The Threshold 21 (T21) system dynamics model allows for the representation of the food system within the larger framework of the three sustainable development dimensions, and so take into account the the essential connections in this complex system when assessing it. The T21 model allows therefore for a holistic, dynamic and systemic analysis of the food system and is a useful tool in the policy planners toolbox. This is particularly relevant for the development of national roadmaps for the SDGs, for which all countries will have to set their own realistic targets within the given range of options, design policies and set in place a strong monitoring and review system using a multistakeholder approach. This is true for the urban food needs, as well as for all other sectors of the economy, society and environment, as they are connected, or not, with the urban-rural food system. The use of the T21 model will help the decision makers in their quest to seek synergies and avoid negative feedbacks in the complex food system, highlighting the areas where leverage can be applied to optimize the many outcomes that will be relevant for an urban-rural food system that is multifunctional and sustainable.
Hans R Herren, President Millennium Institute