With nearly 70% of the world population expected to live in cities by 2050, assessing the sustainability of urban systems, both existing and future ones, is becoming increasingly relevant. Making cities more sustainable is a global priority, which is highlighted by ‘Sustainable Cities and Communities’ being listed as one of the Sustainable Development Goals (SDG) adopted by United Nations Member States in 2015. This Virtual Special Issue (VSI) explores the implementation and assessment of policies and technologies that contribute to the transition to a sustainable, energy efficient and regenerative society. We organized the issue according to four main research themes: 1) Renewable Energy Systems (i.e., different types of systems, qualitative assessments and public acceptance); 2) Sustainable Built Environment (which includes construction, operation and refurbishment); 3) Multi-Scale Models (considering urban sustainability transition from building to districts, or cities and regions to multi-country comparisons and their scaling across different countries); and 4) Governance and Policy (climate change mitigation and adaptation plans/policies that are reported across countries, urban services and infrastructures).

This paper serves two purposes. The first is to provide an analysis about patterns, correlations and synergies found across the different topics that have been addressed over the last 20 years in the literature about cities’ sustainability paths. A bibliometric analysis and a contingency matrix show the degree of correlation between scientific journals and main topics addressed by published articles. Secondly, the paper acts as an Editorial to the VSI, introducing the wealth of research articles and topics included in it. Both the bibliometric analysis and the papers published in this VSI demonstrate the interconnectedness of energy consumption, pollutant emissions and the competition for finite resources. The aim is to present advances and challenges of this exciting and ever-evolving research field to inform and guide future studies of urban sustainability.

到2050年，预计将有近70％的世界人口居住在城市中，评估现有和未来城市系统的可持续性变得越来越重要。使城市更具可持续性是全球优先事项，“可持续城市与社区”强调了这一点被列为联合国会员国于2015年通过的可持续发展目标（SDG）之一。该虚拟特刊（VSI）探索和实施有助于推动向可持续，节能和可再生能源过渡的政策和技术的评估社会。我们根据四个主要研究主题组织了本期杂志：1）可再生能源系统（即，不同类型的系统，定性评估和公众认可）；2）可持续建筑环境（包括建筑，运营和翻新）；3）多尺度模型（考虑城市可持续性从建筑向地区，城市和地区的过渡到多国比较以及它们在不同国家之间的扩展）；

本文有两个目的。首先是对过去20年来有关城市可持续性发展路径的文献中涉及的不同主题的模式，相关性和协同作用进行分析。文献计量分析和列联矩阵显示科学期刊与已发表文章所涉及的主要主题之间的相关程度。其次，本文是VSI的社论，介绍了其中包含的大量研究文章和主题。文献计量分析和在该VSI中发表的论文都证明了能源消耗，污染物排放和有限资源竞争的相互联系。