Monday, December 28, 2020
  Faculty Focus, Research

By Victoria Brito

RIO GRANDE VALLEY, TEXAS – Smoke clogs the air. The outcome is grim. 

This research is not for the faint of heart. 

Dr. Cheryl Harrison, assistant professor in the School of Earth Environmental, and Marine Sciences, is part of a research project that simulates the environmental and human impacts of a nuclear war.

Harrison, who specializes in biophysical modelling, is leading the ocean impacts studies for the broader research project, including impact on fisheries. She recently led a paper, titled “Marine wild-capture fisheries after nuclear war,” which has been published in Proceedings of the National Academy of Sciences of the United States of America, a high-impact scientific journal.

Harrison co-lead this paper with Kim Scherrer, a graduate student at Institut de Ciencia i Tecnologia Ambientals-Universitat Autinoma de Barcelona, along with other members of a lab led by Eric Gailbraith, professor in the Department of Earth and Planetary Science at McGill University in Montreal, Canada.

The study simulates global fisheries’ catch and biomass responses for a number of nuclear war scenarios, along with the possible socioeconomic responses in fishing, such as increased, decreased, and “business-as-usual” behaviors.


In this study, it is shown that fishing pressure has a greater impact on fish catch and biomass than larger climate issues, such as global cooling, that would result from a possible nuclear winter.

“Because fisheries worldwide are already so heavily fished, the reduction of fishing pressure that could occur due to possible interruption of infrastructure or decrease in population post-war, results in an increase in global fish biomass,” Harrison said.

Biomass is the renewable organic material that comes from plants and animals.

“This means we can manage fisheries to have higher biomass and thus maximize the potential they have to offset agricultural loss during global cooling events,” Harrison said. “These agriculture losses are generally larger because land is more affected by heating and cooling than the ocean.” 

Harrison said this work extends to global cooling events that would occur due to volcanic eruptions, or war, which also would influence fisheries.

Global cooling occurs when the smoke from a burning situation rises to the atmosphere, blocks sunlight and cools the planet. This can result in agricultural failures and changes in precipitation.

When cooling occurs, food supply is impacted from various angles.

“When you have a lot cooling and there is smoke in the atmosphere, it cools the planet and the rains fail,” Harrison said. “As a result, you can’t grow food. We only have a few months of food reserves globally. And so, you can imagine if all the crops fail, people would fight over those reserves.”

Harrison said that when cooling occurs, the lack of light also decreases phytoplankton (fish food) growth, which creates complications with fish supply.

“Right now, the oceans are overfished,” Harrison said. “We really have reached the capacity of how much fish we can get out of the ocean, and we currently have more boats with capabilities than fish available. That is why fishing seasons are in place.”

Harrison said publication of this study is just the first of more papers and research to follow.

“We see this as a first step in a series of papers that will combine the fisheries and agricultural impacts under a climate shock, allowing us to better study the whole food system under these extreme climate events,” Harrison said.


UTRGV students have had the opportunity to participate in hands-on research.

Jessica Stevens is a graduate student in the SEEMS department and is mentored by Harrison. When she joined this research project in 2019, Stevens was informed that computer coding would be necessary. Though she was not familiar with the skill, she quickly learned and was able to get impactful experience.

“This research was actually my introduction to coding,” Stevens said. “Dr. Harrison equipped me with the basics of it and enlisted me for this research. With my bachelor’s degree in biology, all of the science of the data behind the coding made a lot of sense when applied.”

Stevens would create plots to show the effects nuclear war would have on primary production and photosynthetic reactive radiation and temperature.

She hopes to pursue a doctorate degree and said coding has enhanced her research skillset.

“Being able to visualize and analyze data is key in research and learning. To think through these visuals and possibilities and variables, and then writing it up, has been very valuable for me,” she said.

Also making plots was Victoria Garza, a junior computer science major. The research gave her the opportunity to use her computer science knowledge and to be involved in research in a field other than her specialized field of study.

“I would make plots using data and I would put them into moving graphics to see the effects over time happening slowly and progressively,” Garza said.

August Luna, a junior math major, is a former coder for Harrison, who gained valuable experience using Python, the graphing software used by the team to display variables.

“I was involved in making graphs using Python, and I learned a lot,” Luna said. “I learned how to code on the program, use it to make graphs and work with arrays. I learned to read documentation and problem solve.”


The University of Texas Rio Grande Valley (UTRGV) was created by the Texas Legislature in 2013 as the first major public university of the 21st century in Texas. This transformative initiative provided the opportunity to expand educational opportunities in the Rio Grande Valley, including a new School of Medicine, and made it possible for residents of the region to benefit from the Permanent University Fund – a public endowment contributing support to the University of Texas System and other institutions.

UTRGV has campuses and off-campus research and teaching sites throughout the Rio Grande Valley including in Boca Chica Beach, Brownsville (formerly The University of Texas at Brownsville campus), Edinburg (formerly The University of Texas-Pan American campus), Harlingen, McAllen, Port Isabel, Rio Grande City, and South Padre Island. UTRGV, a comprehensive academic institution, enrolled its first class in the fall of 2015, and the School of Medicine welcomed its first class in the summer of 2016.