This research project aims at putting together a large-scale and long-term database on Eurasian biodiversity. The ECN database shall cover the territory of former USSR and Finland, and include a description of the environmental change (e.g. in terms of forest structure and climatic conditions) that has taken place in the past 50-100 years, as well as the population dynamic and phenological responses of species of mammals, birds, insects and vascular plants. As the field of ecology has a shortage of large-scale and long-term model systems, we consider already the task of compiling the ECN database as an objective by itself, not just a method for reaching the scientific objectives. The motivation for compiling the ECN database is that it makes it possible to address a number of basic and applied scientific research questions of fundamental relevance for the fields of ecology, conservation biology, and climate change research. In particular, we aim to use the database to disentangle the roles of abiotic and biotic factors in shaping patterns of species abundance, distribution, and spatio-temporal population dynamics. The applied objective of the research project is to develop methods for sustainable conservation and management under land use change and climate change, and to facilitate the implementation of these methods in real-world applications.