Urban areas are expanding due to rural-urban migration and due to population increases. Their resilience is being challenged due to socio-political consequences of increasingly frequent and severe storms, due to climate changes, influx of human and animal refugees and as a consequence of the COVID-19 pandemic. The authors prepared a systematic literature of ways cities can be transformed into more resilient, and sustainable regions by creatively enhancing the quality and quantity of blue and green areas in and around them. The literature review was conducted to provide holistic insights into selection, implementation monitoring, assessment, and valuation of Nature-based Solutions in diverse urban regions. The authors reviewed no fewer than 298 articles from 109 academic journals and related sources, published within 1997-2020. The focus of the articles was upon 'nature-based' changes that are being implemented in urban areas, globally to enhance their resilience and the 'quality-of-life' of humans and other species. By implementing nature-based solutions, and complimentary 'urban wilding' approaches, urban areas and their hinterlands are expanding their 'blue' and 'green' areas and are thereby decreasing the 'heat-island' effects, while improving human health by surrounding them with rich bio-diversities of locally adapted, aquatic and terrestrial plants and animals. Although, many NBS options have been documented to be beneficial, their environmental, economic and social/psychological dimensions have not been adequately quantified, especially in the context of climate changes, and with regard to COVID-19. It is essential that the benefits of NBS are quantified with easily measurable outcomes, that are readily understood by practitioners, city policy-makers and members of community organizations, based upon specific geographical and climatological contexts. This will help them accelerate implementation of NBS and wilding into their urban systems. The reviewers found that more research is needed on anticipatory learning, backcasting and community participation to help to effectively implement the appropriate NBS for improving the sustainability of urban systems. The reviewers provide guidance for urban leaders to incorporate NBS into their policies and strategies to improve urban resilience and equity and to more effectively reduce impacts of climate change, population growth and pandemics. (C) 2020 Elsevier Ltd. All rights reserved.