Max Carroll, an undergraduate junior at the Krieger School of Arts and Sciences from Cleveland, Ohio, has been involved with sustainability on campus throughout his time at JHU. He is an Environmental Science and Behavioral Biology double-major, the president of the environmental science honors society Sigma Gamma Epsilon, and he helps manage the campus pop-up thrift shop program with Sustainable Hopkins Innovative Projects (SHIP).
Max has been a member of Dr. Meghan Avolio’s lab since the spring semester of his freshman year. The Avolio Lab studies grassland and urban ecosystems, and “aims to understand the mechanisms by which humans directly and indirectly alter plant populations and communities and whether there are consequences for ecosystem function,” according to the lab’s website.
This summer, Max assisted graduate student Eric Yee on a research project that examined how different weed species adapt to the urban climates of different cities. The project took place in the greenhouse on the Homewood campus, as well as in the Avolio Lab in Olin Hall.
We sat down with Max to learn more about the research:
Describe the intention of the research as it relates to environmentalism and the climate.
“There are many things that change when you go from a rural to urban area, including the amount of impermeable surfaces, of heavy metals in the soil from industrial activity, and the presence of the urban heat island effect,” says Max.
Such changes in environmental conditions influence flora, whether it be through changes in physical characteristics, life history strategies, or other avenues.
“There is a lot of research along the rural-urban gradient, seeing how plants evolve,” says Max. “But there isn’t as much study on how plants are adapting to different cities.”
Individual cities present varying conditions, so the same plant species may grow differently from one city to the next. Climate change further amplifies these differences in species growth across cities due to increased temperature, precipitation, and other environmental impacts.
The question at the heart of this research is whether such changes result from adaptation.
Though selective pressures have changed, the force of natural selection is present in modern day cities just as it is in the wild; just as it has been throughout the history of life.”
To study this, the lab grew seeds of dandelions (Taraxacum officinale) and prickly lettuce (Lactuca serriola) from Baltimore, Maryland and Minneapolis-Saint Paul (MSP), Minnesota. Baltimore is generally a hotter, more humid city, while MSP is cooler, cloudier, and windier. Such differences would be used as means for comparison of species growth.
The seeds were grandchildren bred from a grandparent generation — a process conducted to breed out any phenotypic plasticity due to the environment, or the ability of genotypes to produce different phenotypes in different environmental conditions, that might occur in such species. In doing so, any differences in the characteristics of the grandchild generation could be attributed to genetic change and adaptation.
“We wanted to see if changes in the weeds from each of the cities were the result of phenotypic plasticity, or if they were actually adapting to the hotter versus the cooler city,” says Max.
After seeds were germinated in a climate controlled growth chamber, Max helped plant the seeds in the campus greenhouse. Pots were randomized so that different plants from different cities were mixed across trays — each receiving an even amount of light. Throughout the summer, Max watered and cared for the plants, taking periodic measurements and monitoring their growth. Come October, Max and Eric harvested the plants to measure their above and below ground biomass, along with other characteristics.
“What we found was that prickly lettuce grew taller, bolted earlier, and had more biomass in MSP,” says Max. “The dandelions from Baltimore had more aboveground biomass than MSP. We don’t really know why yet, but the results were significant, so these were actual adaptations.”
“A main takeaway from this research is that plants are adapting to different cities similarly to how they would without the presence of humans,” says Max. “Though selective pressures have changed, the force of natural selection is present in modern day cities just as it is in the wild; just as it has been throughout the history of life.”
What are the greater implications of this research? How could the findings contribute to a more sustainable future?
“Plants are important and provide many benefits to the environment and to human health, such as reducing heat and increasing mental health,” says Max. “By understanding how plants behave in cities, we can keep cities plant-friendly to ensure that we keep those benefits.”
Through this research, Max says, “We are better at understanding how weeds adapt, which gives us insight into how other plants might adapt to changing urban climates.”
Cities are ecosystems, and we need to understand them to make sure they stay stable.”
Next summer, he plans to conduct the same experiment with another closely-related weed species (Erigeron canadensis; common horseweed), to see if any patterns can be observed.
“A lot of people see cities as being separate from the natural world, and I think what this research shows is that humans aren’t separate from the natural world,” says Max. “Cities are ecosystems, and we need to understand them to make sure they stay stable.”
What is the importance of environmentally-focused research?
“In some ways it is like preventative medicine,” says Max. “We are going to have to fix the damages in our environment eventually, whether we like it or not. By understanding the environment now and trying to create a better, more sustainable society, we are preventing loss of life and loss of quality of life.”