Past processes and events may have an important influence on contemporaneous ecological patterns, including current human impacts on landscapes and organisms. In spite of that, most of the ecological knowledge has been built upon short-term studies, which very rarely exceed one decade. Ecology and Conservation Biology have an important lack of historical approaches, a deficiency that may become a hindrance for the management of natural systems. In this talk I will present examples of how historical information on the distribution of organisms can be used to address ecological questions. Analyses are mainly based on two important Spanish historical written sources from the 16th century and the 19ht century, but also use archival information. I address questions related to the history of biological invasions, habitat loss and the impacts of global warming focusing on animal populations in freshwater systems. The outputs of ecological research based on historical data become useful tools for present-day biodiversity conservation planning and actions-