Doctoral Dissertation Research: Human and Climate Influences on Yew (Taxus baccata L.) Population Dynamics in County Cork, Ireland, from 4,000 B.C. to the Present

University Of Florida, Gainesville FL

Investigators

Abstract

A critical facet of research on global change has been paleoenvironmental studies aimed at discerning past forms of global climatic and environmental change, especially in time periods since the last continental glaciation. This doctoral dissertation research project will identify factors that influenced yew tree (Taxus baccata L.) populations in the Irish parish of Youghal over the last 6,000 years, when human activity increased in Ireland. The Celts revered the yew tree as 'noble' and considered it a symbol of life and death. The Normans used it as raw material for the longbow. All species in the genus contain taxol, which has cured ovarian cancer. Yew is the longest-lived tree species in Europe. Scotland's Fortinghall yew is reputed to be 3,000 years old. Palynological analyses in Ireland are extensive, but the yew's former distribution and abundance is largely unknown, because its pollen has only recently been recognized. These qualities make it a worthy subject for cultural and paleoecological research. Regrettably, the yew now is not commonly found in Ireland. Youghal (Eo-chaill in Celtic, meaning 'yew forest') has only a few living yews remaining. This study hypothesizes that yew once was abundant in Ireland, as archival mentions of yew forests are common and toponymic analysis has revealed 124 Irish locations named after the tree. Youghal is home to freshwater peatlands (excellent for microfossil analysis), macrofossils (a forest of yew stumps adequate for dendrochronological analysis), and a well-documented history. Paleoecological and historical methods will be applied to identify climatological (temperature and precipitation) and sociological (cultural, economic, and political) factors that caused population fluctuations, and an eventual rarity, of yews in Youghal. These data should help determine whether human interference has been a more significant factor than climate change in the depletion of the yew, with levels of decline directly related to the scale and needs of human enterprise. This paleoecological project will contribute to knowledge of Holocene species declines and multidecadal scale climate reconstructions. Early paleoecological investigators assumed vegetational assemblages were primarily controlled by climate change. It has been realized that human activity may tremendously influence these assemblages. Humans have introduced exotic flora and fauna to compete with indigenous forms and executed further change by exhausting resources via deforestation and overkill. Paul Martin's Blitzkrieg Model suggests that fauna can become extinct as a result of human interference within a few hundred years. This research should help determine whether yew populations were depleted over a similar timespan, thereby providing a test as to whether flora are subject to human-induced rapid extinction. Every case of species decline is unique. In this case it is not believed that the arrival of humans lead to the immediate decline of this species but the arrival of a new cultural group (the Normans) with a different resource perception. The research will also contribute to Holocene climate reconstruction. Concerns about global warming have necessitated Holocene climate research in order to use the data to model future climates. Palynological data will reveal increases/decreases of yew pollen thus indicating changes in climate or human activity. These changes will be cross referenced with global Holocene climate data, analyzed in terms of other arboreal pollen changes, and compared to archival data. Dendrochronological data retrieved from the macrofossils will reveal climate conditions via tree ring anomalies. It will also complement the microfossil data in terms of dating events seen in the pollen profile. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.