Modelling the Water-Energy-Food-Land-Climate Nexus: The Nexus Tree Approach

The European Horizon 2020 project SIM4NEXUS explores the network of interlinkages between Water, Land, Food, Energy and Climate. A direct interlinkage between two nexus components, for example Water and Energy, was defined as the change in a component’s status (Energy) caused by a change in another component’s status (Water), assuming that the other nexus components (Land, Food and Climate) remain constant and do not interfere with the status of the two components.

This was referred to as the Water‐Energy direct interlinkage, denoted as ‘WE’. Each direct interlinkage is unilateral, consequently ‘WE’ differs from ‘EW’. According to this framework, the unique direct interlinkages of the Nexus dimensions sum up to 20. These direct interlinkages were considered as first order interlinkages. However, one Nexus component may also affect another through indirect interlinkages. Therefore, second, third and fourth order linkages were distinguished.

A ‘Nexus tree’ is the schematic depiction of all different pathways that lead to first and higher order effects on nexus domains, caused by a change in one of the nexus components. As only the one‐to‐one relationships of Nexus components are described, and the Nexus tree does not consider feedback loops, this is just a first step to describe a far more complex reality that goes beyond imagination.

To deal with feedback and multilateral relationships, SIM4NEXUS uses System Dynamics Modelling that combines the bilateral links of the Nexus tree into networks and complex systems.