[Seminar Blog] People and Plants: The Human Impact on Plant Phenology and Diversity

 By: Amanda Brucchieri and Helen Craig
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On any given day, Dr. Tanisha Williams might be found exploring the desert in search of bush tomatoes, analyzing historical herbarium samples, or nurturing a vibrant community of Black botanists. What underscores all her work is the elevation and exploration of the relationships between people and plants, especially in the context of human mediated climate change caused by anthropogenic greenhouse gases (IPCC, 2013). In her work, Dr. Williams investigated how this change is affecting the phenology and diversity of plants, particularly in the context of climate change and Traditional Ecological Knowledge (TEK).  

Figure 1. Pelargonium are a genus within the family Geraniaceae. The genus, Pelargonium, has many different species, a few of which are illustrated here. (Photo: Matija Strlic)

To explore possible links between climate change and plant phenology and diversity, Dr. Williams worked with herbarium specimens collected in the Cape Floristic Region of South Africa, an area known for its diverse plant community and the third most biodiverse country in the world (Wynberg, 2002). She focused on the Cape Floristic Region - an area with a very diverse plant community. This region is experiencing the world’s second greatest rate of plant extinctions, having lost 37 species since 1990 (Humphreys et al., 2019). Dr. Williams conducted her research on the genus Pelargonium (Figure 1). Pelargoniums are an amazingly useful genus of plants known for their use in landscaping, medicinal, and commercial products (the artificial rose scent is derived from this family). Pelargonium species are also well represented in South African herbarium collections. By recording the calendar date flowering plant specimens were collected, Dr. Williams was able to document that between 1850 and 2010, Pelargonium plants were flowering an average of 7 days earlier. Over this period the region also experienced an increase in annual temperature of about 2.9 ℃, suggesting a possible relationship between temperature and flowering time .Dr. Williams suggests that the change in Pelargonium species' flowering date, warns of changing ecological relationships, which could lead to ecosystem collapse if too many of these relationships are lost or changed. 

Climate change is not the only anthropogenic activity that affects plant evolution and the ecosystems that are dependent on them, there are some counter-acting agents. Indigenous and Aboriginal cultures use TEK which also plays a role in plant evolution. Dr. Williams and her colleagues at Bucknell University demonstrated this when working with the Martu people in western Australia. The Martu people have a very close connection to the Wamula plant (Solanum diversiflorum), also known as the “bush tomato”. Dr. Williams and a team of scientists studied populations of Wamula within and outside of the Martu title lands located in the Western Australian deserts. They demonstrated that the Martu people were connecting populations of these plants within their territories, fostering genetic diversity through anthropogenic dispersal, while Wamula plants outside of the Martu lands showed no connection between plant populations. More on how Dr. Williams and her colleagues uncovered this relationship is documented in a YouTube channel entitled “Plants are Cool Too” (Image 1). 

Image 1. Screenshot of youtube video titled “How One Aboriginal Community is Making Things Better for an Important Plant | Plants are Cool, Too!” highlighting Dr. Williams' work with the Martu people in Australia and their cultivation of Wamula, a wild bush tomato.

Figure 2. Place-based land care practices by Dr. Cristina Eisenberg, depicting how local knowledge and western science can work together to create more effective solutions to global and local ecological problems.

Dr. Williams encouraged us, not only as scientists but as human beings, to understand the value of Traditional Ecological Knowledge. Connecting TEK with western scientific practices is our way of “seeing with both eyes”. Dr. Williams demonstrates this eyes-open ideal through her work with the Gullah Geechee people, where they are developing a plant guide for the region using both the assigned scientific names and Gullah Geechee names.  This plant guide acts as a communication tool, developing a bridge between knowledge of Indigenous cultures and modern science. By doing so, Dr. Williams is creating opportunities for modern techniques to be applied using traditional knowledge that more effectively conserves plants at risk of extinction. Co-creating projects, such as the Gullah Geechee plant guide using TEK is an excellent way of “two-eyed seeing” the relationship between plants and humans (Figure 2). 
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Through her work with herbaria, the Martu people, and the Gullah Geechee people, Dr. Williams explores the complex relationship between people and plants. She demonstrates how important it is to learn how anthropogenic climate change can alter a plant’s phenology and how Traditional Ecological Knowledge can aid in understanding and conserving plant biodiversity. Dr. Williams emphasizes the importance of advocacy and partnership in her work. It takes many diverse minds to understand the complex relationships between plants and people. Putting time and effort into relationships will foster trust and develop support systems that can become immeasurably fruitful, prompting action. In the words of Dr. Williams “Show up”. Show up for yourself, for your community, and for the causes you believe, in whatever way you can.  

P.S. She is hiring! You can find her lab and information about applying on the University of Georgia website, on the  Williams’ Lab website, and on the UGA herbarium instagram page.  
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References: 
Antonelli, A., et al. (2020). State of the World’s Plants and Fungi (Doctoral dissertation, Royal 
Botanic Gardens (Kew); Sfumato Foundation). https://www.kew.org/sites/default/files/2023-10/State%20of%20the%20World%27s%20Plants%20and%20Fungi%202023.pdf 

Hartley, A. J., & Tandon, A. (2022) The impacts of climate change. Frontiers.
https://kids.frontiersin.org/articles/10.3389/frym.2022.716479 

Humphreys, A. M., Govaerts, R., Ficinski, S. Z., Nic Lughadha, E., & Vorontsova, M. S. (2019). 
Global dataset shows geography and life form predict modern plant extinction and rediscovery. Nature ecology & evolution, 3(7), 1043-1047. https://www.nature.com/articles/s41559-019-0906-2 

IPCC (2013). Climate change 2013: The physical science basis. Working Group I contribution to 
the fifth assessment report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex & P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, p. 869. https://www.ipcc.ch/report/ar5/wg1/ 
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Randall, B. (2020). The value of birds and bees. USDA Farmers.gov. 
https://www.farmers.gov/blog/value-birds-and-bees 

Losey, J. E., & Vaughan, M. (2006). The economic value of ecological services provided by 
insects. Bioscience, 56(4), 311-323. https://academic.oup.com/bioscience/article/56/4/311/229003 

Wagner, D. L. (2020). Insect declines in the Anthropocene. Annual review of entomology, 65, 
457-480. https://www.annualreviews.org/content/journals/10.1146/annurev-ento-011019-025151 

Wynberg, R. (2002). A decade of biodiversity conservation and use in South Africa: tracking 
progress from the Rio Earth Summit to the Johannesburg World Summit on Sustainable Development. South African Journal of Science, 98(5), 233-243. https://www.researchgate.net/publication/279655302_A_decade_of_biodiversity_conservation_and_use_in_South_Africa_Tracking_progress_from_the_Rio_Earth_Summit_to_the_Johannesburg_World_Summit_on_Sustainable_Development 

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