Relict species provide a unique opportunity to understand past and recent biogeographical and evolutionary processes. Zelkova abelicea (Ulmaceae), which is endemic to the island of Crete (Greece), is one of the most prominent Tertiary relict trees of the Mediterranean region. We collected distribution, threat and population structure data by reviewing literature and herbaria and through field surveys at 14 study plots throughout the range of the species. The present distribution of Z. abelicea is extremely fragmented. Although the total estimated number of individuals is relatively high, the populations are dominated by dwarf, severely browsed, non-flowering individuals. The population structure is asymmetric. At most, 5% of a plot's trees are large and fruit-bearing. The asymmetric structure is particularly pronounced in isolated and small populations. Based on its limited geographical range, the fragmented spatial pattern, and data on distribution and population structure, our study confirms that Z. abelicea is a threatened species (IUCN category Endangered). Our research aim is to promote the development of new approaches for the improvement of conservation strategies for Tertiary relict trees characterized by major local disjunctions.

Woodiness evolved in land plants approximately 400 Mya, and very soon after this evolutionary invention, enormous terrestrial surfaces on Earth were covered by dense and luxurious forests. Forests store close to 80% of the biosphere’s biomass, and more than 60% of the global biomass is made of wood (trunks, branches and roots). Among the total number of ca. 374,000 plant species worldwide, approximately 45% (138,500) are woody species—e.g., trees, shrubs or lianas. Furthermore, among all 453 described vascular plant families, 191 are entirely woody (42%). However, recent estimations demonstrate that the woody domination of our planet was even greater before the development of human civilization: 1.4 trillion trees, comprising more than 45% of forest biomass, and 35% of forest cover disappeared during the last few thousands of years of human dominance on our planet. The decline in the woody cover of Planet Earth did not decelerate during the last few centuries or decades. Ongoing overexploitation, land use and climate change have pushed ten thousand woody species to the brink of extinction. Our review highlights the importance, origin and past triumph of woody species and summarizes the unprecedented recent decline in woody species on our planet.