A collective effort is needed to create the environmental research infrastructure for answering pressing questions in a world of rapid social, economic and environmental change. The overall aim of the eLTER project is to advance the European network of Long-Term Ecosystem Research sites and socio-ecological research platforms to provide highest quality services for multiple use of a distributed research infrastructure. eLTER's major objectives and methods are to: (1) identify user needs for the research infrastructure in relation to major societal challenges through consultations with scientific, policy and business stakeholders and horizon scanning; (2) streamline the design of a cost-efficient pan-European network, able to address multiple ecosystem research issues, in collaboration with related global and European research infrastructures, e.g. LifeWatch; (3) develop the organisational framework for data integration and enable virtual access to the LTER data by enabling data publishing through distributed Data Nodes and by providing access to data on key research challenges through a Data Integration Platform; (4) foster the societal relevance, usability and multiple use of information, data and services through new partnerships with the providers of remotely sensed data, analytical services and scenario testing models, and via the adoption of new measurement technologies. The LTER-Europe network and the European Critical Zone community will collaborate to achieve these goals. 162 sites in 22 countries will provide data on long-term trends in environmental change, some reaching back 100 years. Test cases using these data will address a range of environmental and social issues to push innovation in network level services and steer conceptual developments. The envisaged 'LTER Infrastructure' will enable European-scale investigation of major ecosystems and socio-ecological systems, and support knowledge-based decision making at multiple levels.