By Professor P.M.Allen, IERC, Cranfield University, Bedford, UK
In collaboration with Professor A. Poulovassilis and his group at the Agricultural University of Athens, Greece
Project Sponsors: DGXII, Environment Programme.
(Part of the EU's Archaeomedes programme)
Traditionally, on the coastal plain around the city of Argos, cereals, fruit and vegetables, olives and variety of crops have been grown. Over recent years, however, there has been an substantial shift to irrigated crops offering higher yields and revenues. These developments have been favoured by various local, national and European agricultural policies, with price support for irrigated crops such as citrus fruits, and subsidies for irrigation infrastructures and investments.
The problem that arises concerns the potential desertification of the area, not only as a result of climatic change, but also as a result of this intensification process. The mechanism is that of over-exploitation of the aquifer, so that sea water and salt have been drawn into it and lead to the salination of the soil and to a reduction in the sustainability of agriculture. Policies that were designed perhaps to support the rural, agricultural economy have lead to the unintended consequence of greatly reduced agricultural potential and to and quite possibly wider social effects. As a response to this, artificial management of the aquifer has begun, and large investments in new water supply infrastructure have been made, although we have shown that other policy instruments could be used to affect the situation. Both the initial policies, and the reaction to their consequences have been implemented without the benefit of an overall understanding of the complex situation. The real aim of this project, therefore, is to provide such an understanding, as a contribution to generic "policy relevant" methodology to explore possible futures.
The Argolid study has consisted in developing a dynamic, integrated mathematical model linking the physical, biological and socioeconomic factors involved in the agricultural system and driving land-use. This model consists of a set of non-linear, differential equations (with a small time step) governing the changes in, and below, each small geographical zone: changes in rainfall, surface water, infiltration, aquifer height, the run-in and run-off of water on the surface and within the aquifer, and whether or not farmers are pumping water from the aquifer to irrigate their crops. Thus a hydrological model of ground water and salt movements is linked to the farmers needs for irrigation water, depending on their crop choices and the rainfall that is occurring. In turn, the model captures the farmers' decision making concerning the pattern of crop choice and land-use, depending of course on both changing economic factors such as prices and costs, as well as on the condition and type of soils and the costs of irrigation. This has been achieved by developing physical models of the real time dynamics of water flow, temperature and rainfall and combining them with a spatial socioeconomic model which uses parameters resulting for a detailed social enquiry. This is one of the unique features of the study. The social enquiry managed to elicit from farmers the reasons for their crop choices and decision concerning irrigation, the factors that would cause them to change these, and the time delays involved in implementing the decisions that they made. In this way a dynamic model capable of simulating the history of the Argolid was developed, and more importantly, the integrated model could be used to explore different possible future paths of the system under different policy options, and different scenarios concerning external economics, and climate change etc. The model displays many of the characteristic effects of a non-linear, spatial dynamic model containing multiple feedbacks. It shows a sensitivity to initial conditions, as well as the existence of thresholds for run-away processes of land salination and agricultural decline.
In the second phase of the project, effects at multiple spatial scales are being studied. This will provide the basis of a generic integrated framework linking: surface and underground hydrology; soil salinity, erodability and permeability; vegetation and crop growth and requirements; microclimate and climate; changed water supply infrastructure; farmer types and socioeconomic and risk factors affecting land-use decisions. In order to establish a generic approach, another site in Spain, in the Province of Alicante will be modelled, with the same integrated multi- scalar method, showing how such a systems model can provide a basis for the policy formulation process for many such areas in the Mediterranean countries, as well as helping to set the science research agenda.
Lemon M., Seaton R., and Park J., 1994, "Social Enquiry and the Measurement of Natural Phenomena: the Degradation of Irrigation Water in the Argolid plain", International Journal of Sustainable Development, World Ecology. 1, p206-220.
P.M.Allen, 1995 "Cities and Regions as Evolutionary Complex Systems", Prepared for the 9th European Colloquium on Theoretical and Quantitative Geography, Spa, Belgium 9-13th September, 1995. To appear in Geographical Systems, 1996
P.M.Allen, 1995, "Population Growth and Environment as a Self-organizing System", Prepared for the International Workshop on "Population, Environment and Society on the verge of the 21st Century", in Tel Aviv, 10-12th December, 1995. To be published in a book.
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Last Updated: 7th October 1996.