The Politics of Environmental Consensus: The Case of the World Commission on Dams

Abstract Recent discussion of global environmental assessment processes suggests that the process of consensus creation is central to understanding the way knowledge is produced and conclusions are reached. Here we contribute to this literature by providing a case study of the World Commission on Dams, which brought together supporters and opponents of large dams, at the height of controversy about dams in the 1990s. The Commission reviewed evidence and formulated guidelines for best practice, finding a way through a political stalemate. The article draws on interviews with those involved in the Commission and discusses the historical context, form of stakeholder representation, time horizon, and leadership style as consensus-enabling conditions. We conclude that an ambitious consensual process was successful within the life of the Commission, but at the cost of carrying external actors with it, leading to challenges with dissemination and uptake of consensual recommendations.

This was an enormously stressful experience, because the Commission was ultimately always one step away from collapse. The confrontation had not been suspended, there was no cease-fire agreement, different dam projects in the entire world were rumbling, and it was as if we had to walk through a minefield all the time; but this experience of coming to an agreement fascinates me until today: no one believed it to be possible, that the Commission could write a report that everyone signs off.
-a WCD commissioner Ecosystem Services (IPBES) seek to synthesize scientific knowledge for policy makers but are also arenas of contestation within which "competing knowledge-claims and diverging values and interests are articulated" (Borie et al. 2021, 2). GEAs differ in their knowledge practices, the ways in which knowledge is made, ordered, and authorized. The IPCC, for example, is perceived as "top-down" and science driven (Pearce et al. 2015), while the IPBES has sought to engage with a range of actors and knowledges (Borie et al. 2021). The nature of the process of consensus making, the precursors and conditions of debate and negotiation, the range of actors involved, and their strategies for coming to an agreement in different contexts are increasingly recognized as important in understanding the workings of GEAs (De Pryck 2021).
In the case of the IPCC, the scientific consensus that lies behind the product gives great epistemic authority to its reports, although it also means that potentially only the "lowest common denominator" of fully agreed facts may be included, excluding relevant knowledge that does not meet the narrow standards of full consensus required for inclusion (Borie et al. 2021, 12). However, even such attempts to produce an abstract, scientific "view from nowhere" are in practice characterized by complex political struggles about knowledge among political actors. Thus, De Pryck (2021) argues that while the IPCC's "Summary for Policy Makers" of the 2014 Synthesis Report is a "consensus in the singular," which favors only the strongest, unanimous scientific conclusions (but may hide uncertainties), it is also "consensus in the plural," juxtaposing diverging views. Both types of consensus are the result of compromises, negotiations, and scientific diplomacy.
In contrast, the IPBES has sought not only to take account of diverse and sometimes contrasting ideas and perspectives through its conceptual framework (e.g., those of Indigenous people as well as scientists) but also to incorporate them into the final product (Borie et al. 2021). The IPBES places emphasis on taking decisions consensually, fully accepting that reports and documents may contain different and contrasting perspectives (Borie and Hulme 2015). Consensus can be seen as a feature of governance that serves to stabilize decisions and achieve closure in negotiations and complex political processes that are otherwise characterized by conflicts over questions ranging from epistemology (what counts as knowledge and whose knowledge counts) through representation and process (Montana 2017).
In this article, we seek to contribute to the literature analyzing the process of consensus creation in international bodies in the context of contested and contentious environmental issues. We focus not on contemporary GEAs (the IPBES or IPCC) but on the work of the World Commission on Dams ( WCD), which between 1998 and 2000 sought to secure a consensus over the contentious question of how large dams should be designed and built. Through our analysis of new qualitative interviews with those at the center of the WCD, we identify a series of considerations that favor consensus creation and may comprise enabling conditions for consensus within GEAs more generally.

The World Commission on Dams
The WCD was active between 1998 and 2000 (Dubash et al. 2001; World Commission on Dams [WCD] 2000). It was an unusual institution, different in many ways from the IPCC and IPBES. The Commission emerged in response to global struggles between supporters and opponents of large dams in the 1980s and 1990s. Supporters cited benefits like electricity, irrigation, and flood control. Opponents highlighted the social and environmental problems of involuntary displacement, loss of livelihoods and cultural practices, and impacts on river ecology (Schulz and Adams 2022).
The WCD was conceived in 1997 at a stakeholder workshop hosted by the World Bank and IUCN (then called the World Conservation Union) in Gland, Switzerland, and subsequently launched with the support of both organizations. The WCD was composed of twelve commissioners with previous expertise in the fields of dams and development, who were assisted by a technical Secretariat and whose work was overseen by a large Stakeholder Forum. The mandate was to review the development effectiveness of large dams and to propose rules and guidelines that could guide better decision-making and dam planning in the future. It published a widely publicized final report alongside numerous technical reports (WCD 2000).
