It all started in 2010 with an invitation from Robert to write a book chapter in the “Geographic and Global Issues” section of the second edition of the Encyclopedia of Biodiversity. Robert was one of the nine Associate Editors involved in this second edition together with Simon A. Levin, the Editor-in-Chief. To give to Caesar what is Caesar’s, I should say that this invitation was initially addressed to Jens-Christian Svenning, my postdoc supervisor and co-author on the paper. At that time, I was in the middle of my three-year postdoc position at Aarhus University in Denmark, working on plant macroecology and finalizing some of my PhD papers on elevational range shifts of forest plant species observed during the 20th century within the French mountains \citep{Lenoir_2008,Lenoir_2009,Lenoir_2010,Lenoir_2010a}. Given my early research on species redistribution, Jens-Christian asked me if I was interested in taking the lead of a book chapter on species range shifts under contemporary climate change, an offer that I immediately accepted. This book chapter \citep{Lenoir_2013} was intended to introduce the topic of climate-related species redistribution to students and scholars. Although this book chapter introducing the processes underlying climate-induced range shifts was not a systematic review, it provided fertile ground to yield a thorough synthesis and review on species range shifts under anthropogenic climate change. I remember quite well being overwhelmed by the increasing amount of literature published on this topic and I knew that a systematic review covering both the terrestrial and marine systems was missing at that time, although several highly cited and excellent meta-analyses focusing either on terrestrial or marine systems were already published.

Even before the actual publication of that book chapter in 2013, which happened far later than the formal acceptance of the manuscript, Robert, in his capacity as "Reviews and Synthesis" Editor for the Ecography journal asked me and Jens-Christian whether we would agree to prepare another manuscript on the same topic for the "Reviews and Synthesis" section of the journal. I guess Robert was rather happy about the outcome of the book chapter and anticipated a potential to expand this work into a proper review. I was so pleased and felt really honored to be invited again by Robert. Of course, I accepted the invitation which led me on a very long journey. It happened less than a year after I moved back to France to start my position as an Associate Professor in Biostatistics at the Jules Verne University of Picardy. I was pretty busy with the preparation of my statistic courses by then and was making little progress in reading and digesting all the scientific literature reporting species range shifts under contemporary climate change. Anyway, I wanted the review to be as exhaustive as possible for both the terrestrial and marine systems, although I was less comfortable with the literature from marine science given my background in terrestrial ecology. So, it took some time. Luckily, we were not starting from scratch but used the list of references selected by the most recent terrestrial and marine meta-analyses on the topic. However, to go beyond what was already known from these meta-analyses, we decided to perform a more traditional review focusing on the diversity of (i) biogeographic regions covered, (ii) taxonomic groups investigated and (iii) approaches used to report species range shifts instead of focusing on the overall magnitude and direction of species range shifts. After mining the scientific literature during two to three years using several search engines like Web of Science and Google Scholar, I managed, together with Jens-Christian, to gather a list of 245 references matching all our selection criteria and reporting species range shifts under anthropogenic climate change. I definitely read more than 1000 abstracts during that period and read all 245 references very thoroughly to extract general information on the studied geographic region, taxa and period as well as on the method used by the authors. I was so stubborn that I even painstakingly digitized the entire geographical region covered by each of the 245 selected references using Google Earth before storing all shapefiles (sometimes several shapefiles for a single reference covering several sites) in a geodatabase for subsequent analyses (for an example with one terrestrial reference and one marine reference, see Fig. \ref{339985}). This took me a hell of a lot of time. I am not sure I could do it again. But, by doing so, we could analyze some of the data we gathered and thus better highlight the current geographic, taxonomic and methodological research gaps. Based on these identified research shortfalls, we finally provided a working agenda, hopefully useful, for future research on species range shifts.