The value of investment in shelterbelts was investigated. The methodology of predicting the value of an investment in a shelterbelt was developed and is presented in this study, The methodology was developed by modelling the shelterbelt system. The model, Shelterbelt Income Forecast Model, is presented as a means of predicting the value of an investment in a shelterbelt. A computer programme, PROGRAM/BELT, which calculates the values of an investment in a shelterbelt, is presented (in part) along with the model and documentation of the software for the Digital PDP 11/23 computer. A literature review on Economics and Shelterbelts is presented, along with a selected review of the literature which had been identified by the modelling process, as being relevant to the study. As model parameters and relationship between parameters were defined, experimentations were carried out to further assist in the development of the model, and in validation of the model. The critical model inputs identified were: shelter response and width of shelter area, width, and height of shelterbelt, shelterbe lt costs and revenues, Gross Margin of agri cultura1 production. For the mode1 to be va1 id for an area where the val ue of an investment in a shelterbelt is to be predicted, there are three basic assumptions: Winds cause a significant loss of production. The influence of a shelterbelt on agricultural production can be predicted. The growth of a shelterbelt can be predicted. PROGRAM/BELT was used to predict the value of an investment in shelterbelts on a Canterbury dryland pastoral farm at Westerfield. The predicted values were: IRR 0.56%, NPV, at 10% real interest rate, -$4529/km (-$112/ha). A sensitivity analysis was carried out and 30 PROGRAM/BELT data files (experimentations) are presented. The conclusions, based on the 30 PROGRAM/ BELT output data files are presented along with the conclusions for this study.