Dr. Lucy Hutyra

Dr. Lucy Hutyra, Associate Professor of Earth and Environment, Boston University; Director, Hutyra Research Lab, Boston University, Boston, MA

Research interests: Using Earth observing data to improve our understanding of the carbon cycle, particularly how changes in vegetation and land use impact flows of carbon between the biosphere and the atmosphere.

Research highlights: Since colonial days, Boston, MA, has remained one of the largest U.S. cities, and the population of this metropolis is poised to surpass 700,000 residents, according to the U.S. Census (the city last hit this milestone in the 1920s). One consequence of this large population, though, is the production of high carbon emissions.

According to 2015 figures from the Massachusetts Department of Transportation, the entire Boston Central Artery/Tunnel project processes more than 530,000 vehicles per weekday and the Massachusetts Bay Transportation Authority (MBTA) that services the Boston region logs nearly 1.3 million daily trips on its subway, bus, and commuter rail system. While not all of these vehicles use fossil fuel-burning internal combustion engines, those that do create about 8.8 kilograms of carbon dioxide (CO₂) for every gallon of gasoline burned, according to the U.S. Environmental Protection Agency, and the average passenger vehicle equipped with an internal combustion engine emits roughly 4.6 metric tons of CO₂ per year. All this carbon adds up, especially in urban areas like Boston. And these urban areas are expected to grow dramatically over the next decade.

In fact, by 2030 “urban areas are projected to house 60% of people globally and one in every three people will live in cities with at least half a million inhabitants,” according to a United Nations report. As Dr. Lucy Hutyra observes, the anticipated growth in urban areas over the next decade is “more urban land expansion than in all of history.”

Hutyra’s research focuses on developing a better understanding of how fossil fuel emissions of CO₂ coupled with biological activity in urban environments influences atmospheric CO₂ concentrations. Much of her work is conducted out of the Hutyra Research Lab at Boston University and spans urban-to-rural gradients. NASA remotely-sensed atmospheric data enable her to scale her ground-level carbon investigations across much larger regions. This is critical, given the impact carbon has on life on Earth.

Carbon is the fourth most abundant element in the universe by mass, and exists in gaseous forms that include carbon dioxide (CO₂), methane (CH₄), and carbon monoxide (CO). Carbon constantly cycles in and out of the atmosphere, with CO₂ being the most abundant atmospheric carbon-bearing gas. In the absence of external inputs, the carbon cycle stays in balance, with natural CO₂ inputs from sources such as animals and forest fires roughly equaling natural sinks that take CO₂ out of the atmosphere, like oceans and the process of photosynthesis.

Human activities, including urban growth, deforestation, and the burning of fossil fuels, have led to an increase in atmospheric CO₂ beyond what would be expected from natural sources. In 2017 alone, more than 41 billion tons of CO₂ were emitted to the atmosphere from anthropogenic sources including land use change and the burning of coal, oil, and gas, according to the 2018 Global Carbon Budget report created by the international Global Carbon Project. This excess atmospheric CO₂ helps trap radiated heat, much as the glass of a greenhouse prevents the escape of solar radiation. Thanks to instruments aboard Earth observing satellites, atmospheric CO₂ can be measured and tracked 24/7.

One orbiting data source used by Hutyra is NASA’s Orbiting Carbon Observatory-2 (OCO-2). Launched in 2014, OCO-2 is a re-flight of the original OCO mission, which failed on launch. OCO-2’s primary science objective is to collect measurements of atmospheric CO₂ with the precision, resolution, and coverage needed to characterize its sources and sinks and to quantify the variability of CO₂ over seasonal cycles. OCO-2 provides roughly 100,000 global CO₂ measurements every day. Originally intended for a three-year mission, OCO-2 is still sending back valuable data.

OCO-2 data soon will be complemented with data from OCO-3, which successfully launched on May 4, 2019, and was installed on the International Space Station (ISS) on May 6. OCO-3’s location on the ISS provides a number of advantages, such as the ISS’ lower orbital altitude. While OCO-2 circles Earth in a 705-km polar orbit, the ISS orbits Earth between 52° north and south latitude at an altitude ranging from 330 to 435 km. This lower orbit enables OCO-3 to collect denser data than OCO-2 over high-carbon regions, such as the Amazon. More importantly, OCO-3 will pass over major cities and urban areas at different times of day, enabling it to collect data spanning all sunlit hours and provide a more precise picture of urban CO₂ changes throughout the day.

