Departmental Research Output Prize 2022

This study presents a pioneer attempt to embed Nature-based Solutions (NbS) into the quantification of social cost of carbon in order to adequately capture the impacts of NbS and specify feasible NbS strategy, taking into account the interactive and complex dynamics of land-use changes. It sheds important insights into the effectiveness of various NbS, and offers practical implications for policy-makers to devise comprehensive policies covering all feasible CO2 abatement options.

This article provides insights into the interaction between urban greenness and mixed land-use, two key dimensions defining urban liveability, in shaping citizens’ life satisfaction. The empirical findings of this study shed better understanding in the nexus between urban built environment and life satisfaction and provide input for policy-makers on how to improve urban liveability of Chinese cities.

This piece closes a forum on the spatiality and political utility of humor, responding to developments in this arena in three main areas, with the sobering contemporary reality of a comedian-president facing down a brutal invasion serving as a critical, conjunctural point of entry. First, I follow others in highlighting the fact that humor can be extremely serious business in many different ways. Second, as I illustrate through examples, context—perhaps especially geographical context—matters for both the study and the exercise of humor. Third, I suggest several promising avenues for future research and practice. This piece draws on both extensive ethnographic research in contemporary Mexico City as well as an analysis of the contours, commentaries, and nascent trajectories of a burgeoning literature on the spatiality and politics of humor within and beyond human geography.

This paper advanced tourism theory by moving beyond Western understandings unable to account for tourism’s contemporary diversity. Travel is often motivated by a range of desires and social obligations as well as leisure pursuits. Conventional Western understandings of tourism provide little consideration for the extent to which culture, community and traditional obligations are key motivators for tourism mobility. A concurrent mixed methods design of surveys supplemented by interviews with both urban and rural Samoans was employed. Samoan understandings of tourism are expressed via the concept of malaga, which has a range of meanings including ‘migration’, ‘movement’ or ‘travel back and forth’. For Samoans, travel was for cultural and familial purposes, including the maintenance of cultural bonds through fa’alavelave (traditional obligations) and visiting friends and relatives. This paper advances knowledge of Samoan forms of travel and tourism mobility which are deeply connected to other forms of mobility, social structures and culture. It provided important insights into the travel practices of a Pacific Islander people at a time when the South Pacific is becoming a site of intensifying geopolitical competition.

While access to veterinary services is vital to the welfare of pets and their owners, few studied the spatial accessibility of veterinary services. This study, as a pioneering study, examined the spatial-temporal accessibility of veterinary service and how it is associated with social and spatial inequality in Hong Kong. We measured the spatial availability and accessibility of both general and 24/7 veterinary clinics using GIS and principal component analysis. We found a large social, spatial, and spatial-temporal inequality in access to veterinary services across the city, favorable to the communities with wealthier households and highly educated populations. We also argue that need-based veterinary support intends to target remote rural areas while overlooking new growth areas close to the traditional urban core but poor in accessibility to veterinary care (128 words).

Despite ever-increasing public and financial support for public transportation in recent decades, transit ridership has dropped substantially in the 2010s across the United States. While many theories that explain the reasons behind the decline in ridership have been proposed, no consensus on the primary causes has been reached. In response, we employ a novel combination of methods, gradient boosting decision tree and counterfactual simulations, to examine the complex relationships between transit ridership and key internal and external factors from 2002 to 2017 in 85 of the largest urbanized areas in the U.S. Among several contributing factors, the declining cost of driving, measured by the decreasing share of carless households combined with lower gasoline prices, was the salient, most influential factor behind the recent decline. Neighborhood change in high-density neighborhoods also led to a moderate net loss in ridership. The only factor that has been mitigating further decline was an increase in transit services. Had this increase not occurred, loss of ridership would have been more than double the actual loss during the study period. In short, this study provides valuable insights into the recent declining trends in transit ridership and rich implications to transit planning and policy.

The novelty of this paper lies in its insights of work-from-home (WFH) arrangement on urban traffic congestion beyond broad city-scale analysis. Methodologically, we use weekday hourly traffic data covering January 2019 to July 2021 to examine the impact during three distinct periods. The findings caution against the optimism that WFH can relieve urban transport problems despite jobs-housing imbalance. While the WFH arrangement has potentials to ease commuting congestion, future e-working and transport measures need to take spatial and temporal dimensions into account.

This paper is the first of its kind in systematically analysing 38 construction projects in Hong Kong, spanning a substantial period of twenty years. Specific project details in relation to sustainability performance have been extracted for compiling the sustainability indicators. The results point the higher sustainability of construction methodologies with increasing construction modularity. The paper is of high value in informing policy-makers about enhancing construction sustainability.

This study generated a global land surface fraction of absorbed photosynthetically active radiation (FAPAR) product with a 250  m resolution based on a deep learning model from MODIS time series of observation information. Direct validation and intercomparison revealed that our product better meets user requirements and has a greater spatiotemporal continuity than other existing products. To our knowledge, this is the first global time-series FAPAR product at the 250-m spatial resolution that is freely available to the public (www.geodata.cn and www.glass.umd.edu).

