Featured Published Research
PNAS
Prosocial nudges and visual indicators increase social distancing, but authoritative nudges do not
Social distancing reduces the transmission of COVID-19 and other airborne diseases. To test different ways to increase social distancing, we conducted a field experiment at a major US airport using a system that presented color-coded visual indicators on crowdedness. We complemented those visual indicators with nudges commonly used to increase COVID-19–preventive behaviors. Analyzing data from 57,146 travelers, we find that visual indicators and nudges significantly affected social distancing. Introducing visual indicators increased the share of travelers practicing social distancing, and this positive effect was enhanced by introducing nudges focused on personal benefits (“protect yourself”) and public benefits (“protect others”). Conversely, an authoritative nudge referencing the Centers for Disease Control and Prevention (“don’t break CDC COVID-19 guidelines”) did not change social distancing behavior. Our results demonstrate that visual indicators and informed nudges can boost social distancing and potentially curb the spread of contagious diseases.
​
JAMS
How lack of knowledge and psychological biases deter effective climate change action
In this research, we document knowledge gaps between consumers and experts about what consumer actions most effectivelyhelp mitigate climate change. We then identify three sources for lack of consumer knowledge on greenhouse gas emissionsassociated with consumption: carbon emissions labeling, awareness of indirect versus direct emissions, and orders of magnitude differences in carbon intensity across behaviors. We further propose that this lack of knowledge and several cognitiveand motivational biases lead consumers away from effective climate actions, including the tendency to focus on first- versus second-order effects of “green” behaviors, motivated reasoning that easier, more accessible actions are more impactful, and a focus on individual behavior versus systemic changes. We close with a research agenda designed to address the lack ofknowledge and biases we identify, while acknowledging that shifting marketers and consumers to focus on systemic changesmay be both most challenging and most impactful.
Resources, Conservation & Recycling
The convenience economy: Product flows and GHG emissions of returned
apparel in the EU
Each year, consumers return billions of new products to retailers. Despite growing concern over product destruction, post-return product flows are not well understood, and the full lifecycle environmental impacts of returns remain largely unknown. Building on a unique dataset covering over 630k returned apparel items in the EU, we map the flow of returned products under sustainable and conventional management practices, and quantify the full lifecycle impacts associated with returns using two illustrative apparel case studies. We find that 22%-44% of returned products never reach another consumer. Moreover, the GHG emissions associated with the
production and distribution of unused returns can be 2–16 times higher than all post-return transport, packaging, and processing emissions combined. Our findings suggest that the environmental impacts eCommerce and specifically online apparel, may be systematically underestimated when returns are not accounted for, and highlight the urgent need to promote circular management practices that maximize use of returned products.
Environmental Research Letters
The sharing economy is not always greener: a review
and consolidation of empirical evidence
The digital sharing economy is commonly seen as a promising circular consumption model that could potentially deliver environmental benefits through more efficient use of existing product stocks. Yet whether sharing is indeed more environmentally benign than prevalent consumption models and what features shape platforms’ sustainability remains unclear. To address this knowledge gap, we conduct a systematic literature review of empirical peer reviewed and conference proceeding publications. We screen over 2200 papers and compile a dataset of 155
empirical papers, and consolidate reported results on the environmental impacts of the sharing economy. We find that sharing is not inherently better from an environmental perspective. The type of resource shared, logistic operations, and the ways in which sharing influences users’ consumption more broadly affect environmental outcomes. Sharing goods is generally associated
with better environmental outcomes compared to shared accommodations or mobility. Within mobility, shared scooters and ride-hailing emerge as particularly prone to negative environmental outcomes. Contrary to previous suggestions, peer-to-peer sharing (vs. centralized ownership) does
not seem to be a good proxy for environmental performance. As sharing becomes intertwined with urbanization, efforts to steer digital sharing towards environmental sustainability should consider
system levels effects and take into account platform operations as well as potential changes in consumer behavior.
​
WIREs Climate Change
Policy for material efficiency in homes and cars: Enabling
new climate change mitigation strategies
Material efficiency (ME), making products with less material or substituting with less carbon-intensive material without a loss of functionality, can reduce greenhouse gas (GHG) emissions and complement other strategies to mitigate climate change. Seven ME strategies for cars and homes in the G7 countries were recently modeled in a study by the International Resource Panel. Modeling indicates that ME strategies focusing on construction and use of homes could lower the overall cumulative emissions in the G7 between 2016 and 2060 by 8.5 Gt CO2e (20%), while ME strategies for the production and use of cars could reduce up to 12 Gt (24%). For both homes and cars, the strategy of more intensive use—where fewer or smaller products are required to provide the same basic service—showed the greatest potential. A review of existing ME policies reveals that attention to ME in climate policy has been limited. Policy toward ME has historically focused on waste management rather than GHG reduction. Ex post evaluation of policies that do exist, especially for recycling and related waste strategies, is infrequent. Framing efficient use of materials as a measure primarily intended for climate mitigation is relatively recent and uncommon. Production-related policy opportunities have been neglected because using ME to reduce GHGs is novel in some sectors and because increased ME faces economic and social barriers. Rebound effects where reduction of the cost of housing or transportation can increase material consumption offsetting potential gains, a problem for all efficiency-based approaches, is understudied and not currently addressed through policy.
Nature Climate Change
Planetary impact shifts from fossil fuels to material extraction
As societies abandon fossil fuels in favor of renewable energy, electric cars and other low-carbon technologies, environmental pressures shift from atmospheric carbon loading to adverse impacts of material extraction and waste flows, new infrastructure development, land use change, and the provision of new types of goods and services. We call for interdisciplinary modeling to investigate this major change in environmental and social burdens and identify systemic demand-led mitigation strategies that explicitly consider planetary boundaries associated with the earth’s material resources.