As Hutyra notes, individual cities have taken the lead in U.S. efforts to reduce greenhouse gas emissions. In a recent paper looking at a model for assessing CO₂ concentrations in Boston, Hutyra and her colleagues observe that a detailed representation of urban biological fluxes combined with a knowledge of the spatial and temporal distribution of emissions is essential for accurate modeling of annual CO₂ emissions. These data, covering all daylight hours over urban areas, soon will be available through OCO-3.

Another remotely-sensed variable used by Hutyra in her research is a nearly invisible fluorescent glow created by chlorophyll in plants that can be detected by sensors like those aboard the OCO satellites. This “vegetative fluorescence” provides valuable information about the productivity of terrestrial vegetation and enables scientists to estimate the rates of photosynthesis across large areas. If fluorescence decreases, this is an indication that plants are not as productive. Since plants play a key role in removing CO₂ from the atmosphere, less productive plants mean less CO₂ being removed. Conversely, as plants die and decay, they release CO₂ back into the atmosphere and become a carbon source rather than a carbon sink. In addition, fluorescence data help resolve some uncertainties about the uptake of CO₂ by plants in climate models.

One final NASA asset used by Hutyra and her colleagues is NASA’s Carbon Monitoring System (CMS). Since its establishment in 2010, the CMS has served as a collaborative platform for incorporating remotely-sensed carbon data and measurements into a wide range of products and datasets designed “to support stakeholder needs for Monitoring, Reporting, and Verification (MRV) of carbon stocks and fluxes.” Hutyra has participated as a co-investigator on several CMS projects and is a member of numerous CMS Groups. As noted in a recent article on CMS, Hutyra was part of a team that used a CMS grant to develop methods “for detecting and attributing methane leaks from urban natural gas pipelines,” which contributed to changes in how Boston and the state of Massachusetts regulate gas leak repairs.

As urban areas continue to expand in area and population, the need to understand the carbon contributions of these metropolises becomes ever more important. Through remotely-sensed data and ground observations, Dr. Lucy Hutyra and her colleagues are developing a better understanding of the effects of urban carbon emissions and their impacts—not just for Boston, but for urban areas around the world.

Representative data products used:

• NASA’s Carbon Monitoring System (CMS): CO₂ Emissions from Fossil Fuels Combustion, Anthropogenic Carbon Emissions System (ACES) Inventory for Northeastern USA (doi:10.3334/ORNLDAAC/1501); available through NASA’s Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC)
• MODIS Collection 6 Land Product Subsets Web Service (doi:10.3334/ORNLDAAC/1557); available through the ORNL DAAC
• OCO-2 Level 2 bias-corrected solar-induced fluorescence and other select fields from the IMAP-DOAS algorithm aggregated as daily files, Retrospective processing V8r (Shortname: OCO2_L2_Lite_SIF (doi:10.5067/AJMZO5O3TGUR); available through NASA’s Goddard Earth Sciences Data and Information Services Center (GES DISC)

Read about the research:

Popkin, G. (2019). New Budget Bill Rescues NASA’s Carbon Monitoring System. EOS, 100; published on 28 February 2019. doi:10.1029/2019EO117385

Sargent, M., Barrera, Y., Nehrkorn, T., Hutyra, L.R., Gately, C.K., Jones, T., McKain, K., Sweeney, C., Hegarty, J., Hardiman, B., Wang, J.A. & Wofsy, S.C. (2018). Anthropogenic and biogenic CO₂ fluxes in the Boston urban region. Proceedings of the National Academy of Sciences of the United States of America, 115: 7491-7496. doi:10.1073/pnas.1803715115

Smith, I.A., Hutyra, L.R., Reinmann, A.B., Marrs, J.K. & Thompson, J. (2018). Piecing together the fragments: Elucidating edge effects on forest carbon dynamics. Frontiers in Ecology and Environment, 16(4): 213-221. doi:10.1002/fee.1793

Hardiman, B., Wang, J., Hutyra, L.R., Gately, C., Getson, J. & Friedl, M. (2017). Accounting for urban biogenic fluxes in regional carbon budgets. Science of the Total Environment, 592: 366-372. doi:10.1016/j.scitotenv.2017.03.028

Trlica, A., Hutyra, L.R., Schaaf, C., Erb, A. & Wang, J. (2017). Albedo, Land Cover, and Daytime Surface Temperature Variation Across an Urbanized Landscape. Earth’s Future, 5: 1084-1101. doi:10.1002/2017EF000569

For more information

• Hutrya Research Laboratory
• Orbiting Carbon Observatory-2 (OCO-2)
• Orbiting Carbon Observatory-3 (OCO-3)
• Carbon Monitoring System

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