There is a substantial body of literature on the WCD. It includes the report of the Commission itself (WCD 2000), an external review of the Commission's work by the World Resources Institute (Dubash et al. 2001), and retrospectives by people involved in the process (e.g., Briscoe 2010; Moore et al. 2010;Scudder 2005;Steiner 2010). A full review of literature on the WCD is beyond the scope of this article (see Schulz and Adams 2019 for an overview). Several papers comment on the process of consensus making within the WCD, although none make it their primary focus. Dubash et al. (2001) note that the Commission lacked aggressively pro-dam voices, suggesting that this made it easier to reach consensus between dam critics and supporters. Conca (2002) hints that the WCD consensus was reached in a rare "window of opportunity" through skillful leadership and interpersonal dynamics. Brinkerhoff (2002) highlights both the nonhierarchical relationship between commissioners and the severity of the conflict between dam supporters and opponents as enabling conditions for the WCD's "partnership approach." Dubash draws attention to several aspects of the WCD's collaborative process: Dubash et al. (2001) suggest that the WCD consensus was the result of shared learning among the commissioners, and with Dingwerth (2007) they question the extent to which the consensus reached by the WCD was in fact shared by outside actors. Dubash (2009) notes that the WCD followed a deliberative approach in which commissioners did not insist on predefined fixed positions, allowing a logic of persuasion to prevail over bargaining. Dingwerth (2007) suggests that a climate of mutual trust emerged over time and that initial bargaining or strategic interactions were replaced with de-emotionalized and rational interactions.

Investigating Consensus Making in the WCD
Our account of consensus making in the WCD is informed by interviews with those who were central to the Commission's work. We focus not on what arguments are traded off against others but on how a group of people actually engaged together to reach a consensus. We seek to respond to the challenge to study the "production of 'scientific/diplomatic documents' as a whole, that is, as all-encompassing reports that need to reflect a commonly agreed position between experts and governments" (De Pryck 2021, 111, emphasis original), considering the practices and processes through which consensus is made.
Understanding the process of consensus making within a negotiating group like the WCD is a considerable research challenge (as noted by Dingwerth 2007), since only insider participants have the necessary insights, yet they may feel prevented from speaking about the process out of loyalty to the outcome and their colleagues (for an exception, see Owens 2015). We asked key actors to review their work some twenty years after the Commission's deliberations. Such a recall-based approach avoids some of the immediate difficulties of confidentiality with contemporaneous interviews but is, of course, clearly subject to various forms of memory bias. We have sought to minimize these by in-depth reading of the WCD's numerous reports. The time gap might have allowed former commissioners greater flexibility to speak frankly about their work, considering the time that has passed and the framing of the research as a historical account of the WCD's legacy. It may also have sharpened respondents' views on what aspects truly mattered, though it is important to acknowledge psychological biases toward positive long-term memories ( Walker et al. 2003), potentially making respondents focus on achievements and positive experiences, rather than challenges and conflicts.
We interviewed ninety-one people, including eight WCD commissioners; 1 ten WCD Secretariat staff; eight research fellows based in the WCD Secretariat; ten participants of a 1997 workshop in Gland, Switzerland, where the mandate for the WCD was agreed upon; twenty-five members of a WCD Stakeholder Forum; and thirty-nine consultants, advisers, and lead writers of contributing reports. All surviving commissioners, Secretariat staff, lead writers of reports, and consultants listed in the WCD report were approached for an interview, where contact details could be identified. Stakeholder Forum members were approached where their names appeared in participant lists from separate Forum meeting reports, since the main WCD report lists only participating organizations, not names of individuals. Casting the net widely was useful since WCD participants' formal status may not necessarily have matched their actual commitment, with some formally powerful figures comparatively detached and other formally unimportant participants contributing a great deal of empirical insights in interviews. Some respondents had multiple roles, for example, as participants at the pre-WCD Gland workshop and then within the Commission or as consultants and Stakeholder Forum members. Interviews were conducted in person (13), via telephone (20), on Skype (48), and via Zoom (1) in 2019 and 2020. Nine (comparatively less substantial) responses were provided in writing only. Interview transcripts and written responses were coded with NVivo 12. Prior to conducting interviews, interviewees were informed that their names would not be attributed to any quotes cited in publications, instead using their organizational roles only. The content of interviews differed depending on the respondents' specific role in the WCD process but broadly covered respondents' personal backgrounds and involvement in WCD, the compilation of the WCD knowledge base, their perspectives on WCD consultation events, interactions between stakeholder groups, consensus-making strategies, and the legacy and impacts of the WCD.
The twelve commissioners of the WCD represented a diversity of perspectives in terms of geography, disciplinary training, sector, and experience with large dams. There were four women and eight men. Five commissioners, including chair and vice-chair, were from the Global South, and all continents were represented by at least one commissioner. The Commission's chair was Kader Asmal, a longtime antiapartheid activist and human rights lawyer, serving as minister for water affairs and forestry in the first post-apartheid government of South Africa under Nelson Mandela. Its vice-chair was Lakshmi Chand Jain, an Indian social activist and former high commissioner of India to South Africa. Achim Steiner, secretary-general of the Commission (formerly an adviser with IUCN), obtained the status of full commissioner during the Commission's work. Further commissioners were social and environmental activists, academics, engineers, and government officials from the United States, India, Australia, Brazil, the Philippines, and Sweden.
