A working group was established by the EUFORGEN Steering Committee to develop the pan-European genetic conservation strategy for forest trees. For each species, the strategy calls for a core network of dynamic conservation units. These units are not interconnected by geneflow, but together capture the current genetic diversity across the European continent. Method: The working group selected 14 pilot tree species representing four categories, depending on their geographical distribution (wide vs restricted) and their ecology (stand-forming vs scattered). The group also created a map of eight environmental zones by amalgamating some of the zones of an accepted environmental zoning classification for Europe. It then sought to identify at least one conservation unit per country for each environmental zone in that country, using a set of criteria to determine the most appropriate unit. This process resulted in the identification of 1836 dynamic conservation units, covering a total area of 205,803 ha and encompassing 2173 populations. Gaps in conservation efforts: To identify gaps in existing conservation efforts, the group compared species distribution maps in each environmental zone in each country with the location of the conservation units. Any species with no unit in an appropriate environmental zone in that country was recorded as a gap, and units were also noted where there was an information gap in the EUFGIS database. Genetic Conservation Strategy: The EUFORGEN Steering Committee will promote implementation, identify additional units once gaps have been filled and will monitor progress. A particular concern is the effect of climate change on phenology, but the detailed effects on long-lived tree species are likely to be variable, complex and difficult to predict. As a result, conservation should focus on the most vulnerable populations and species, for example those near the edge of their environmental limits, which often harbour high genetic diversity. Monitoring such populations should help to reveal key changes in a timely fashion, and management may then be needed to mitigate the effects of climate change.