Citation: Sheffield, D.; Butler, C.W.; Richardson, M. Improving Nature Connectedness in Adults: A Meta-Analysis, Review and Agenda. Sustainability 2022, 14, 12494. https://doi.org/10.3390/su141912494 Academic Editors: Thomas Astell-Burt and Dianne A. Vella-Brodrick Received: 31 July 2022 Accepted: 16 September 2022 Published: 30 September 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). sustainability Review Improving Nature Connectedness in Adults: A Meta-Analysis, Review and Agenda David Sheffield * , Carly W. Butler and Miles Richardson School of Psychology, University of Derby, Derby DE22 1GB, UK * Correspondence: d.sheffield@derby.ac.uk; Tel.: +44-(0)-7825904935 Abstract: With clear links between an individual’s sense of nature connectedness, their psychological wellbeing, and engagement in nature-friendly behaviours, efforts to improve people’s relationships with nature can help unite human and planetary wellbeing. In the context of a rapidly growing evidence base, this paper updates previous meta-analytic reviews to explore the impact of (quasi-) experimental manipulations and field interventions on nature connectedness in adult populations. The analysis examines the relative effects of type of contact (direct or indirect), quality of engagement (active or passive) and the timing of the engagement (single session, repeated practice or residential). Results show a medium positive short-term mean effect of manipulations on nature connectedness, with similar effect sizes for immediate and sustained increases. No effect size differences were observed between different types of contact, quality, or timing of engagement. Follow-up measures were mostly used in studies involving regular and repeated practices. An agenda for future research and practice is put forward, emphasising the need for examining a wider range of nature engagement activities, greater understanding of factors leading to increases in nature connectedness, design and testing of practices for sustained nature connection, and initiatives that engage people with nature, create conditions for nature connection, and encourage repeated nature engagement activities. Keywords: nature connectedness; nature relatedness; interventions; sustained change; meta-analysis 1. Introduction There is global recognition that fostering closer connections with nature offers a solution to the joint issues of nature degradation, climate change, and human illbeing. Calls for restoring the human–nature relationship to address the nature and climate emergencies are growing in number and volume, with organisations like the United Nations [1] and World Economic Forum [2] highlighting the urgency and necessity of fixing our relationship with nature. While many solutions will target deeper leverage points at the national and global level, there is a need for parallel efforts to help individuals and communities feel closer to nature to create environments for thriving. The subjective sense of feeling closer to nature is a key element of nature connectedness—a psychological construct that reflects how people think about, feel about, and relate to nature. Nature connectedness provides a useful and measurable focus in efforts to re- new the human–nature relationship and is noted as a key realm for transformational sustainability interventions [3,4]. The applied potential of nature connectedness inter- ventions to improve the human–nature relationship through applying the pathways to nature connectedness [5,6] is supported by recent evidence reviews [7]. This interest in nature connectedness stems from a strong and robust link with pro-environmental be- haviours, pro-nature conservation behaviour [8,9], and a greater sense of well-being to levels above accepted benchmarks such as socioeconomic status [10–12]. Research also suggests a distinction between passive nature contact and nature connectedness, with nature connectedness being more important than number of visits to nature or time in nature in predicting wellbeing and engagement in pro-environmental behaviours [11,13]. Sustainability 2022, 14, 12494. https://doi.org/10.3390/su141912494 https://www.mdpi.com/journal/sustainability