Public defence in Water and Environmental Engineering, M.Sc. (Tech) Vili Virkki

Title of the thesis: Freshwater change in the Earth system: A qualitative-quantitative outlook and implications for planetary boundaries.

Doctoral Student: Vili Virkki
Opponent: Researcher Hester Biemans, Wageningen University & Research, The Netherlands
Custos: Professor Matti Kummu, Aalto University, School of Engineering, Department of Built Environment

Human-driven water cycle modifications and their importance in the Earth system – how human activities change the freshwater cycle.

Human-induced changes in various biophysical processes in the Earth system are remarkable – exemplified not least by climate change, biodiversity loss, the spread of land use to nearly every corner of the globe, and the harnessing of the water cycle for human needs. This globally pervasive environmental change comes with elevated risks; to understand these risks, the “planetary boundaries” framework has emerged as highly influential in recent years. However, despite the widespread popularity of the framework, the definition of the planetary boundary for freshwater has been seen as relatively limited. 

The dissertation deals with human-driven changes in the global freshwater cycle. The research qualitatively explores interconnections between different Earth system processes – such as the water cycle, land cover, and ecosystems – as well as the associations between river flow changes and related drivers – such as water use and damming. Quantitative analyses, in turn, illustrate in detail how much, where, and when the freshwater cycle has changed following industrialisation. These findings contribute to defining a new planetary boundary for freshwater, which is also presented in the dissertation. 

The dissertation shows how human activities have pushed the freshwater cycle far beyond the stable state that prevailed before the industrial revolution. The redefined planetary boundary for freshwater, which better captures the importance of freshwater in the Earth system, is seen notably transgressed shortly after industrialisation. This conclusion contrasts previous planetary boundary estimates for freshwater but is well in line with many other studies describing longstanding changes in the water cycle. 

The clear transgression of the planetary boundary is a warning signal of the serious risks associated with changes in the freshwater cycle. The results of the dissertation aid in safeguarding the freshwater cycle as an integral part of the Earth system. This is of utmost importance because human activities have become to dominate this vital process, and, in addition to changes in water resources, significant adverse impacts are occurring in other Earth system processes that are tightly interlinked with the freshwater cycle. The global research presented here also provides a strong basis for further studies delving even deeper into the causes and consequences of change in the freshwater cycle.

Keywords: freshwater cycle, planetary boundaries, hydrology, global environmental change

Thesis available for public display 10 days prior to the defence at: https://aaltodoc.aalto.fi/doc_public/eonly/riiputus/

Contact information of doctoral student: Vili Virkki, [email protected] 

Doctoral theses of the School of Engineering: https://aaltodoc.aalto.fi/collections/8e3155b2-5002-4961-b951-bf10d41ce241
 

Zoom Quick Guide: https://www.aalto.fi/en/services/zoom-quick-guide