Our analysis focuses on four themes that were discussed in the interviews: historical context, the politics of representation, leadership and political skill, and the politics of time. As noted, these themes have been discussed in previous literature on the WCD (e.g., Brinkerhoff 2002;Conca 2006;Dingwerth 2007;Dubash 2009), but no previous study has focused primarily on their importance in enabling consensus. These themes, which were widely shared by interviewees, emerged through repeat reading of interview transcripts and coding of statements in NVivo 12. Although our study primarily sought to respond to recent theoretical debates on the role of consensus in GEA, the comparatively strong importance of empirical material in our research reflects recent work on institutional epistemologies (Borie et al. 2021), which is primarily case study driven and which is also underrepresented in previous publications on the WCD (with the exception of Dubash et al. 2001). Owing to space constraints, we first provide a primarily empirical account of the four factors in the following section, before linking our findings with global environmental politics literature in the final section of this article.

Historical Context and the WCD Consensus
In the case of the WCD, the historical context was a dominant factor in the way political processes played out in practice. As alluded to in the opening quote, large dam building in the 1990s had become an extremely conflictive and globally visible issue, in which transnational networks of anti-dam activists on one side and the World Bank and other dam builders on the other invested significant time and resources in defending their points (Schulz and Adams 2022). Although the World Bank was only directly involved in a small percentage of large dam projects globally, it was an obvious campaigning target owing to its size, global reach, and perceived role as a standard setter for dam development. Anti-dam opposition had slowed dam building considerably, making it more costly to the point that both sides felt constructive engagement could be to their benefit (see also Conca 2006). Paradoxically, this history of strong conflict may have enabled, not obstructed, consensus making, a proposition also made by Brinkerhoff (2002) and a more general phenomenon noted by Ansell and Gash (2008).
The historical context may also have mattered in a very different way. The Commission was based in post-apartheid South Africa, a few years after its transition to democracy. Interviewees spoke of this as an inspiration for the WCD's work: overcoming the differences between supporters and opponents of large dams seemed to be a minor challenge compared with the achievement of ending apartheid between South Africa's different ethnic groups. The WCD's location in Cape Town was thus not only of symbolic importance for the recognition of perspectives from the Global South; it also came at an opportune time. This exceptionally inspiring context may have played a part in creating the sense of momentum needed to fulfill the WCD's mandate and, as some interviewees pointed out, also sharply contrasted with the locations and associated contexts of most other settings for GEAs and politics.

The Politics of Representation in the WCD
The key institutional design factor identified by our interviewees in the case of the WCD was the politics of representation and nonrepresentation in the Commission, although the effects were slightly paradoxical. On one hand, its members were selected due to their strong profiles and firsthand experience with dams and development. In this sense, they acted as representatives of certain stakeholder groups, interests, preferences, and geographical contexts. On the other hand, the WCD consistently emphasized its independence, meaning that commissioners were not tied to their constituent stakeholder groups. Although a degree of individual consultation between individual commissioners and their stakeholder networks did occur throughout the process, commissioners were not meant to seek consent from the groups that they "represented" when drafting their report and its recommendations (cf. Dubash et al. 2001, 90). One of them explained, "Yes, we were chosen from different stakeholder groups …, but the process was not that each commissioner member was representing a group. … Jan Veltrop … wasn't required to check with all of ICOLD [International Commission on Large Dams] and have ICOLD tell him that, yes, he could sign the report." This balancing act between representation and nonrepresentation was therefore part of the WCD's consensus-making recipe. Indeed, we suggest that this "weak representation" contributed to the consensus achieved by the WCD. As Dubash (2009) notes, the WCD's practitioner-commissioners differed from those in other commissions, such as Brandt and Brundtland, whose members had been mostly eminent personalities, detached from the everyday reality of the subjects they investigated. However, the WCD shared the insistence of previous commissions on internal autonomy and independence from outside influence. Too strong an emphasis on representation might have caused deadlock, because both anti-dam and pro-dam views were so entrenched among the commissioners' constituencies. Commissioners had to undergo a shift from representing their stakeholder groups to representing the WCD; that is, they were taking on a novel, additional professional identity.
This representational shift was easier for some commissioners than for others. Many interviewees noted that Medha Patkar, who had devoted her life to defending the rights of impoverished dam-affected people (often at the cost of her own health and safety, when going on hunger strikes or being jailed), faced particular risks in being seen to compromise her position. Even if she shifted her positions in private, any public statement not strongly critical of large dams would have seemed a betrayal of her movement and the people for whom it fought. Conversely, pro-dam industry representatives within WCD did not face such restrictions. Göran Lindahl, though CEO of ABB, a large company manufacturing turbines for hydropower dams, did not negatively impact ABB's business by agreeing to the WCD consensus, considering that ABB had begun to withdraw from the large dams business during the course of the WCD. Jan Veltrop, former president of ICOLD, was already retired and was thus free to shift toward a more critical position on dams, making use of his right to "not represent," which some have interpreted as the result of learning about new evidence, rather than compromising on a pro-industry position (Dubash et al. 2001). Even though Veltrop's support for the WCD consensus, which included a recognition of the often severe environmental and social impacts of large dams, enraged other ICOLD representatives (van Robbroeck 2015), his career in the dams sector did not stop him from signing.
