This document aims to give an overview on current research approaches and propagation models for attenuation in vegetation, developed within the research group on "Antennas and Propagation –Lr" of the Instituto de Telecomunicac{c}~oes, in Portugal, and University of South Wales, in the UK, along with some results and comparisons with experimental data gathered at various scenarios and signal frequencies. This is a result of the work that has been done in Europe, particularly at the standardization bodies, in which contributions have been made to predictions models and measured data to the International Telecommunication Union – Radiocommunication Sector (ITU-R) recommendations on Propagation (P), i.e. ITU-R P.833-5. Topics will address formulation of possible extensions of the ITU-R P.833-9 based on recent results on analytical and experimental studies directed at the characterization and modeling of vegetation media effects on propagation and radio system design, including dynamic effects.