Les défis de l'évaluation économique du patrimoine urbain des pays en développement / Methods for the economic valuation of urban heritage: a sustainability-based approach

Today, development actors see urban heritage as a resource for their territory, which is why they need to define its economic value. They seek to measure its economic value when the economic analysis provides traditional tools (use values only) too fuzzy to succeed in. This evaluation is a delicate exercise as such heritage is generally a complex reality, consisting of four interdependent economic, cultural, social and environmental dimensions. Our methodology leads us to propose an operational analysis grid in a coherent framework aimed at evaluating the economic interest of project in rehabilitating and promoting urban heritage and using different kind of indicators (both monetary and non-monetary; already available in the literature or to be locally collected), when the main limitation in economic evaluation of urban heritage in developing countries often stands in the non accessibility of the main data required. We first use an economic approach to urban heritage founded on its multidimensional character and try to transpose the evaluation methods used in the field of the environment and natural resources to the field of urban heritage. We also stress that the question of sustainability is essential in the case of urban heritage because, as for any heritage, it is a question of transmitting it to future generations, taking into account the interaction between the four different dimensions of urban heritage which are closely interlinked. Thus the economic evaluation of urban heritage has to consider its multi-dimensional aspects as well as its eminently dynamic character. Rather than a "weak sustainability approach" (Hartwick, 1977), we would here prefer an approach in terms of "strong sustainability" (Daly, 1990), assuming that the four different dimensions of heritage are complementary rather than substitutable according to certain thresholds beyond which the loss of one of the constituent dimensions of urban heritage would be irreversible. Then, we will build our own economic analysis grid of projects concerning urban heritage incorporating the main contributions of the approaches of Christian Ost (2009) and the IDB (2010) while adopting a holistic approach to urban heritage and specifying the definition of sustainability. We are here distinguishing the economic value in terms of the stock (capital) from the economic value of the flows of goods and services resulting from urban heritage. By analogy with the approach in terms of "genuine savings" (World Bank, 2006), and based on investment and deterioration flows, it is then possible to estimate "net accumulation rates" in the different dimensions of urban heritage and representing them, without necessarily applying a monetary evaluation, which could nonetheless have provided us with a single aggregate indicator. These four indicators are then summarised and presented on a "sustainability diagram" characterising the urban heritage situation in its four dimensions according to thresholds. We illustrate our urban heritage evaluation procedure from a methodological standpoint through the cases of two cities: Saint Louis du Senegal and Sousse (Tunisia), both on the World Heritage List, but with very different urban characteristics and histories. Using part of the information available, we first examine sustainability through the dynamics of accumulation or decumulation in the four main dimensions of urban heritage adopted in the two historic centres and conclude by identifying the thresholds and risks which might weight on heritage rehabilitation or renovation projects in the future for both of these cities.