Summary: We show that the population ecology of the 9‐ to 10‐year cyclic, broadleaf‐defoliating winter moth (Operophtera brumata) and other early‐season geometrids cannot be fully understood on a local scale unless population behaviour is known on a European scale. Qualitative and quantitative data on O. brumata outbreaks were obtained from published sources and previously unpublished material provided by authors of this article. Data cover six decades from the 1950s to the first decade of twenty‐first century and most European countries, giving new information fundamental for the understanding of the population ecology of O. brumata. Analyses on epicentral, regional and continental scales show that in each decade, a wave of O. brumata outbreaks travelled across Europe. On average, the waves moved unidirectionally ESE–WNW, that is, toward the Scandes and the Atlantic. When one wave reached the Atlantic coast after 9–10 years, the next one started in East Europe to travel the same c. 3000 km distance. The average wave speed and wavelength was 330 km year⁻¹ and 3135 km, respectively, the high speed being incongruous with sedentary geometrid populations. A mapping of the wave of the 1990s revealed that this wave travelled in a straight E–W direction. It therefore passed the Scandes diagonally first in the north on its way westward. Within the frame of the Scandes, this caused the illusion that the wave moved N–S. In analogy, outbreaks described previously as moving S–N or occurring contemporaneously along the Scandes were probably the result of continental‐scale waves meeting the Scandes obliquely from the south or in parallel. In the steppe zone of eastern‐most and south‐east Europe, outbreaks of the winter moth did not participate in the waves. Here, broadleaved stands are small and widely separated. This makes the zone hostile to short‐distance dispersal between O. brumata subpopulations and prevents synchronization within meta‐populations. We hypothesize that hostile boundary models, involving reciprocal host–herbivore–enemy reactions at the transition between the steppe and the broadleaved forest zones, offer the best explanation to the origin of outbreak waves. These results have theoretical and practical implications and indicate that multidisciplinary, continentally coordinated studies are essential for an understanding of the spatio‐temporal behaviour of cyclic animal populations.

There is no sign of saturation in accumulation of alien species (AS) introductions worldwide, additionally the rate of spread for some species has also been shown to be increasing. However, the challenges of gathering information on AS are recognized. Recent developments in citizen science (CS) provide an opportunity to improve data flow and knowledge on AS while ensuring effective and high quality societal engagement with the issue of IAS (Invasive Alien Species). Advances in technology, particularly on-line recording and smartphone apps, along with the development of social media, have revolutionized CS and increased connectivity while new and innovative analysis techniques are emerging to ensure appropriate management, visualization, interpretation and use and sharing of the data. In early July 2018 we launched a European CO-operation in Science and Technology (COST) Action to address multidisciplinary research questions in relation to developing and implementing CS, advancing scientific understanding of AS dynamics while informing decision-making specifically implementation of technical requirements of relevant legislation such as the EU Regulation 1143/2014 on IAS. It will also support the EU biodiversity goals and embedding science within society. The Action will explore and document approaches to establishing a European-wide CS AS network. It will embrace relevant innovations for data gathering and reporting to support the implementation of monitoring and surveillance measures, while ensuring benefits for society and citizens, through an AS CS European network. The Action will, therefore, increase levels of participation and quality of engagement with current CS initiatives, ensuring and evaluating educational value, and improve the value outcomes for potential users including citizens, scientists, alien species managers, policy-makers, local authorities, industry and other stakeholders.

Non-native pests, climate change, and their interactions are likely to alter relationships between trees and tree-associated organisms with consequences for forest health. To understand and predict such changes, factors structuring tree-associated communities need to be determined. Here, we analysed the data consisting of records of insects and fungi collected from dormant twigs from 155 tree species at 51 botanical gardens or arboreta in 32 countries. Generalized dissimilarity models revealed similar relative importance of studied climatic, host-related and geographic factors on differences in tree-associated communities. Mean annual temperature, phylogenetic distance between hosts and geographic distance between locations were the major drivers of dissimilarities. The increasing importance of high temperatures on differences in studied communities indicate that climate change could affect tree-associated organisms directly and indirectly through host range shifts. Insect and fungal communities were more similar between closely related vs. distant hosts suggesting that host range shifts may facilitate the emergence of new pests. Moreover, dissimilarities among tree-associated communities increased with geographic distance indicating that human-mediated transport may serve as a pathway of the introductions of new pests. The results of this study highlight the need to limit the establishment of tree pests and increase the resilience of forest ecosystems to changes in climate.

SEEFOR - South-East European Forestry