Representation was not a concern only for commissioners. The WCD architecture also included a Stakeholder Forum with sixty plus members, meant to represent all stakeholder groups with an interest in large dams, from the most critical anti-dam movements to the most supportive pro-dam industry representatives. Governments from North and South, development banks, researchers, and many moderate voices were also present in the Forum. The WCD held three official Stakeholder Forum meetings (Prague, 1999;Cape Town, 2000;Cape Town/Spier, 2001), 2 and stakeholders were encouraged to send submissions and comments to the WCD Secretariat throughout.
Civil society organizations were particularly active in sending written submissions and commenting on WCD reports. This may reflect the strong personal networks of the civil society commissioners, as well as the fact that the WCD was seen as a key campaigning battleground among activists. The same cannot be said for governments and industry; as one government representative interviewed for this study explained, he had to represent the contradictory views of the different ministries of his federal government, as well as of the subnational state governments of his country, and not least of the diversity of views within the general population, all while continuing his everyday work as a government official. This impossible task of representation contrasted with activist Forum members, some of whom described the WCD as a three-year full-time job in which they were free to defend a specific critical perspective on large dams.
The Forum was not able to directly influence the text of the WCD's final report, its "consensus product." It did not receive a draft of the WCD's final report to comment on, meaning that its members did not have the chance to ensure it represented their views. Both critics and supporters of the WCD saw this as a key failure of the WCD process (see also Dubash et al. 2001). Several industry associations rejected the WCD report, despite their participation in the WCD Forum and their general support for many of the WCD's guidelines (Schultz 2002). As a commissioner explained, time was running out, and having a consultation on the final report with the wider Forum would have meant that the process could not have been completed: "We made a judgment call. … It's hard enough for the twelve of us to come to agreement, and if we just open up a draft before it's really final, it's going to become a political football before we have even come to an agreement on the text. And then once it becomes that political football then the pressure will be on each of the twelve commissioners again to be locked into our stakeholder group." Forum members also lacked the shared experiences that the commissioners had had over the course of the WCD process, and which perhaps helped them to reach their consensus. Some Forum members attended only one or two meetings. Even some of those who were supportive of the WCD commented that their input into the process had not been very substantial. Thus, it is questionable whether a consensus could have been found among Forum members on the final WCD report and its recommendations, even if sufficient time had been allocated for Forum members to comment. Reaching a consensus therefore required setting boundaries for representation and participation. While this helped the process to conclusion, it negatively impacted the sense of ownership and subsequent dissemination among some stakeholder groups. Once more, "weak representation" facilitated the WCD consensus, but it also weakened its impact among the stakeholder groups represented in it.
The Time Horizon of the WCD Consensus creation, demanding collaborative elements such as developing a shared understanding and trust building, is both driven by and demanding of time (Ansell and Gash 2008), including in the deliberations of commissioners. Yet, our interviewees also repeatedly cited urgency and a shortage of time (the fact that the WCD's mandate was limited to two years) as a contributing factor in its success in reaching a consensus (which contrasts with Dingwerth's [2007] proposition that the limited available time negatively impacted consensusbuilding processes in the WCD). One staff member commented, "Certainly there was no shortage of strong opinions on all sides-and of, even, temper tantrums outside the Commission, within the Commission, within the Secretariatbut there was also a sense that 'no one else is doing this. If we don't, no one else will. We've got a deadline to deliver on. We've got to show something, so let's do this as credit to ourselves.'" The deadline served as a sharpening device to focus attention on a common objective, both among commissioners and among staff working for the WCD. While they may not have been united in their views on dams, the deadline served as an alternative unifying, consensus-making device. There was no time to dwell on disagreements.
When the WCD presented its final report in London in November 2000, its chair, quite proudly, described the event as a "wedding" and a "wake," since it marked the union between dam supporters and opponents but also the dissolution of the WCD (Asmal 2000). Indeed, the report itself ends with the oftquoted words "We have told our story. What happens next is up to you" (WCD 2000, 320), leaving no doubt about the Commission's intentions to end its activities for good. This is somewhat unusual, considering, for example, the case of global multistakeholder standard-setting organizations, which, once founded, tend to continue their activities indefinitely (see, e.g., Boström and Tamm Hallström 2013). A few interviewees criticized the Commission's abrupt end, one suggesting that the WCD was a "photograph," when what was needed was a "film." But others sought to emulate the approach. One staff member commented, "I really always respected the fact that one should set up an organization that serves a particular task, get it done to the best of your ability and then end." Years later, they tried to convince another organization to close up, saying, "You've achieved what you were set up to achieve and you've done it well. Now let's say job done, move on and go to different jobs.… That's brave, that's not weakness." The unifying force of a strong deadline not only helped overcome differences in perspectives on large dams; it also enabled the selection of this precise group of commissioners, as well as their staff. The commissioners were globally leading personalities within their respective sectors, with busy calendars. While it was possible to convince them to dedicate significant amounts of time for the limited period of the WCD's existence, the same would not have been possible in a more extended process.