Resources, Conservation & Recycling
Digital food sharing and food insecurity in the COVID-19 era
Sharing food surplus via the digital sharing economy is often discussed as a promising strategy to reduce food waste and mitigate food insecurity at the same time. Yet if and how the global pandemic has affected digital food sharing are not yet well understood. Leveraging a comprehensive dataset covering over 1.8 million food exchanges facilitated by a popular peer-to-peer food sharing platform, we find that UK activity levels not only rose during the Covid-19 pandemic, but outperformed projections. A potential explanation for this growth might be the rise of food insecurity during the pandemic. Yet examining the sociodemographic characteristics of platform users, average user activity and food exchanges before and during the pandemic, we find no compelling evidence that the platform's pandemic-era growth results from large influx of food insecure users. Instead, we poist that the growth in digital food sharing relates to lifestyle changes potentially triggered by the pandemic.
​
Journal of Industrial Ecology
Rebound effect and sustainability science:
A review
​
Journal of Cleaner Production
Is Repairability Enough?
A dominant narrative surrounding smartphone lifespans suggests that their objective functional capabilities deteriorate rapidly and that if only devices were more repairable consumers would use them longer thereby reducing demand for new production and e-waste generation. Here we use a big-data approach to help unpack this narrative and examine two related yet distinct aspects: smartphone performance and obsolescence, and consumers interest in repair. Examining over 3.5 million iPhone benchmarking test scores, we reveal that the objective performance of devices remains very stable over time and does not rapidly deteriorate as common wisdom might suggest. In contrast, testing frequency varies substantially. This discrepancy suggests that factors other than objective performance meaningfully influence consumers’ perceptions of smartphone functionality and obsolescence. Relatedly, our analysis of 22 million visits to a website offering free repair manuals revels that interest in repair declines exponentially over time and that repairability does not necessarily prolong consumer’s interest in repair. Taken together, our findings indicate that non-technical aspects, such as mental depreciation and perceived obsolescence play a critical role in determining smartphone lifespans, and suggest that focus on the technical aspects of repairability as currently discussed by policy makers is unlikely to yield the desired extension in smartphone lifespan. We propose that sustainability advocates try to avoid narratives of planned obsolescence which might have counterproductive impacts on perceived obsolescence and consumer’s’ interest in repair, and instead highlight how well devices perform over time. More broadly, this work demonstrates the potential of using novel datasets to directly observe consumer behavior in natural settings, and improve our general understanding of issues such as planned obsolescence and repair.
​
Journal of Industrial Ecology
Sharing economy rebound: The case of peer-to-peer sharing of food waste
The digital sharing economy is commonly thought to promote sustainable consumption and improve material efficiency through better utilization of existing product stocks. However, the cost savings and convenience of using digital sharing platforms can ultimately stimulate additional demand for products and services. As a result, some or even all of the expected environmental benefits attributed to sharing could be offset, a phenomenon known as the rebound effect. Relying on a unique dataset covering over 750,000 food items shared in the United Kingdom through a free peer-to-peer food-sharing platform, we use econometric modeling, geo-spatial network analysis, and environmentally extended input–output analysis to quantify how much of the expected environmental benefits attributed to sharing are offset via rebound effects under seven re-spending scenarios. We find that rebound effects can offset 59–94% of expected greenhouse gas (GHG) emission reduction, 20–81% of expected water depletion benefits, and 23–90% of land use benefit as platform users re-spent the money saved from food sharing on other goods and services. Our results demonstrate that rebound effects could limit the potential to achieve meaningful reductions in environmental burdens through sharing, and highlight the importance of incorporating rebound effects in environmental assessments of the digital sharing economy.
​
Journal of Sustainable Marketing
Psychological Barriers to Sustainability:
Understanding Consumer Demand for Products with Redundant Functionalities
Despite the proliferation of multifunctional products, survey data suggests that instead of relying on one multifunctional product, consumers now rely on a community of multifunctional products, using them interchangeably to perform similar tasks. Such consumption patterns stand in stark contrast to consumers’ well-documented aversion towards waste. Why are consumers willing to dispose of multifunctional products that still have some working capabilities and/or pay for functional redundancies? We suggest that controlling for the absolute level of performance (e.g., the megapixels of the camera), consumers perceive the same functionality to be less valuable when it is performed by a multifunctional product (e.g., the camera on a smartphone) than by a single, dedicated product (an inexpensive digital camera). We investigate this phenomenon across a series of four experiments which are aimed at documenting the basic effect and elucidating the underlying psychology.
​
Resources, Conservation & Recycling
Sustainable optimization of global aquatic omega-3 supply chain could substantially narrow the nutrient gap
Omega-3 EPA and DHA fatty acids are vital for human health, but current human nutritional requirements are greater than supply. This nutrient gap is poised to increase as demand increases and the abundance of aquatic foods and the amount of omega-3 they contain may dwindle due to climate change and overfishing. Identifying and mitigating loss and inefficiencies across the global aquatic supply chain has great potential for narrowing this nutrient gap. Here, using an optimization model, we show that omega-3 supply to humans could potentially increase by as much as 50% (reaching 630 kt y−1) compared to present baseline by shifting feed inputs to produce species that have the highest omega-3 content per feed input (i.e. carp and crustaceans), diverting other production flows towards direct wild fish consumption, improving byproduct utilization, and reducing waste at the retail and consumer level. We then discuss the implications of our findings by prioritizing policies and identifying demand- and supply-side interventions to realize these ambitious changes. This work emphasizes the urgency needed in managing aquatic resources towards greater utilization of resources and highlights the extent to which even partial adaptation of the measures we propose can have on narrowing the present and future nutrient gap as novel alternative sources of omega-3 become available on a larger scale.
​