Carbon dioxide (CO2) emissions from artificial reservoirs represent a key component of the global carbon budget. However, current estimates are still poorly known due to spatial underrepresentation of reservoir CO2 emissions (FCO2) and lack of temporally resolved measurements. In this study, we performed high-resolution, continuous monitoring of FCO2 in a semiarid hard-water reservoir to examine its seasonal and diel variability. Although the reservoir is moderately to highly productive throughout the year, it is a net CO2 source with FCO2 values in the range of 308-1753 mg C m–2 d–1. This high CO2 efflux indicates that productive waters are not necessarily CO2 sinks. Both surface water CO2 partial pressure (pCO2) and FCO2 exhibit clear seasonal and diel variations. High CO2 efflux is observed during the ice-thaw period, and it indicates the release of CO2 that was accumulated during the winter. CO2 effluxes are typically higher during the nighttime driven by aquatic metabolism, but episodic weather events (e.g., rainfall and strong winds) can significantly enhance CO2 emissions and even reverse the diel pattern. Our study also shows that using only daytime measurements to estimate daily CO2 emission would underestimate it by 9-25%. Hence, future global assessments must incorporate CO2 emissions from hard-water reservoirs and account for their seasonal and diel variability.

In this paper we question to what extent individuals can learn during collaboration when distance between them increases. Indeed, there is little question that new communication and transportation technologies have effectively “shrunk the world” for a great many activities. At the same time, the “death of distance” has been greatly exaggerated, especially in fields such as academic scholarship and knowledge development where the positive benefits of knowledge spillovers remain highly distance dependent.
We analyze 17.6 million publications authored by 1.7 million scholars to examine how knowledge spillovers between scholars collaborating at different geographical distances impacts their future knowledge portfolios. We do this by employing a very specific sampling strategy that is able to tease out learning effects when combined with novel and advanced matching techniques and statistical modeling.
Our results show that in 1975, scholars collaborating locally were 57 % more likely to learn from knowledge spillovers than similar scholars collaborating non-locally. We identify four factors that structure these findings. Individuals deriving the greatest learning premiums from local collaboration tend to be (1) in earlier stages of their career; (2) associated with lower-ranked institutions; (3) working with fewer collaborators; and (4) in STEM fields. The probability of learning drops with geographical distance and correspond to the number of institutional boundaries crossed during collaboration. We conclude that even in the 21st century, geographical distance still negatively impacts knowledge spillovers through collaboration.
These findings have implications for debates in innovation and management studies concerning knowledge spillovers, the spatial organization of (knowledge-intensive) economic activity, regional innovation policies, structuring team-work and working-from-home vs. returning to office.

Environmental sustainability and footprints of global aquaculture. Resources, Conservation and Recycling, 180, 106183.Here, for the first time, we developed a food-energy-water-carbon (FEWC) composite sustainability index (0–100) to assess the sustainability of global aquaculture across countries. Results indicate that the overall sustainability of global aquaculture is low (average score = 26) with none achieving a high sustainability score (75–100) and almost all practicing aquaculture in a relatively low sustainable way (0–50). Considering the sub-sustainability at a sector level, 80% of countries had at least two sectors among FEWC falling into the low sustainable zone (score less than 25). Regarding the environmental impacts, global aquaculture production accounted for approximately 1765.2 × 103 TJ energy use, 122.6 km3 water consumption, and 261.3 million tonnes of greenhouse gas emissions in 2018. China led all countries by contributing to more than half of global aquaculture water consumption and greenhouse gas emissions, followed by India and Indonesia. This study highlights the significance of cross-sectoral management and policymaking to achieve global aquaculture sustainability.

This study presents the first scoping review of impacts of COVID-19 on the ocean-human system.From a geospatial perspective, the studies covered a total of 37 countries, mainly from Asia, Europe, and North America, with a particular focus on the Indian Ocean and the Mediterranean Sea. From an environmental perspective, both positive and negative effects on global oceans were summarized. Notably, improved coastal water quality and reduced underwater noise were reported. On the other hand, the increasing COVID-19-related medical waste such as personal protective equipment leads to severe pollution, which threatens the marine ecosystem and wildlife. From a socioeconomic perspective, the impacts of the pandemic were negative throughout with marine tourism and the fishery industry being severely disrupted. Coastal communities suffered from loss of income, unemployment, inequalities and health problems. The COVID-19 pandemic offers an opportunity for transformation of management and economic practices in order to save our ocean and boost progress towards Sustainable Development Goal 14 (SDG 14).

Urban tree species is the basis for studying the urban-environment coordination mechanism at the species level. Remote sensing provides a good foundation for the identification of urban tree species, nevertheless, various reasons make it challenging to recognize subtropical urban trees with heterogeneous canopy structures and high biodiversity. We developed two large-scale LiDAR morphological features in this research by, 1) modifying the rotate image method based on the axisymmetric structure to make it easier to use, and 2) developing an innovative adaptive ellipsoid method to extract the canopy features of the non-axisymmetric structure effectively. We evaluated the ability of these two morphological features to describe 12 common subtropical urban tree (SUT) species in Hong Kong growing in urban parks and streets, obtaining an accuracy of 88%. Our results illustrated that the rotate image feature based on the axisymmetric structure did not perform as well as the adaptive ellipsoid feature based on the non-axisymmetric structure in SUT, and the combined application of these two new morphological features got further accuracy improvement. The proposed method demonstrated significant advantages regarding the accuracy, the number of species, and the generalization capability compared to traditional methods on the identification of subtropical urban trees.

To date, studies on climate change and crop production have primarily focused on crop yield, whereas how cropping frequency (CF) responds to climate change remains poorly understood, especially at global scale. This is a critical knowledge gap because the addition or loss of a full cropping season has great implications for food security. This paper revised our understanding of the relationship between climate warming and CF. Although increasing CF is normally considered as an adaptation strategy to climate change, this study instead reveals a robust negative association between warming and global mean CF, suggesting that the adaptive potential of CF in response to global warming has been overestimated in all of previous studies.