Date of Award
Doctor of Philosophy in Biological and Environmental Sciences
Jason J. Kolbe
Invasive species are one of the most pressing threats to the conservation of biodiversity, to human health, and the economy today. Agricultural production and invasive species are often entangled in a complex web of interactions that ultimately decrease agricultural yield and lead to billions of dollars in losses. With no indicators of slowing globalization, it is imperative that we monitor the movement of potential pest species, prevent new introductions, and mitigate the impacts of invasive species. Comprehensive monitoring of potential invasions is not always possible, however, since it is often after a species is established that wildlife management and agricultural authorities realize the newly introduced species is a potential problem. At these junctures, effective mitigation and impact management is considered a better investment of management funds and human power than eradication. This dissertation assesses the level of impact of a potential agricultural pest, the green iguana (Iguana iguana) in Puerto Rico (Chapters 1 and 3) and evaluates the effectiveness of mitigation measures (Chapter 2).
Chapter 1 focuses on exploring the impact of the invasive green iguana on farms throughout Puerto Rico. We use one-on-one semi-structured interviews with farmers to determine the types of impacts they face, the crop species impacted, the actions taken to mitigate those impacts, and the perceived outcomes. We found that the green iguana has negative direct and indirect impacts on crop production. These impacts occurred more often at the lower elevation farms, and led to economic losses, emotional stress and modified behavior in farmers. We found that 33 crop species were consumed by the invasive reptile. In only one instance was a mitigation measure considered to be a solution to crop loss associated with invasive green iguanas rather than merely an example of impact reduction. This research was accepted for publication in the journal Management of Biological Invasions.
Chapter 2 focuses on quantifying the economic impact of the green iguana by evaluating its effect on the cultivation and yield of cucumber (Cucumis sativus). We also test two management strategies – Neem-based pesticide and mesh fencing – compared to open field cultivation (control group) in Puerto Rico to evaluate their utility as mitigation measures. We established two experimental fields in Agricultural Experimental Stations (Juana Diaz and Gurabo) in Puerto Rico and monitored each site for herbivory by green iguanas using researcher observations and camera trap. We found no crop consumption in Gurabo, but did observe herbivory in Juana Diaz. In Juana Diaz Mesh fencing doubled cucumber yield compared to open field cultivation but spraying Neem had no effect on cucumber yield. We estimated that this difference in yield could cost farmers in 2019 close to $4,000 per acre. This chapter was submitted to the journal Biological Invasions.
Chapter 3 focuses on exploring the breath of the green iguana impacts on agricultural production using a written questionnaire. Here we focus on the needs that management agencies could fulfill as identified by the 47 farmers who answered the survey. We find that farmers rely on each other for information about management techniques to mitigate green iguana impacts. We recommend that green iguana management become subsidized by governmental agricultural agencies due to its potentially large economic impact. Farmer reported collective losses of $106,590 in the year 2020 with additional economic strain of $13,350 per year due to management efforts. No support from government or non-governmental agencies to reduce those losses was identified. The results of this chapter will be submitted to the journal Conservation and Society.
De Jesus Villanueva, Christina N., "THE IMPACTS OF THE INVASIVE GREEN IGUANA (IGUANA IGUANA) ON AGRICULTURAL PRODUCTION AND THE COMMUNITIES OF PUERTO RICO — AN INTERDISCIPLINARY ASSESSMENT" (2022). Open Access Dissertations. Paper 1386.
Available for download on Friday, May 17, 2024