Biodiversity Conservation is a priority issue for the scientific community, and a main subject in the Biology and Geology curriculum at secondary school level in Spanish Educational System. In the present didactic proposal, we use the demographic monitoring of an endangered plant species to illustrate a research tool for estimates of biodiversity loos in nature, the local endemic Astragalus tremolsianus Pau. The aim of the proposal is to bring students closer to a real experience, which brings together knowledge of Biology, Algebra and Trigonometry, through Information and Communication Technologies (ICTs). Showing a census to monitor the populations of a threatened high mountain flora species into the classroom is an innovative teaching activity that combines and uses knowledge from different disciplines, as well as demonstrating a real application of the knowledge acquired. The use of mathematical tools encompasses a number of skills that require the application of mathematical principles and processes in the scientific context. The introduction of the structure of scientific texts is another positive aspect of this didactic experience.