exceptionalist" policy-making, where sector-specific policy ideas and institutions provide privileged access for sectoral interest groups and generate policies that benefit their members' [35]. Correlate finding of the research is that, despite a noticeable increase in the environmental discourse or rhetoric, the comparatively low priority of environmental policy and the 'closed agricultural policy network' make it di fficult to 'move from political commitment to genuine EPI' [14]. Instead, environmental concerns seem to fulfill mainly a strategic role in legitimizing existing practices [36]. Concluding this research, Alons [14] thus recently stated: 'Environmental objectives have become a variable in the agricultural policy-making equation, but its coe fficient remains small.' The example of EPI in agricultural policy is of direct relevance to the WEL Nexus approach, since environmental concerns in the agricultural sector very often directly relate to water concerns. Generally, however, EPI is actively promoted by actors in the broader environmental sector, whereas its implementation in other relevant policy sectors so far has had only limited impact [29]. So, while there is considerable literature on EPI, the concept has not been translated into the integration of natural resources governance in the EU.

### *2.2. WEL Nexus Concept*

The WEL Nexus is a comparatively recent concept, which was formulated in the context of the Bonn 2011 Nexus Conference as a means to optimize the managemen<sup>t</sup> of the interdependent resources with the twin objectives of achieving a sustainable, fair resource allocation and economic growth [2,37]. As such, it was introduced into EU thinking on sustainable development with the 2012 report "Confronting Scarcity: Managing water, energy and land for inclusive and sustainable growth" [13]. Although 'the nexus' has been extensively discussed on many levels during the past years, a consistent definition, or even terminology of the concept, does not exist. Most publications refer to the 'water, energy, food' (or 'food, energy, water')-security nexus (WEF/FEW Nexus) [2,5,10,38–43]. Others instead refer to the nexus among 'water, energy and land' (WEL Nexus) [13,44,45], or a combination of the two [46,47]. Also, some publications specifically investigate certain relations or sectors, such as the nexus between seafood and hydropower [48]. Others again explicitly include a fourth sector—namely climate—to the nexus [11,45,49,50]. Depending on specific perspectives, several publications address merely bilateral relationships among any two of the nexus sectors—most notably, the water-energy relationship, e.g., [1,11,51–64]. In this paper, the WEL Nexus perspective was chosen, since it reflects a holistic approach, including all three sectors and a focus on natural resources instead of exclusively human needs (i.e., food), while subsuming overarching climate aspects under the three sectors, respectively (e.g., emissions originating from agricultural practices or power generation).

Despite these variations in nexus terminologies and perspectives, their common ground is the realization that the sectoral fragmentation among water, energy, and land resources constitutes a crucial challenge in achieving sustainable development: 'silo-thinking' in managing these sectors leads to unintended side-effects and conflicts [65]. The aim is therefore to identify potential trade-offs as well as synergies, enabling the design of optimized, cross-sectoral resource managemen<sup>t</sup> strategies [2,39]. In contrast to different approaches of integrated resource managemen<sup>t</sup> (such as, e.g., integrated water resources managemen<sup>t</sup> or the integrated landscape approach), the idea of the nexus approach is to not prioritize an individual resource, but regard the water, energy, and land dimensions of the nexus at once, in their complex interrelations [39].

'The nexus' has been addressed by a number of different methods and disciplines in the past years. While current research suggests that quantifying theWEL Nexus could offer possibilities for an enhanced understanding of interconnections, related approaches and applications face several methodological obstacles [66,67]. Even though research on socio-economic issues increases the nexus, academic literature, so far, has been dominated by techno-economic approaches [68–71]. However, especially in industrialized countries, problems or inefficiencies in the use of natural resources are often caused by fragmented managemen<sup>t</sup> and governance of these resources. Common barriers are a high level of bureaucracy, historically grown sector policies and institutions, and differentiated responsibilities [33]. Thus, in this paper, the WEL Nexus approach is specifically applied to governance issues.

In this paper, we define the WEL Nexus as an analytical approach for optimized solutions of natural resources managemen<sup>t</sup> based on a holistic assessment of challenges and opportunities [13,39,72]. Applying the EPI terminology, we understand the nexus as a concept aiming at both vertical and horizontal policy integration across related policy fields, such as energy, water, or agricultural policy. Given these objectives, a nexus-enabled integrated policy-design for managing those resources should systematically account for the cross-sectoral effects of sectoral policies. Such an approach may 'support a transition to sustainability, by reducing trade-offs and generating additional benefits that outweigh the transaction costs associated with stronger integration across sectors' [2]. However, it will also likely alter the costs and benefits of existing policies and actions [13]. So although a nexus-enabled policy approach is expected to lead to better solutions, it may confront initial resistance in the different sectoral domains. Research has further shown that currently societies are only vaguely organized as to effectively implement and enact integrated (i.e., coherent) planning and action [1,38], and that even within the sectors, different policy packages often conflict with each other [73]. This holds true especially in the case of the EU, where sectoral fragmentation is strongly prominent [15]. Thus, the WEL Nexus offers a new, alternative approach for EU policy integration to advance.

With respect to managing the WEL Nexus, the EU is confronted with diverse conflicts of interests and unintended interrelations. Two prominent examples are the nitrogen pollution of ground water by agriculture [74] and the link between energy and water infrastructures in industry [75]. The EU emphasizes that internal policies affecting sustainable consumption and production patterns in the EU are important to help prevent resource scarcities [13]. Although a significant stream of research on the WEL Nexus has developed, its vast application and inconsistent definitions impose challenges on operationalizing the nexus for EU policies [76]. Attempts to achieve better coherence in the governance of the nexus resources inevitably lead to questions about the most adequate level of integration among the resource sectors. By emphasizing the need for considering interlinkages among the sectors, the nexus concept frames a new objective of policy integration among the related resource sectors. The nexus concept, in contrast to the main purpose of EPI, does not aim at implementing general environmental objectives into other policy sectors, but instead sets focus on the interlinkages between the water, energy, and land sectors [2]. Given this difference, existing, but often single-sector findings from the EPI literature can provide valuable insight, but will not be sufficient. Accordingly, a multi-sector analysis of the specific cross-sectoral interdependencies among the nexus sector policies shall provide the fundament for assessing the current state of policy integration in the European Union.

Reviewing EU policy integration based on the WEL Nexus concept faces methodological challenges. While the EPI concept provides specific analytical categories, the WEL Nexus concept has been heavily criticized for its lack of operationalization [76]. The EPI concept also entails di ffering interpretations and implementation options, but to a comparatively smaller degree [29]. As the above discussion shows, there is considerable overlap in the challenges for policy integration between EPI and the WEL Nexus concepts, given that water, energy, and land as natural resources are inevitably also part of the environmental sector. Though nexus aspects might fall under the concept of EPI, the WEL Nexus concept o ffers a more systemic perspective than the EPI concept. While the WEL Nexus approach looks at the overall integration of di fferent policy sectors, the EPI approach entails the integration of specific sectoral policy goals. Thus, both concepts complement each other well for reviewing the state of integration in EU policy. Based on the WEL Nexus' systemic perspective and EPI's analytical categories, in the subsequent review we will investigate EU policy integration with regard to cross-sectoral and nexus-informed strategies and policies, and the mutual consideration of related objectives within sectoral policies.
