Many countries in the world are in ecological overshoot. That is the message that the Ecological Footprint calculated by the Global Footprint Network sends us. Since many developing countries may not be in overshoot yet, but are heading for it, it is very important that their development paths leapfrog to resilient sustainable development. The Ecological Footprint cannot give a good answer to the question of which policies could achieve this, because as an ecological accounting tool it is intrinsically of an ex-post nature. The Threshold 21 models have been developed by the Millennium Institute for the precise purpose of allowing for sustainable national development planning using System Dynamics, but they currently lack the Ecological Footprint. This thesis is a pilot project assessing to what degree it could be possible to implement a dynamic version of the forest Ecological Footprint (and the forest biocapacity) in the T21 model of Senegal. It was found that while it is possible, it requires a great deal of additional information that is hard to find in publicly available sources. Nevertheless, the project has already led to suggestions for improvements for the GFN methodology and the T21 model: switching from a constant to a variable annual forest increment is the most pressing issue, and the T21 model should be extended by a conversion flow from forest land to cropland. Overall, the implementation of the whole Ecological Footprint in T21 is highly recommendable, as both the T21 model and the Ecological Footprint methodology would benefit from it.