Nevertheless, the WCD process was also sufficiently extended to allow commissioners to get to know each other on a personal level, forging trust through joint experiences while on fieldwork in remote locations or simply having coffee and dinner in breaks from work. Despite their different views, they were able to develop respect for each other (trust building is generally recognized as a key precondition for collaboration; Ansell and Gash 2008). Interpersonal relations were often mentioned as a very positive element of the WCD experience, with the time allocated to building them cited as key to explaining the WCD consensus (cf. Dubash et al. 2001, 89). One commissioner described the importance of time spent in the field as follows: "To have that sort of free time to get to know the other commissioners, talk through the issues that you might have different views on. Visiting those dam sites gave the space for that, rather than just in the meetings. It, sort of, allowed the commissioners to exchange ideas on a more … informal … basis. I think that was very effective in bringing the commissioners together." The composition of the WCD Secretariat was also very directly influenced by the limited time horizon. The two-year mandate attracted relatively young and ambitious characters from many different countries, who were willing to work extremely hard for a limited period of time, away from home. This sense of momentum would have been lost in a longer process. With most staff coming from outside South Africa, their work colleagues became central as a local social support system, creating a strong team spirit, which might not have been the case in a different temporal and geographical context. One Secretariat member commented, "Being in the Secretariat, you had a small place where people knew that in a year or two years, everybody would be back to wherever their life is … California or London or Berlin or Kenya or whatever it is. … So, I think that that was also very important to create a consensus." The same respondent suggested this contrasted sharply with conventional organizations, where power dynamics and institutional inertia often mean that those who have been with an organization for a long time will not listen to newcomers, hampering innovation and open and constructive dialogue.
Many respondents drew parallels with the WCD's successor, the United Nations Environment Programme (UNEP) Dams and Development Project (UNEP DDP), which was put in place to disseminate the WCD's messages and to continue a global multistakeholder dialogue, with special emphasis on reaching national governments. The UNEP DDP process extended from 2000 to 2007 and, according to some interviewees who participated in it, became caught up in the slowness induced by UN bureaucratic procedures and diplomatic conventions. This eliminated the sense of possibility and momentum that had been present in the WCD.

Political Skill and Facilitative Leadership for Consensus
The most common explanation for the WCD's success in creating a consensus by participants was the political skill and leadership qualities of the WCD's chair, Kader Asmal, and its secretary-general, Achim Steiner. Numerous interviewees praised Asmal as a skilled political leader, explained by his past in South Africa's antiapartheid movement (cf. Dubash et al. 2001). Asmal had been involved in the complex negotiations between the African National Congress (ANC) and the National Party to develop a new South African constitution in the 1990s. Steiner was described as a young leader whose experience with WCD prepared him for bigger future tasks, as head of the IUCN (2001IUCN ( -2006, the UNEP (2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016), and the United Nations Development Programme (2017 to the present). His performance at the WCD left a lasting impression on many people, as per one observer: "Achim is a genius. I mean he's just the best manager I've ever seen in my life; to get people to agree on such a contentious debate, or beg to disagree at least, was amazing." What can be learned from their leadership style? Beyond attributing a negotiation success to two individuals and their personal backgrounds (as many interviewees chose to do), it is possible to identify specific qualities and techniques that have been linked with the journey toward a consensus. While some techniques were part of an explicit repertoire, described and employed as a tool in negotiations, many aspects of leadership style and political skill were much more implicit in the WCD.
Numerous interviewees noted that the most prominent (explicit) decisionmaking tool that Asmal used at commissioner meetings was one that he had employed in his previous work with the ANC, the "principle of sufficient consensus" (see also Dingwerth 2007, 88;Dubash et al. 2001, 87). This approach was an iterative process in which the group of commissioners first identified all areas of common ground on a topic before successively moving toward areas of disagreement. Areas with disagreement were often parked until a later point of time so that the work program could move ahead and any individual issue would not stop progress in general. Then, later, negotiations around the more contentious issues would take place, sometimes leading to a shift in position among commissioners or to a recognition or inclusion of multiple and diverging viewpoints on a specific topic.
