This agreement relates to the fourth part of the expected output of the scientific report acidification, viz. "When can restore soil acidification are expected to nature?" In order to answer this question is on a European level use is made of a dynamic modeling of soil acidification. The recovery of acidification is then defined on the basis of a soil chemical criterion. Simulating the main processes involved over time allows to determine the effect of a particular deposition on soil acidity for a given time. There will be made for this purpose of the Very Simple Dynamic Model (VSD-model) This model simulates the composition of the soil and the soil water through the time, on the basis of data on the soil type, vegetation, the atmospheric deposition and the annual precipitation. A first version of the VSD model was used for some forests in Flanders, with the aim of a receptor to determine the deposition of so-called target load at which the soil in 2030 would be fully recovered from acidification. For MIRA-S, however, relevant to determine the evolution of soil acidification in the deposition pressure of each of the proposed MIRA scenarios. This is an interesting and necessary addition when interpreting the results of critical loads for acidity. The determination of soil acidification in Flanders is particularly desirable for forest ecosystems, because the impact of atmospheric deposition on other semi-natural ecosystems (various types of heath and species-rich grasslands), mainly relates to the eutrophying effects of deposition; the dynamic modeling of over-fertilization, however, is beyond the scope of this MIRA-S. With the latest version of the VSD model the degree of soil acidification for both MIRA-S scenario's simulated over time for a comprehensive and representative set of Flemish forests.