Dissertation defence (Economic Geography): MSc Oliver Tomassi

MSc Oliver Tomassi defends the dissertation in Economic Geography titled “Transitioning towards sustainable development in Tanzania: The case of mercury and cyanide in artisanal and small-scale gold mining” at the University of Turku on 3 June 2026 at 12.00 (University of Turku, Natura, Lecture Hall XV, Turku).

Opponent: Professor Roy Maconachie (University of Bath, UK)

Custos: Professor Jussi Jauhiainen (University of Turku)

Summary of the Doctoral Dissertation:

Artisanal and small-scale gold mining (ASGM) is an economic activity that uses simple tools and low-cost methods to extract gold. It is labour-intensive and widely practiced in rural areas. ASGM plays a vital role in supporting livelihoods in the Global South, where formal employment opportunities are often limited. In Tanzania, the focus of this study, over one million people work in the sector, with many more depending on it indirectly.

Mercury is a key technology in ASGM. It enables miners to extract gold cheaply and with little technical training. However, mercury is highly toxic and poses serious risks to both human health and the environment.

In recent years, an alternative technology to extract gold has emerged: cyanide leaching. While this may appear to be a cleaner solution, it is more expensive and requires specialized knowledge and equipment to extract gold safely and effectively.

This dissertation explores how the introduction of this technology has changed gold mining in Tanzania. The findings show that mercury use persists not only because it is affordable and easy to use, but also because it is deeply embedded in everyday practices and livelihoods. Meanwhile, although cyanide is more efficient at extracting gold, its higher costs risk increasing inequality by excluding many small-scale miners who cannot afford it. In practice, it is also common for miners to use both mercury and cyanide in the same process, which further increases environmental harm.

Overall, the study questions whether replacing mercury with cyanide can truly be considered a move toward sustainable development. It highlights the need for policies that support a more inclusive transition—one that protects both livelihoods and the environment.