Dear colleagues, We are glad to announce the session B5a Climate Change, Environment and Conservation: Challenges from the Analysis of Tree Rings , which will be held on the occasion of the XXV IUFRO World Congress, Curitiba, Brazil, 29 Sept - 5 Oct 2019 . The purpose of the session is to bring together the community interested in studies of tree rings in relation to environmental variability. As the tree-ring record expands both in time and forested areas, scientists are finding out more about long-term environmental variations, extremes, and trends. Even though dendrochronology has made (and will continue to make) significant contributions to the understanding of forest biology and environmental dynamics, it is necessary to pose challenges to extend these studies to vast areas that have been little explored so far, such as the tropics and subtropics. The global dynamics of the atmosphere, the impact this has on the dynamics and biodiversity of forests and the benefits they bring to society, highlight the need for dendrochronological contributions in providing key information to assess the impact of climate change on the biological systems of the earth and improve the design of policies to mitigate human influence on the climate and the conservation of ecosystems. We encourage worldwide contributions of tree-ring analysis that look at recent and/or past climatic changes, at seasonal or longer temporal scales. The session will offer the opportunity to present new research findings and incorporate new methodologies to enhance our understanding on the different factors that affect the wood formation in different bioclimatic regions. Abstracts deadline is 31 December 2018 and Congress registration and abstract submission is available at: [ http://iufro2019.com/abstracts-submission/ | http://iufro2019.com/abstracts-submission/ ] Please, feel free to disclose this information among all colleagues. We hope to see you in Curitiba! Our best regards, Fidel Roig, Mario Tomazello, Patricia Povoa de Mattos ( organizers )