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Azorean study reveals that native insects are finding unexpected refuge in exotic forests

A new study led by researchers from the University of the Azores and the Centre for Ecology, Evolution and Environmental Changes (cE3c) has uncovered that several indigenous insect and spider species of the Azores have managed to persist in exotic forests dominated by non-native trees such as Cryptomeria japonica and Pittosporum undulatum. The findings challenge conventional assumptions that these human-made forests are ecological deserts for native biodiversity.

Published in Global Ecology and Conservation (Elsevier), the paper—“Beyond native habitats: Indigenous arthropods adapted to mid-elevations find refuge in exotic forests”—demonstrates that mid-elevation exotic forests on Terceira Island can still harbor a remarkable diversity of indigenous arthropods. Using standardized long-term sampling methods, including SLAM and pitfall traps, the authors recorded 85 indigenous species (including 22 endemics), 65 of which were detected at least once in exotic forests.

“We were surprised to find that many native species still survive in these transformed ecosystems,” says lead author Sébastien Lhoumeau, a Ph.D. researcher at the University of the Azores. “Species that historically lived at mid-elevations appear particularly resilient and capable of persisting even in exotic stands.”

Elevation matters more than traits

Through detailed modelling of ecological and biogeographical traits, the researchers identified elevation as the main factor explaining which species occur in exotic forests. Species adapted to mid-elevation habitats (300–500 m above sea level) were the most abundant, while high-elevation specialists were almost entirely absent. Interestingly, the expected influence of body size, dispersal ability, or trophic guild was not significant.

“The persistence of these mid-elevation species reflects a kind of ecological memory of the landscape,” explains co-author Paulo A.V. Borges. “Before human colonization, native forests extended to lower altitudes. Many of these species still carry the legacy of that distribution.”

Conservation opportunities in unexpected places

The study highlights the potential role of exotic forests as transitional refuges for native biodiversity in highly transformed island landscapes. Although these habitats cannot replace native forests, they may serve as biological reservoirs and stepping stones that facilitate recolonization during restoration efforts. The authors argue that some exotic forest patches—often located outside protected areas and on private lands—should be recognized as key biodiversity areas or micro-reserves.

“Our message is not to replace native forests with exotics,” adds co-author Guilherme Oyarzabal, from the MACRISK project. “But rather to recognize that even altered habitats can still contribute to biodiversity recovery if managed properly.”

The research supports current European efforts under the EU Nature Restoration Law, which calls for the restoration of degraded ecosystems by 2030. In the Azores, integrating exotic forest management with native forest restoration could help prevent the extinction of several endemic species and maintain ecosystem functions such as pollination and nutrient cycling.

Funding and collaborations

This research was funded by the Government of the Azores, FCT – Fundação para a Ciência e a Tecnologia, and the Biodiversa+ BioMonI project (“Biodiversity monitoring of island ecosystems”). The work forms part of a long-term monitoring initiative led by the Azorean Biodiversity Group (cE3c/UAc).

Reference:
Lhoumeau, S., Oyarzabal, G., & Borges, P.A.V. (2025). Beyond native habitats: Indigenous arthropods adapted to mid-elevations find refuge in exotic forests. Global Ecology and Conservation, 64, e03935. https://doi.org/10.1016/j.gecco.2025.e03935

https://www.sciencedirect.com/science/article/pii/S2351989425005372?viaihub