The need to develop and provide integrated observation systems to better understand and manage global and regional environmental change is one of the major challenges facing Earth system science today. In 2008, the German Helmholtz Association took up this challenge and launched the German research infrastructure TERrestrial ENvironmental Observatories (TERENO). The aim of TERENO is the establishment and maintenance of a network of observatories as a basis for an interdisciplinary and long-term research programme to investigate the effects of global environmental change on terrestrial ecosystems and their socio-economic consequences. State-of-the-art methods from the field of environmental monitoring, geophysics, remote sensing, and modelling are used to record and analyze states and fluxes in different environmental disciplines from groundwater through the vadose zone, surface water, and biosphere, up to the lower atmosphere. Over the past 15 years we have collectively gained experience in operating a long-term observing network, thereby overcoming unexpected operational and institutional challenges, exceeding expectations, and facilitating new research. Today, the TERENO network is a key pillar for environmental modelling and forecasting in Germany, an information hub for practitioners and policy stakeholders in agriculture, forestry, and water management at regional to national levels, a nucleus for international collaboration, academic training and scientific outreach, an important anchor for large-scale experiments, and a trigger for methodological innovation and technological progress. This article describes TERENO’s key services and functions, presents the main lessons learned from this 15-year effort, and emphasises the need to continue long-term integrated environmental monitoring programmes in the future.

The development of several large-, ‘continental’-scale ecosystem research infrastructures over recent decades has provided a unique opportunity in the history of ecological science. The Global Ecosystem Research Infrastructure (GERI) is an integrated network of analogous, but independent, site-based ecosystem research infrastructures (ERI) dedicated to better understand the function and change of indicator ecosystems across global biomes. Bringing together these ERIs, harmonizing their respective data and reducing uncertainties enables broader cross-continental ecological research. It will also enhances the research community capabilities to anticipate and address future global scale ecological challenges to the planet. Moreover, increasing the international capabilities of these ERIs goes beyond their original design intent, and is an unexpected added value of these large national investments. Here, we identify specific global grand challenge areas and research trends to advance the ecological frontiers across continents that can be addressed through the federation of these cross-continental-scale ERIs.

Understanding, predicting, and responding to a rapidly changing Arctic requires sustained observations that capture variability and transformative change of the Arctic systems with all its major components. A key challenge for researchers, Arctic communities, and others tasked with effective responses to such change is to achieve structured coordination of numerous individual observing activities and networks. These have different regional and thematic foci. Many are driven from the bottom-up by research interests, while others are mission-oriented operational networks. The Arctic Observing Summit (AOS) is an effort that seeks to help coordinate such disparate activities and support efforts such as the Sustaining Arctic Observing Networks (SAON) initiative. We report on progress as part of an AOS 2018 working group focused on implementation and optimization of sustained observations. Drawing on the Framework on Ocean Observations, our group identified effective approaches and barriers to integration of different observation requirements and activities/platforms into a coherent observing framework. Case studies for benthic communities, sea ice prediction, and permafrost highlighted the importance of allowing for independently driven activities to coalesce into a uniform framework. This in turn requires clearly defined requirements that ideally serve multiple societal benefits. Such clear definitions also aid private-public partnerships and the development of new observing system business models. Prerequisite to better coordination is a comprehensive, international assessment that describes the current set of systems, community-based networks, sensors, networks, and surveys that are used to observe the Arctic today. Pieces of such an endeavor are starting to emerge, and SAON may serve as a home for integrating and building upon these pieces. Essential to this goal is the development of a knowledge map that collates and connects observing resources to societal benefits, helps identify and prioritize essential variables, data management needs, and critical products and services. The AOS 2018 calls for the launch of an optimization and implementation team of experts that would conduct such an effort under the auspices of SAON. We explore different elements of such a team’s portfolio of tasks.