Spatio-temporal dynamics of agricultural and built-up areas in the Niaye area of Pikine urban wetland (Dakar, Senegal)

Abstract

The Niaye area of Pikine, a wetland with favorable physical and climatic conditions, is a rich and varied ecosystem that guarantees a supply of water and fertile soil, conducive to market gardening. This plays an important socio-economic role in the Dakar region. However, this sensitive and fragile ecosystem is often affected by poor farming practices. The aim of the study was to analyze the spatial evolution of agricultural areas and built-up areas in order to identify related environmental problems. Interview guides, aerial photographs from 1966 and 1978 and Digital Globe Over view 2 satellite images from 2004 and 2022 were used. The interview guides were used to obtain data on the management of the market gardening activity, and also to identify the environmental problems it generates. Satellite data processing revealed, through cartographic analysis, a progressive market gardening dynamic of +5.07%. In addition, the built-up area around the lake has increased by over 200%, resulting in a 68.4% decline in upland vegetation and a migration of market gardeners to the lake. This situation leads to the destruction of market garden crops in the rainy season as the water rises. What's more, the intensification of market gardening in response to the population's growing demand for vegetables has not failed to encourage bad practices, including the use of pesticides and sewage, which is a public health problem and a threat to the future of this wetland.