The culture by greenhouses has been one of the greatest agricultural transformations in the world, but especially in the southeastern Spanish. The main objective of this study was to analyze the transformation of the landscape and some of its environmental effects that, in the region of Cartagena-Mar Menor, have taken place in the recent decades as a result of the massive installation of greenhouses. We evaluated the areas occupied by greenhouses in some reference years, by digitizing orthophotos and statistical analysis. The results show a steady increase of the area occupied by greenhouses since 1980, related with the arrival of the waters from river Tajo to Segura. This type of intensive agriculture has very positive economic aspects, but show other negative from an environmental viewpoint: waste (solid and liquid), increasing the runoff and therefore flooding, or the possible contamination of the Mar Menor.