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This thesis is concerned with analysing the interactions between smallholder sheep farming systems and the sustained maintenance of communal grazing resources in the temperate region of Mexico. The study was carried out in the parish of Coajomulco, which is located in the mountainous region south of Mexico City. Sheep production is a traditional agricultural activity in the region and extensive grazing is practised in the parish's communal forest. In 1988 the area was decreed as protected by the Ministry of Environment, and agricultural practices were highly regulated. Although sheep flocks could still have access to the forest, the establishment of an exclusion zone resulted in the inability of sheep farmers to make use of 48 % of the communal grazing area. Thus, the objectives of this thesis were concerned with finding a way of enhancing the development of the local smallholder sheep farming whilst concomitantly protecting the forest ecology. The ultimate objective of this thesis was to develop a spatial optimisation model for the grazing management of the communal land. This model produced the optimal distribution of flocks in time and space according to the characteristics of both the grazing resources and the sheep population. Prior to the development of the optimisation model, it was necessary to characterise the basic elements that affected the supply and demand of forage. Thus, under a farming systems research framework, the plant and animal elements of the farming system were characterised. The managerial and biological influences that defined the sheep grazing patterns were investigated and their resulting effects discussed. Participatory techniques were included as the core of the characterisation methodology. Findings derived from the characterisation were utilised to assist in the development of a geographical information system (GIS) and the application of biological simulation models. Two models, one that simulated flock dynamics and another that simulated sheep performance, were used. Subsequently, a two-way link was established between the simulation models, the GIS and the optimisation model.

Bibliography: pages 191-198. volume 1, thesis. volume II, appendices. / The ancestors of Geographical Information Systems (GIS) were first developed in the early 1960's as a computer mapping mechanism but with the development of the Canada Geographical Information System the base was set for a powerful spatial analytical tool that could be used in a wide range of applications from business through to map analysis and archaeology. GIS have been used in terrestrial archaeology with success for a number of years and have started to move into the maritime archaeological field, however, little has been published on the use of GIS in the regard to the latter. On 24 May 1697, the VOC retourschip, Oosterland, was wrecked in Table Bay off Paarden Eiland, Cape Town, South Africa. With its discovery by sport divers in 1988, an ideal opportunity represented itself for the first scientific excavation of a shipwreck in southern Africa. With the development of the project, it was decided that GIS would be applied to surveyed artefacts recovered over the first fieldwork seasons. Early efforts, in 1991 and 1994, set up a GIS for this site that succeeded in plotting and mapping artefact groups selected by the user but failed in creating a system through which advanced spatial analysis could be undertaken. Because of the simplicity of the 1991 and 1994 versions of the Oosterland GIS and the fact that the format of analysis was changed from the ARCJINFO to ArcView GIS, it was necessary to re-enter all of the data. This was achieved by creating tables in the Tables feature of ArcView that contained x and y positions for all of the surveyed artefacts. Positioning of artefacts was achieved through a True Basic program that converted on-site tape measurements into map co-ordinates. Other features included in these tables were artefact numbers, names, a classification and a description of each artefact created specifically for use in this system. Once data had been captured it was plotted and spatial analysis that hoped to test the viability and accuracy of the system was performed. These tests included the orientation of the wreck on the sea floor, and assigning ownership of personal trade items within the artefact assemblage to specific people or areas on board the ship. Tests also examined the position of artefacts whose place on the working vessel were known from historical documentation and related them to other artefacts present in their immediate neighbourhoods. This system appears to possess the potential for being a powerful analytical tool which can be easily updated to include more advanced analysis and adapted to incorporate other wreck sites. Finally, this system has enormous potential as an educational tool that can be used to raise awareness of the importance of historically significant wrecks.

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