The most visible example of this approach is a two-page dissenting note by Commissioner Medha Patkar included in the WCD final report ( WCD 2000, 321-322). This was the result of intense negotiations between Asmal and Patkar. In it, she sets out several areas of disagreement between her and the commissioners as a group. Doing this allowed her to sign off on a report that, in her words, "[did] not go far enough" (WCD 2000, 321). In her vision for development, there was no space for large-scale top-down development, but large dams, in turn, were inextricably linked with such a form of development (cf. Dingwerth 2007). Asmal understood that reaching a consensus that included Patkar demanded an opportunity for her to express the internal contradictions that she faced as a well-known anti-dam activist engaged in a process that set out to make policy recommendations for building (better) dams. Perhaps more noteworthy than the addition of two pages of diverging comments is Patkar's signature under the 300 plus pages of report that precede them, suggesting that Asmal's consensus-building techniques had been extremely successful.
Beyond their structured approach to decision-making, interviewees described both Asmal and Steiner as very good listeners who led not by imposing their views on others but by constantly updating joint positions for the greater good of a consensus. It may have helped that neither of them had built their previous careers on dams; this meant that they did not have previous committed positions on dams, or strong preconceived ideas about dam decisionmaking, and that listening was both a means of learning and a strategy for engaging with the commissioners. One WCD staff member explained, "Kader Asmal … did not feel the need to be the smartest man in the room, to throw his weight around. It's a tribute to Achim Steiner, as well. They saw themselves as catalysts, as facilitators. I think the phrase that Asmal used often was 'Being quick to listen, slow to speak.'" That said, the work of the WCD carries their signatures in several ways. The WCD final report includes a conceptual approach called the "rights and risks framework," which captures Asmal's experience as a human rights lawyer (although multiple other respondents claimed it as their own contribution to the WCD process). The report also consistently favors the language of choices, rather than trade-offs, in dam decision-making, a key concern of Steiner, as reported by one commissioner. The commissioner further explained, "Every dam is a choice and 1,000 choices are made in deciding to build that dam," going on to stress that these choices should not be made by national governments alone but in partnership with project-affected people. This approach highlights the agency of development actors and is very different from a modernist vision of large-scale development as the inevitable accompaniment of human progress, in which the grievances of small groups of dam-affected people have no space.
Some aspects of Asmal and Steiner's leadership in the WCD differed. Asmal was often described as an edgy character who would sometimes employ theatrical gestures to force progress in a negotiation (e.g., once, when fed up with a lack of progress, he left the meeting room to go home, only to return the next day); he also did not shy away from reprimanding staff and consultants who had a lower standing in the hierarchy and that he perceived to be interrupting the process. This meant that many people preferred approaching his adviser, Allan Taylor, who often acted as a go-between. Conversely, Steiner excelled at finding time for everyone's concerns, from the highest-ranking officials to junior interns and visitors to the Commission. Respondents commonly described him as a modest character, extremely skilled at people management and synthesizing information, and very ably catering to the big egos of those pertaining to the global strata of development. His multicultural background as the son of German immigrants in Brazil who had gone to school and university in the United Kingdom was also highlighted as a contributing factor to his successful leadership in the WCD. One of his (few) critics described him as a person who is overly willing to reach a compromise between diverging interests to avoid conflict (which could also be interpreted as a grudging compliment).

Understanding the Consensus on Large Dams
Existing research on GEAs has proposed that the nature and role of consensus in such processes are critical, distinctive parts of their "institutional epistemology" and that consensus can be thought of as a process, enabling diversity and broad representation, or a product, that is, scientific agreement about a common evidence base (Borie et al. 2021). Here we contribute to this literature by exploring how consensus was reached in the WCD.
First, we show how the WCD achieved a consensus that extended beyond the spectrum of consensus in previously studied GEAs. Borie et al. (2021) distinguish between "consensus-as-product" (a report that represents the minimum on which all parties can agree, as in the IPCC) and "consensus-asprocess," which reflects the inclusion of a wide or complete range of potentially conflicting views or expert opinions into agreement (as in the IPBES). While the literature on institutional epistemologies is primarily concerned with consensus about (scientific) evidence, political scientists have long investigated consensus as a tool or precondition for political action (e.g., Lijphart 2012). Although most political action is not linked to specific evidence, GEAs collate evidence with the aim of informing governmental and international policy, making the question of whether a consensus reached in a GEA extends to consensus about subsequent policy-an important one. Reaching consensus on evidence demands technical processes of aggregation, simplification, clarification, and/or specification (e.g., De Pryck 2021), while reaching consensus on political action or policy has characteristics more akin to political negotiations (e.g., Heisenberg 2005).
Consensus on policy direction can be considered as the most ambitious goal for a GEA. Extending the level of agreement in this way may come with trade-offs, however. Borie et al. (2021) note that consensus-as-product may lead agreement to cover less ground and represent fewer perspectives than consensus-as-process. We suggest that consensus on policy principles can be thought of as an even more brittle type of consensus, possibly only achievable under certain conditions, as in the case of the WCD. One may also hypothesize that consensus about evidence requires shared learning, while consensus about evidence-informed political action may be reached through bargaining.
