Integrating Artificial Urban Wetlands Into Communities: A Pathway to Carbon Zero?

In their natural state, wetland ecosystems provide an optimum natural environment for the sequestration and long-term storage of carbon dioxide (CO2) from the atmosphere. The loss of wetlands under advancing urbanization not only diminishes this capacity for storage, but increases methane and greenhouse gases as the land is disturbed. Nevertheless, there is growing scientific interest in using artificial or constructed wetlands as a way to mitigate the impact of global climate change, with most attention on their use for water management. Using a potential integrated urban wetland site in Glasgow as a case study, this paper critically examines how artificial urban wetlands can contribute to urban net zero targets in terms of their ability for carbon sequestration, and as part of sustainability initiatives more broadly. We find there are several barriers to implementing artificial urban wetlands for carbon drawdown alone, in particular regarding land ownership constraints, uncertainties in capture efficacy and capture quantitation, and eligibility for market-based crediting schemes. These issues make it currently challenging for the carbon reduction contribution of urban wetlands to be quantified and, say, certified to generate revenue to communities through market-based carbon crediting. However, if integrated within wider community-based sustainability initiatives, artificial urban wetlands can support multiple dimensions of sustainability, creating or supporting value far beyond water management and carbon sequestration objectives. Potential co-benefits range from areas such as health and wellbeing, biodiversity, education, food security, behavioural changes, and social care. Our findings show that for these co-benefits to be identified, maximised and realised, a place-based approach to urban wetland development must be adopted, engaging stakeholders from the project outset to define and facilitate collaboration towards shared outcomes for society, community, and environment. These findings will be relevant to any urban infrastructure development seeking to meet sustainability goals beyond carbon capture.

Alerta roja para los humedales urbanos

Last November 17th, a fire started by a flare, laid waste to 10 ha of the Paicavi urban wetland in Concepción, which is part of the larger Rocuant-Andalién water system. The incident once again raised a red flag for these green spaces, which have been left behind in Chilean urban management and planning in recent decades, on not having been acknowledged as urban green infrastructure, or as part of a broader environmental matrix.

Ecosystem Services Monitoring in the Muthurajawela Marsh and Negombo Lagoon, Sri Lanka, for Sustainable Landscape Planning

In this study, we examined the impacts of urbanization on the natural landscape and ecosystem services of the Muthurajawela Marsh and Negombo Lagoon (MMNL) located in the Colombo Metropolitan Region, Sri Lanka, with the goal to help inform sustainable landscape and urban planning. The MMNL is an important urban wetland ecosystem in the country but has been under the immense pressure of urbanization where the natural cover (e.g., marshland and mangrove areas) is continuously being converted to urban use (e.g., residential and commercial). Here, we estimated and assessed the changes in the ecosystem service value (ESV) of the MMNL based on land use/cover (LUC) changes over the past two decades (1997–2017). Considering two plausible scenarios, namely a business-as-usual (BAU) scenario and ecological protection (EP) scenario, and using a spatially explicit land change model, we simulated the future (2030) LUC changes in the area and estimated the potential consequent future changes in the ESV of the MMNL. The results revealed that from 1997 to 2017, the ESV of the MMNL decreased by USD 8.96 million/year (LKR 1642 million/year), or about 33%, primarily due to the loss of mangrove and marshland from urban expansion. Under a BAU scenario, by 2030, it would continue to decrease by USD 6.01 million/year (LKR 1101 million/year), or about 34%. Under an EP scenario, the projected decrease would be lower at USD 4.79 million/year (LKR 878 million/year), or about 27%. Among the ecosystem services of the MMNL that have been, and would be, affected the most are flood attenuation, industrial wastewater treatment, agriculture production, and support to downstream fisheries (fish breeding and nursery). Overall, between the two scenarios, the EP scenario is the more desirable for the sustainability of the MMNL. It can help flatten its curve of continuous ecological degradation; hence, it should be considered by local government planners and decision-makers. In general, the approach employed is adaptable and applicable to other urban wetland ecosystems in the country and the rest of the world.

The Temporal Variation of the Microclimate and Human Thermal Comfort in Urban Wetland Parks: A Case Study of Xixi National Wetland Park, China

As an important part of the ecological infrastructure in urban areas, urban wetland parks have the significant ecological function of relieving the discomfort of people during their outdoor activities. In recent years, the specific structures and ecosystem services of urban wetland parks have been investigated from different perspectives. However, the microclimate and human thermal comfort (HTC) of urban wetland parks have rarely been discussed. In particular, the changing trends of HTC in different seasons and times have not been effectively presented. Accordingly, in this research, a monitoring platform was established in Xixi National Wetland Park, China, to continually monitor its microclimate in the long term. Via a comparison with a control site in the downtown area of Hangzhou, China, the temporal variations of the microclimate and HTC in the urban wetland park are quantified, and suggestions for clothing are also provided. The results of this study demonstrate that urban wetland parks can mitigate the heat island effect and dry island effect in summer. In addition, urban wetland parks can provide ecological services at midday during winter to mitigate the cold island effect. More importantly, urban wetland parks are found to exhibit their best performance in improving HTC during the daytime of the hot season and the midday period of the cold season. Finally, the findings of this study suggest that citizens should take protective measures and enjoy their activities in the morning, evening, or at night, not at midday in hot weather. Moreover, extra layers are suggested to be worn before going to urban wetland parks at night in cold weather, and recreational activities involving accommodation are not recommended. These findings provide not only basic scientific data for the assessment of the management and ecological health value of Xixi National Wetland Park and other urban wetland parks with subtropical monsoon climates, but also a reference for visitor timing and clothing suggestions for recreational activities.