Most of humanity's basic needs are related to the commodities water, food and energy. Driven by economic development and population growth, the use of water, food and energy has continued to increase rapidly during the past 40 years. However, the increasing extraction of natural resources has damaged the natural environment at unprecedented speed and scale, thereby also threatening the fulfilment of future needs. This problem has spurred a worldwide quest for sustainability, to meet both present and future needs, for example in the form of the global Sustainable Development Goals.
In this thesis, we contribute to model-based scenario analyses, exploring possible paths to different futures, based on independently progressing trends and various policy options. We add to an existing body of process-based integrated assessment models, with particular attention for long-term consequences, for inequality among population groups, and for the interconnectedness of water, food and energy. The topic is approached from the demand side and builds on the IMAGE model framework, leading to the following research questions:
• How may water and food demand develop in the long-term future?
• How are the demand and supply of water, food and energy interrelated?
• What does increasing water demand mean for water scarcity?
• How do water and food factor into local and global inequalities?
Key findings include:
Water demand is projected to increase significantly in the future in most scenarios, especially for non-agricultural uses. Efficiency improvements are a key factor in limiting the rapid growth of water demand. These include end-use water efficiencies, but also the thermal efficiency (fuel-to-electricity conversion) of power plants.
Although future food demand per capita differs between socio-economic scenarios, the total food demand is still projected to increase significantly in all scenarios. Wide-spread adoption of a low meat diet or of artificially grown meat can effectively temper the growing demand for crops and grass. Food waste reduction and animal feed efficiency have less potential impact on total demand.
Water, food and energy flows are very different in terms of absolute magnitude and the extent to which they are transported. The global and continental scales are important for nexus problems, since physical and virtual trade can provide solutions beyond the local or national scales.
Improved models are needed to capture the complex interactions between water demand, availability and scarcity across spatial scales (local, river basin, regional, and global). Different priority rules at the local level have a large impact on non-agricultural water deficits, whereas the watershed-level option of limiting irrigation expansion has less effect.
Inequality of food consumption between population segments in the same region is of the same magnitude as differences between regions. Even in 2050, projected consumption for some population segments is still very low in terms of total calories, protein grams, and/or fruit and vegetable consumption. If the increasing food demand in middle-of-the-road scenario SSP-2 can actually be met by increased production, the estimated global number of undernourished people is projected to decrease from 700 million in 2015 to 270 million in 2050 and almost zero in 2100.