Second, we identify a series of factors that shape the opportunities for reaching consensus in GEAs. While reaching consensus on policy principles is difficult, the presence of certain enabling conditions may make it more likely. While a full list of enabling conditions is yet to be established, we have identified a series of factors that led to success in the case of the WCD and that deserve further attention in the context of other international fora. The enabling conditions we have identified from our interviews (the historical context, the weak representational mandate, political skill and leadership, the time horizon) can be thought of as "ingredients" that facilitated consensus. The WCD shows that a consensus, even in the face of entrenched disagreement, does not necessarily require relatively homogenous groups of participants (such as climate scientists, in the case of the IPCC).
From the findings of a single case study, it is not possible to be certain how the individual enabling conditions relate to the consensus or, indeed, whether they should be thought of as "causal variables" (in a more postpositivist framing). Such more definitive statements would require comparative analysis of a range of cases. A case study using semistructured interviews can, however, offer "additional way[s] of adding granular appreciation of causal mechanisms," in line with the growing appreciation for transdisciplinary methods in GEP (O'Neill and Haas 2019, 8). Nevertheless, the potentially most suitable framework of comparison from a quantitative point of view is the review of collaborative governance by Ansell and Gash (2008), which draws on 137 cases. Our findings are partially in line with their previous hypotheses, namely, with regard to the role of political skill and leadership and the historical context.
With regard to the historical context, our findings follow the model of Ansell and Gash (2008), who suggest that a prehistory of conflict can be one starting condition that makes a consensus more likely. This assumption also mirrors the proposition by Brinkerhoff (2002) that a partnership approach can be a rational response to a situation of conflict where no one actor is perceived to be in control. However, it is clear that on its own, this is insufficient as an explanation for reaching a consensus and that further enabling conditions need to coincide with it. Moreover, less tangible aspects, such as the motivation derived from carrying out the process in a uniquely inspiring context (in the case of the WCD, post-apartheid South Africa), have not been considered previously, and the case of the WCD may be instructive.
With regard to leadership, Ansell and Gash (2008) note that facilitative leadership is most likely to lead to successful collaborative governance between public and private partners. This contrasts with traditional notions of leadership in global environmental politics, where it is more commonly understood as the counterpart to "followership" (see Busby and Urpelainen 2020). While facilitative leaders (like Asmal and Steiner, in this case) seek to facilitate dialogue and cooperation, leaders in global environmental politics are more commonly understood as wishing to influence others to bring them closer to their own positions (Andresen and Agrawala 2002;Underdal 1994;Young 1991). Kopra (2020) finds that facilitative leadership in global environmental politics is understudied and potentially associated with non-Western countries. It is also worth noting that most global environmental politics literature on leadership considers "countries" as its unit of analysis, not individuals (Andonova and Mitchell 2010), perhaps due to the pervasive focus on global climate policy (e.g., Busby and Urpelainen 2020). The case of the WCD thus draws attention to the fact that facilitative leadership by individuals may not have been sufficiently considered thus far by global environmental politics scholars (besides being a plausible factor behind consensus).
Our findings on the importance of time in consensus making are ambivalent, simultaneously supporting and contradicting previous theoretical statements about their role. On one hand, commissioners felt that they spent "a lot" of time together, which contributed to establishing the trust required to develop a consensus. On the other hand, both Dingwerth (2007) and Ansell and Gash (2008) cite a lack of time as an obstacle for consensus building, and it is thus surprising how persistently interviewees mentioned the WCD's short time horizon as a crucial contributing factor explaining its consensus. Here our findings suggest that urgency has not been sufficiently considered as an enabling condition for consensus making. A short time horizon may also have an impact on the personal profiles and circumstances of GEA support staff, for example, through creating a flat hierarchy in which there are no "senior colleagues" who may naturally dominate a workplace, again facilitating consensus making. In the case of the WCD, it is clear that the WCD Secretariat staff had an important role in shaping (and sharing) the WCD consensus.
In their analysis of global environmental standard-setting organizations (whose mandates thus have some parallels with the WCD), Boström and Tamm Hallström (2010) found that short time horizons tend to benefit some stakeholder groups over others. In particular, nongovernmental organizations were more attuned to this mode of working, associated with high pressure, scarce financial resources, and symbolic actions, while industry tended to prefer long-term engagement and a focus on technical aspects. Stakeholder dynamics inside the WCD mirrored this general pattern. While global civil society provided extremely well-coordinated input into the WCD, the dams industry lagged behind, despite the strong personal commitment of Veltrop, who may have been an atypical representative of industry. This may explain why the WCD consensus was broadly welcomed by civil society organizations and had a more mixed response among the dam-building industry.
This effortful and costly approach to consensus making, which imposed heavy workloads and stress on WCD staff, associated with the final report's looming deadline, had implications for external reception of their work. The strong personal investment of the ingroup of commissioners and staff generated strong commitment to the WCD consensus. However, this created a barrier to acceptance of its report by those on the outside, who had not undergone the same process of consensus-building transformation. As also noted by Dubash et al. (2001) and Dingwerth (2007), the WCD consensus extended to the relatively small group of commissioners only; even the WCD Stakeholder Forum did not form part of the ingroup.
