Bjørn Økland
Research Professor
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- Population dynamics of bark beetles
- Determinants of insect diversity in forests
- Climate change and insects
- Invasive species
Authors
Tomáš Hlásny Roman Modlinger Jostein Gohli Rupert Seidl Paal Krokene Iris Bernardinelli Simon Blaser Gediminas Brazaitis Gailenė Brazaitytė Eckehard G. Brockerhoff György Csóka Laura Dobor Maarten de Groot Mihai‐Leonard Duduman Massimo Faccoli Margarita Georgieva Georgi Georgiev Wojciech Grodzki Henrik Hartmann Anikó Hirka Gernot Hoch Tomasz Jabłoński Hervé Jactel Mats Jonsell Marija Kolšek Markus Melin Slobodan Milanović Constantin Nețoiu Mats Nieberg Bjørn Økland Milan Pernek Michaela Perunová Nick Schafstall Martin Schroeder Gottfried Steyrer Jozef Vakula Thomas Wohlgemuth Tiina Ylioja Andrew M. LiebholdAbstract
Ongoing shifts in climate and land use have altered interactions between trees and insect herbivores, changing biotic disturbance regimes. However, as these changes are complex and vary across host species, insect taxa, and feeding guilds, they remain poorly understood. We compiled annual records of forest insect disturbance from 15 countries in temperate and boreal Europe, spanning the period from 2000 to 2022. The dataset comprises 1361 time series characterizing the dynamics of 50 herbivorous insects. We used this dataset to test whether insect disturbance has systematically changed during the 23‐year period across host trees and feeding guilds, whether it varies along latitudinal and climatic gradients, and whether synchrony exists among species in the same guild or among species sharing the same host. Since 2000, borer disturbance was predominantly concentrated on gymnosperms, while defoliators impacted gymnosperms and angiosperms more evenly. While 85.8% of gymnosperm disturbance was inflicted by a single species, Ips typographus , the majority of disturbances to angiosperms were caused by six different species. Borer impact on gymnosperms has increased in the 21st century, while defoliator impact has decreased across both clades. In contrast to diverging temporal trends, disturbance was consistently greater in warmer and drier conditions across feeding guilds and host types. We identified significant synchrony in insect disturbance within host types and feeding guilds but not between these groups, suggesting shared drivers within guilds and host types. Increasing insect disturbance to gymnosperms may catalyze adaptive transformations in Europe's forests, promoting a shift from historical conifer‐dominated management to broadleaved trees, which are less affected by insect herbivores. Our findings reveal a diversity of trends in insect herbivory, underscoring the need to strengthen monitoring and research in order to better understand underlying mechanisms and identify emerging threats that may not be apparent in currently available data.
Authors
Bjørn ØklandAbstract
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Authors
Tomáš Hlásny Michaela Perunová Roman Modlinger Max Blake Gediminas Brazaitis György Csóka Maarten de Groot Mihai-Leonard Duduman Massimo Faccoli Margarita Georgieva Georgi Georgiev Wojciech Grodzki Henrik Hartmann Anikó Hirka Gernot Hoch Hervé Jactel Mats Jonsell Marija Kolšek Paal Krokene Markus Melin Slobodan Milanović Bjørn Økland Milan Pernek Gilles San Martin Martin Schroeder Rupert Seidl Jozef Vakula Tiina YliojaAbstract
Recent increases in forest damage across Europe have challenged national forestry sectors and threatened progress toward Europe’s climate and bioeconomy goals. Although developments in remote sensing now allow large-scale wall-to-wall monitoring of forest conditions, reliable damage assessments still require robust terrestrial data. Yet, existing data often remain inconsistent and fragmentarily distributed across institutions and countries. Based on consultations with national experts, we here provide an evaluation of national forest damage survey programmes in 19 European countries, identify obstacles that hinder more effective use of data, and formulate recommendations to overcome these barriers. We examined five aspects of national forest damage surveys: (i) legal and institutional frameworks, (ii) data acquisition methods, (iii) damage attribution, (iv) data quality and consistency, and (v) data accessibility. We found that half of the examined programs have changed protocols since 2000 and only 53 % of countries currently have survey programs covering their entire forest area. In 26 % of countries, legal constraints hamper data accessibility to the broader international community, while in 89 % data are available only in the respective national languages. In 84 % of countries, the absence of adequate metadata hinders the usability of the data without inside knowledge. Some of Central European countries operate the most consistent and open systems, while western and northern countries generally exhibited lower levels of openness and consistency. The implementation of coordinated structural changes in national programs that would enable consistent monitoring of forest damage at European level is unrealistic in the foreseeable future. However, certain critical gaps in data coverage, completeness, and consistency can be addressed through extensive data post-processing and integration with remote sensing. Overcoming barriers, such as limited awareness of the importance of transnational assessments, requires improved communication efforts and targeted funding programs. Establishing a coordination unit by leveraging existing policy processes in Europe appears essential to advancing these efforts.