Water scarcity and accessibility remain persistently amongst the most prominent global challenges. Although there is a wide agreement among international organizations that Integrated Water Resources Management (IWRM) and water governance are key to overcome water-related challenges, global assessments of the progress made by cities is lacking. This paper for the first time analyses the challenges of water, wastewater, municipal solid waste and climate change in cities. We used empirical studies (125 cities) based on the City Blueprint Approach and developed a statistical estimation model to estimate IWRM performances of another 75 cities. These 200 cities in total represent more than 95% of the global urban population. This comprehensive global picture enables us to evaluate the existing gaps in achieving water-related Sustainable Development Goals (SDGs), in particular SDG 6 (clean water and sanitation) and SDG 11 (sustainable cities and communities). The best performing cities were Amsterdam and Singapore. Unfortunately, most cities do not yet manage their water resources wisely and are far from achieving the SDGs. For instance, targets regarding drinking water supply are still a challenge for many cities in Africa and Asia and challenges regarding sanitation are high in cities in Africa, Asia and Latin America. The same holds for solid waste management, climate adaptation, and people living in informal settlements. In another paper we will address the solution pathways to these global challenges.

Though we are in urgent need of environmental warnings to slow environmental deterioration, currently, there is no internationally concise method for environmental warnings. In addition, the existing approaches do not combine the three aspects of ecology, resources, and environment. At the same time, the three elements of the environment (air, water, and soil) are separated in most environmental warning systems. Thus, the method this paper gives is an innovative attempt and aims to make environmental assessment more practical. This paper establishes the index system of an environmental early warning based on the Driving–Pressure–State–Influence–Response (DPSIR) model. The Analytic Hierarchy Process (AHP) method was used to determine the weights. Next, single and integrated index methods further assess the environmental warning state, in which the weighted summation method is used to summarize the data and results. The case of Tianjin is used to confirm the applicability of this method. In conclusion, the method in this paper is more well-behaved and, therefore, more suitable to assist cities in their environmental assessment.

The construction of ecological barriers and ecological security patterns is an important way of maintaining regional ecological security in landscape ecology. However, there is still no consensus on the concept and connotation of ecological barriers, and the zoning and adaptive management of ecological sources are rarely considered in the construction of ecological security patterns. This study uses the terrestrial ecosystem of Bohai Bay, China as a study area, and the identification and zoning of ecological sources in the ecological security pattern are achieved by combining an ecosystem service assessment with an ecological risk assessment, and on this basis, ecological barriers are identified to optimize the structure and function of ecological sources. The minimum cumulative resistance model is used to identify ecological corridors and ecological strategic nodes and to construct an ecological security pattern based on the modified ecological sources. The results demonstrate that firstly, 2873.25 km² was identified as the ecological source, accounting for 14.28% of the total. Secondly, there are three large ecological barrier zones and nine ecological barrier cells with a total area of 1173.06 km², accounting for 40.83% of the ecological sources. Thirdly, a total of 35 ecological corridors were extracted, and 32 ecological strategic nodes were marked, mainly distributed at the intersection and branches of important ecological corridors. An ecological security pattern construction system was formed with the collection of ecological source selection, ecological barrier identification, ecological resistance surface construction, and ecological corridor extraction. Fourthly, the concept and connotation of ecological barriers was analyzed, and the complementary relationship between ecological barriers and ecological security patterns in terms of structure and function is discussed. This study enriches the definition and connotation of ecological barriers, provides a new framework for identifying the ecological security patterns, and provides scientific guidance for ecological protection and management in coastal areas.