This form of "weak representation" can thus be thought of as another enabling condition. While Dubash et al. (2001) and Dingwerth (2007) frame this as a limitation or even a potential flaw of the WCD consensus, one may thus also consider it a necessary precondition for reaching a consensus in the first place. The report's reception by external actors was mixed, with acceptance by some organizations and national governments and rejection or distancing by others (e.g., Germany endorsed the Dams and Development report in its policies, while the World Bank did not; Schulz and Adams 2019). The WCD's experience therefore suggests a dilemma for the design of global environmental assessment processes. The more inclusive or diverse participant selection is (in terms of background, training, geography, sector, interests), the more challenging it becomes to replicate a consensus in external settings. There is a potential trade-off between inclusiveness in the consensus-making forum and the subsequent impact of that consensus in the wider world.
This finding also extends research on the relationship between diversity, representation, and consensus in GEAs (e.g., Borie and Hulme 2015;Borie et al. 2021), which had suggested that strong diversity may reduce the likelihood for full consensus on evidence, whereas relatively homogenous groups of scientists are more likely to produce a consensus product. Weak representation emerges as a third alternative to enable the compilation of a consensus product despite strong diversity.

Conclusions
The final consensus product of the WCD, its final report, Dams and Development ( WCD 2000), sought to provide an authoritative summary of knowledge on dams and a list of policy recommendations and principles for dam planning. Despite the high profile of its launch, the report did not receive universal support, either by commentators or by dam building agencies, and implementation of its recommendations has since been patchy at best (Schulz and Adams 2019). Yet, remarkably perhaps, Dams and Development continues to be endorsed by commissioners and their staff. One commissioner commented, "It was a great achievement that we could at least sign a unanimous report. … The report is more balanced, much more balanced than anyone would expect." Yet, both supporters and critics have suggested that in terms of knowledge, the report's most significant contribution lay in getting agreement to overtly discuss the negative social and environmental impacts of large dams (Schulz and Adams 2019).
Political theory suggests that consensus products may hide disagreements among those participating, or "winners" and "losers," due to processes of bargaining rather than collective learning in their creation (Dingwerth 2007;Heisenberg 2005). Dingwerth (2007) also suggests that a consensus approach may obscure power imbalances and exclude more critical or confrontational voices, cementing a mainstream status quo (though we find that neither applies to the WCD, where dam-critical voices were able to challenge the status quo). Bargaining may be more likely with regard to consensus about political action, where participants may have stronger existing preferences, as opposed to consensus about evidence, where shared learning would be a more natural strategy.
Although one member of the WCD Secretariat supported the view that the WCD report was the result of one side "winning," comparing the WCD with a "World Commission on Slavery" to solve slavery (where it would be inconceivable that supporters and opponents come to a consensus, except if one side can "win" over the other through successful bargaining), commissioners did not have this perspective. Only one commissioner expressed minor regret about signing off on the report; they felt it might have been more impactful had it not called for the free, prior, and informed consent (FPIC) of Indigenous peoples affected by dam construction. This issue was consistently singled out as the most hotly debated among commissioners and the only one where it might be said that sides were taken and one side "won." At the time, FPIC was also a highly controversial issue in the World Bank, which subsequently declined to formally incorporate WCD guidelines (with its commitment to FPIC) into its safeguard policies.
In the light of the ongoing disputes about the environmental and social impacts of large dams, the WCD's consensus about policy recommendations is in many ways remarkable, as is the continued relevance of the analysis it conducted (Schulz and Adams 2019). Our interviews show that its consensus emerged from a process of shared learning around an evidence base, by a group of committed people, ably led and increasingly trusting of each other. Of course, memory bias may have eliminated negative memories of bargaining between commissioners, but the experience of the WCD suggests that evidence-based policy is not just a theoretical ideal and that-under the right conditionsconsensus within a commission-like group is possible, even if it proves harder to persuade outside actors of its merits.
Christopher Schulz is a lecturer in the School of Geography and Sustainable Development at the University of St Andrews, United Kingdom. Previously he was a research associate in the Department of Geography at the University of Cambridge, United Kingdom, where he conducted research on the history, legacies, and impact of the World Commission on Dams. His research interests include questions of environment and development, environmental values, and water governance. Most of his previous research has been in Latin America, but he has also worked in South Asia and Africa.
Bill Adams is a geographer whose work focuses on issues of sustainability and conservation from the perspectives of political ecology and environmental history. He has a long-standing interest in the environmental and social impacts of dams, particularly in Africa. His books include Wasting the Rain: Rivers, People and Planning in Africa (Earthscan, 1992) and Green Development: Environment and Sustainability in a Developing World (4th ed., Routledge, 2020). He held the Moran Chair in Conservation and Development from 2006 to 2020 in the Department of Geography at the University of Cambridge, United Kingdom, and is currently Claudio Segré Professor of Conservation, Graduate Institute, Geneva, Switzerland.