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Has North Africa turned too warm for a Mediterranean forest pest because of climate change?


Climate warming is inducing dramatic changes in species distribution. While many studies report the poleward range expansion of some species, some others report the range retraction and extinction risk of other species. Here we explore how climate warming affects the southern edge in North Africa of the pine processionary moth, Thaumetopoea pityocampa, which is a model insect currently expanding northwards and toward higher elevation in Europe. This Mediterranean forest insect was found in southern Tunisia until 2003. Field surveys were conducted to map the current southern edge of the species in Tunisia. Pheromone traps were installed on a north-south gradient, a translocation experiment of egg masses was conducted on this gradient, and local temperature change was analyzed. We thus proved that the pine processionary moth has disappeared from southern Tunisia, and that no more adult males were actually flying there. We also found a decrease of egg hatching and of the proportion of individuals able to reach larval stages along this gradient, while daily minimal and maximal temperatures globally increased. Furthermore, we showed that daily maximal and minimal temperatures as well as indices of extremely high temperatures have substantially increased during the study period (1980–2019). This study reveals the retraction of the pine processionary moth from southern Tunisia due to higher mortality rates that could be attributed to a significant local warming. The role of other factors (mainly the response of host trees and natural enemies to climate change) may amplify this direct effect and should be further explored.

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Data availability

Most of the datasets are provided in the article and supplementary material. Other datasets are available from the corresponding author on request.

Code availability

The R code of analyses is available from the corresponding author on request.


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We are grateful to Jérôme ROUSSELET (INRAE-URZF, Orléans, France) for insightful advice on mapping the edge of species distribution and translocation experiment, to Olfa EZZINE and Samir DHAHRI (INRGREF, Tunis, Tunisia) for general discussions and support in the frame of the PhD of Asma BOUROUGAAOUI, and to Adel BEN ABADA (INRGREF, Tunis, Tunisia) for his valuable help in the field. Pheromone traps and protective suits were kindly provided by Jean Claude MARTIN (INRAE-UEFM, Avignon, France). The distribution of pine stands was kindly provided by the General Direction of Forests in Tunis, and a part of the temperature datasets by the National Institute of Meteorology (INM) in Tunis.


This study was supported by funding from the University of Carthage (Tunisia): the University provided two grants to Asma BOUROUGAAOUI to spend her internships (two months/grant) at INRAE-URZF in France in 2018 and 2019 in the frame of her PhD. It was also supported by the ANR project PHENEC (grant number 19-CE32-0007-01).

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CR and MBJ designed the study. AB conducted the field experiments, the laboratory analysis, and the statistical analyses. CR and MBJ supervised her work. AB, MBJ, and CR wrote and revised the article.

Corresponding author

Correspondence to Christelle Robinet.

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This study was conducted on an insect species (the pine processionary moth, Thaumetopoea pityocampa), which is a pest species commonly controlled. In addition, this is a model species for science which has been exempted from any declaration regarding the Nagoya protocol.

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The authors of this article consent to publish the study.

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The authors declare no competing interests.

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Bourougaaoui, A., Ben Jamâa, M.L. & Robinet, C. Has North Africa turned too warm for a Mediterranean forest pest because of climate change?. Climatic Change 165, 46 (2021).

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  • Pine processionary moth
  • Thaumetopoea pityocampa
  • Climate warming
  • Range retraction
  • Pinus
  • Tunisia