Dutch elm disease was detected nearly a hundred years ago in north-eastern France. Since then it has spread extensively to the point that it is considered to be one of the most destructive diseases ever found on woody plants, both in Europe and in north America. Other diseases have proved to be just as destructive such as chestnut blight once again in Europe and north America, or potentially just as damaging such as ash dieback in Europe. It therefore appeared worthwhile to try to learn some lessons from one of the oldest pandemics affecting a forest tree species. In actual fact, two pandemics of Dutch elm disease in succession were involved, attributed to two distinct fungi (Ophiostoma ulmi and then O. novo-ulmi) that developed in Europe. O. novoulmi, which at the end of the 1960s was responsible for the most severe pandemic, experienced rapid evolutionary changes via hybridization and horizontal gene transfers with other species. The aggressiveness of this fungus appears not to have subsided in the last fifty years and the amount of growing elm stock in French forests has diminished considerably but appears to have stabilized in the last ten years at between 2 and 4 million cubic metres, with young stems predominant according to data from the national Forest Inventory. Mortality in forests also appears to be relatively low, perhaps in connection with the drop in the population of its main vector (Scolytus scolytus), which is mainly reliant on adult tees. In spite of the drastic drop in elm populations, there is no study that shows any decrease in the genetic diversity of field populations in Europe. However, the introduction of an Asian species of elm that is resistant to Dutch elm disease in southern Europe has led, after hybridization and introgression, to irreversible changes in the genetic structures of native elms. In this area, human actions in the wake of the disease may have altered the genetic structure of elm populations more than the disease itself. Similarly, the effects of the two successive pandemics on the biodiversity associated with elms appear to be fairly limited according to the literature. These results are at odds with the alarmist view that predominated in the 1980s and which led to establishing a repository for elm genetic resources in the form of a collection of clones in the hopes of breeding resistant elms. no clone was found to be strongly resistant to Dutch elm disease but some of them, amongst those that were more prone to heal, could contribute to restoring hedgerows. In the 1990s, in situ conservation facilities for European white elm and mountain elm stands were set up in the framework of a network coordinated at the European level.