Climate change is already taking place all over the world [1], with the most significant impacts being rising temperatures, changes in rainfall patterns and an increasing number of extreme weather events [2]. Urban areas are particularly vulnerable due to the concentration of population, infrastructure, and property [1]. The most impacted regions are located in the developing world [2], despite the global north being responsible for approximately 92% of all GHG emissions [3]. The impacts are accelerating, as stated in the latest IPCC report [2], with tipping points being reached and not enough action being taken by governments. While we are facing scenarios of substantial increase in temperatures, even moderate levels of warming can have catastrophic consequences [4]. The biodiversity crisis is interlinked with climate change, manifesting itself in the sixth mass extinction of life on the planet [5].

NbS have been increasingly recommended for urban adaptation and as an alternative to traditional urban infrastructure [6,7,8,9]. The term “Nature-based Solutions” was first mentioned in a World Bank report from 2008 [10,11] listing projects addressing the biodiversity and climate crises, with a particular focus on adaptation and vulnerable communities. The International Union for Conservation of Nature (IUCN) describes NbS as actions that protect, sustainably manage, and restore natural or modified ecosystems, while simultaneously providing benefits for human wellbeing and biodiversity [12]. The European Commission (EC) has a broader definition, considering NbS to be solutions that are inspired and supported by nature, which are cost-effective and simultaneously provide environmental, social, and economic benefits while contributing to build resilience [13]. As the concept of NbS is quite recent, substantial knowledge gaps remain, including how to support its relevance for urban areas [1]. There are also barriers to its implementation that must be understood to be overcome. The objective of this review is to contribute to the assessment of the dimension of the challenges, identifying opportunities, barriers, and knowledge gaps in the use of NbS for implementation in an urban context. The applied review methodology …