Sustainable Design of Urban Rooftop Food-Energy-Land Nexus

Comparative analysis on the effectiveness of green roofs and photovoltaic panels as sustainable rooftop technologies

Photovoltaic (PV) panels and green roofs are considered as the most effective sustainable rooftop technologies at present, which utilizes the effective rooftop area of a building in a sustainable manner. To assess the most suitable rooftop technology out of the two, it is vital to have an idea on the energy savings potential of these sustainable rooftop technologies, alongside a financial feasibility analysis considering their overall life spans and additional ecosystem services. To achieve this objective, ten selected rooftops located in a tropical city were retrofitted with hypothetical PV panels and semi-intensive green roof scenarios to perform the present analysis. The energy-saving potential for PV panels was estimated with the assistance of PVsyst software, and green roof ecosystem services were evaluated through a range of empirical formulas. The financial feasibility of the two technologies was assessed by Payback Period and Net Present Value (NPV), through data obtained by local information sources such as solar panels and green roof manufacturers. The results indicate that PV panels achieve a rooftop PV potential of 244.39 KWh/yr/m2 during their 20-year life span. Furthermore, green roofs reach an energy-saving potential of 22.29 KWh/yr/m2 during a 50-year life span. Moreover, based on the financial feasibility analysis, PV panels demonstrated an average payback period of 3-4 years. Green roofs exemplified 17-18 years to recover their total investment for the selected case studies in Colombo, Sri Lanka. Although green roofs do not provide comparatively significant energy savings, these sustainable rooftop technologies aid in energy saving under different response intensities. In addition, green roofs offer several other ecosystem services that improve urban areas' quality of life. Collectively, these findings highlight the particular importance of each rooftop technology promoting building energy savings.

A Flashforward Look into Solutions for Fruit and Vegetable Production

One of the most important challenges facing current and future generations is how climate change and continuous population growth adversely affect food security. To address this, the food system needs a complete transformation where more is produced in non-optimal and space-limited areas while reducing negative environmental impacts. Fruits and vegetables, essential for human health, are high-value-added crops, which are grown in both greenhouses and open field environments. Here, we review potential practices to reduce the impact of climate variation and ecosystem damages on fruit and vegetable crop yield, as well as highlight current bottlenecks for indoor and outdoor agrosystems. To obtain sustainability, high-tech greenhouses are increasingly important and biotechnological means are becoming instrumental in designing the crops of tomorrow. We discuss key traits that need to be studied to improve agrosystem sustainability and fruit yield.

Satellite monitoring of shrinking cities on the globe and containment solutions

Shrinking cities are often neglected in the context of global urbanization, the tip of the iceberg that was driven by underlying complex sets of causes. Therefore, it is urgent and crucial to investigate the invisible aspects of global urbanization propelling specific challenges to attain Sustainable Development Goal 11 (SDG 11) related to sustainable cities and communities. Here, we identify shrinking cities in 1992-2000, 2000-2012, and 2013-2018 and predict them in 2018-2050, using nighttime light images and redefined natural city boundaries. The proportion of shrinking cities increased from 9% to 16 and 25%. Looking ahead, there will be 7,166 predicted shrinking cities in 2050, accounting for 37% of all cities. In this context, synergistic efforts like regreening vacant lands and constructing compact cities would help achieve SDG 11 in consideration of the new urban shrinking landscape with multisource data like CO₂ emissions and points of interests (POIs).