The fifth lecture of our Planetary Boundary series took place on November 9th and was dedicated to the topic Freshwater Use. The lecture was held by Jonas Bunsen, who is a scientist at the Chair of Sustainable Engineering at the Technical University of Berlin where he works on environmental impact assessment with a particular focus on water.
He previously worked in public policy consulting at the think tank “adelphi” and in Life Cycle Assessment consulting at “Greendelta”, both located in Berlin, as well as for short term assignments at the KWR Watercycle Research Institute in the Netherlands and a branch of the International Water Management Institute in India. Jonas Bunsen holds a MSc in Water Science and Management from the University of Utrecht in the Netherlands and a BSc from the University of Innsbruck in Austria.
Jonas Bunsen started his lecture by pointing out that fresh water on planet Earth is not as abundant as one might think and particularly not evenly distributed. He continued with a general introduction to the planetary boundary Freshwater Use. The defined control variable is blue water consumption (fresh ground and surface water), which was considered by the authors of the planetary boundary Freshwater Use to potentially affect regional climate patterns, biomass production and consequently carbon uptake. Therefore, these processes are potential corresponding response variables.
As Jonas Bunsen points out, the planetary boundary Freshwater Use has been criticized from early on for comparing a local resource with global thresholds. On a global scale, this boundary is declared as not yet exceeded, but locally there are regions where water is already extremely scarce and people are suffering from water shortages. Moreover, blue water is also just one type of water consumption (disregarding e.g. indirect water consumption through land-use change and corresponding changes in evapotranspiration or water pollution), which has also been criticized to be one of the shortcomings of the planetary boundary concept, as well as dynamic thresholds and local tipping points. He gave an example for the latter: The Aral Sea shrank to 10% of its size, which has been called the “largest man-made water related catastrophe”, and still consequences have largely materialized on a regional scale.
Jonas Bunsen went on to show how a planetary boundary Freshwater Use has been put into practice, giving two examples of assessment methods: Life Cycle Assessment (LCA) and Input-Output Analysis (IOA).
LCA aims at mapping all production steps and corresponding inputs and outputs flows of a product life cycle, in order to evaluate potential environmental impacts. For the LCA, all flows which enter (inputs) and leave (outputs) the product system are listed and then grouped per respective impact category (e.g. climate change, water consumption).
He explained the method IOA by a case study example regarding Germany’s (in)direct water consumption. The study’s aim was to determine national German water consumption and then allocate the national water consumption to watersheds worldwide and benchmark against local water consumption boundaries. Bunsen and his colleagues calculated that, for Germany, 86% of the whole yearly water consumption is consumed abroad, considering consumers supply chains. As Jonas Bunsen pointed out, it is a model with approximate numbers, but an effective tool to identify local hotspots, where measures would have most leverage power.
He closed his presentation with a recent proposal on the water planetary boundary, which argued that water fulfills various functions in the earth system. Based on those core functions, six subboundaries (e.g. frozen water or soil moisture) with different response variables were proposed. Apart from frozen water, all are assigned to different spatial scales. As Jonas Bunsen finally concluded, the scientific community has moved to sub-global (regional) thresholds for assessing the impact of water consumptions as it can be questioned, if a planetary boundary for water really makes sense.
