Geoforum 132 (2022) 154–161 Available online 21 December 2021 0016-7185/© 2021 Elsevier Ltd. All rights reserved. Introduction to themed issue: Ignorance and uncertainty in environmental decision-making Trevor Birkenholtz a, * , Gregory Simon b a Pennsylvania State University, University Park, PA 16802, USA b University of Colorado, Denver, CO 80217, USA A R T I C L E INFO Keywords: Environmental Governance Ignorance Knowledge Political Ecology Uncertainty ABSTRACT There is growing scholarly engagement with the role of uncertainty in questions of environmental decision- making. Yet ignorance, while prevalent in the STS literature, has received less attention in geography and cognate disciplines. In our introduction to this special collection, we review the literature on ignorance and uncertainty to make two contributions. First, we engage each concept to demonstrate that, in general, ignorance is a ‘lack of knowledge’ (or the appearance of lack of knowledge) while uncertainty is a ‘lack of knowledge clarity’ (or the appearance of lack of knowledge clarity). Second, we argue that while it is useful for theory building to distinguish between the two concepts, it is helpful also to view them as interrelated and processual. We demonstrate this relationality and the different forms it takes by introducing a process-based typology: ignorance and uncertainty as outcome; ignorance and uncertainty as resource; and ignorance and uncertainty as obstacle. The six papers in the collection offer a diverse set of engagements with ignorance and uncertainty including grounded case-studies and theoretical interventions focused on environmental decision-making. 1. Introduction The production, contestation and legitimation of environmental knowledge has been a longstanding concern in geography and cognate felds (Davis, 2005; Birkenholtz, 2008; Goldman et al., 2011; Forsyth, 2015; Simon and Peterson, 2019). Scholarly engagements with envi- ronmental knowledge range widely from exploring how we understand and frame the global environmental crisis (Shrivastava et al., 2020) to challenging scientifc paradigms and techno-economic reason. Embedded within this work are case-study descriptions of the challenges emerging from sincere debates about knowledge and expertise as well as those that dissect instances of intentional obfuscation (Neimark et al., 2019; Schmitt and Li, 2019). As Proctor (2008) notes, we seem to “know a lot about knowledge.” Indeed, “epistemology is serious business” (Proctor 2008 1). This commitment to studying environmental knowl- edge certainly makes sense considering that data and knowledge interact recursively with beliefs and values and, ultimately, decision- making. The relationship between what we know and what we do has thus fgured centrally as a motivating factor for theory building and policy evaluation within geography and allied felds (Senanayake and King, 2021). If we tend to know a lot about knowledge, however, we seem to know much less about ignorance and uncertainty, particularly in the realm of environmental decision-making. This is not meant to suggest that the study of ignorance and uncertainty lacks valuable contributions. Over the past 20 years there has been a steady increase in studies exploring these subjects as they relate to environmental and social topics (see e.g., Proctor and Schiebinger, 2008; Hess, 2020; Gross and McGoey, 2015; Kleinman and Suryanarayanan, 2013; Senanayake and King, 2021; Scoones and Stirling, 2020; Frickel et al., 2010) These and other con- tributions have generated valuable insights about the causes, nature and implications of not-knowing, of working with incomplete and fawed knowledge, and of the machinations of producing and understanding mis-information. And yet, while informative, our assessment reveals a feld that at times seems ambiguous and diffcult to assess due to overlapping and divergent terminologies, meanings and reference points (see also Gross, 2007). For example, while the terms ignorance and uncertainty will frame this review, a litany of other terms have been used to describe a general lack of knowledge and/or clarity about social-environmental change. These include terms such as knowledge absence, ambiguity, forgotten knowledge, imperceptibility, incomplete knowledge, non- * Corresponding author. E-mail addresses: tlb5964@psu.edu (T. Birkenholtz), gregory.simon@ucdenver.edu (G. Simon). Contents lists available at ScienceDirect Geoforum journal homepage: www.elsevier.com/locate/geoforum https://doi.org/10.1016/j.geoforum.2021.12.003