Large-scale habitat model reveals a key role of large trees and protected areas in the metapopulation survival of the saproxylic specialist Cucujus cinnaberinus

Abstract

Deforestation for agricultural purposes and logging over centuries has resulted in a significant loss of forest cover and the deep structural and functional simplification of persistent European woodlands, which has led to a large-scale decline in biodiversity. Despite recent reforestation efforts in many regions of Europe, populations of numerous forest species remain unrecovered. Due to the loss of ecological continuity and the simplification of the ecosystem structure and functionality, the value of secondary forests in sustaining habitat specialists is being questioned. Here, we build a large-scale habitat suitability model to predict the current potential of forests to host populations of the flagship European saproxylic beetle Cucujus cinnaberinus. Our maximum entropy model revealed that the distribution of suitable habitats strongly corresponds to the occurrence of large and well-preserved forest complexes that are characterized by an ecological continuity of the stands. Among the analysed environmental variables, the mean tree diameter and distance to protected areas were the most important suitable habitat contributors. The optimum habitats were identified almost exclusively within some parts of the Carpathians and the northeastern part of the country, particularly in the Białowieża Forest, which include the best preserved European forests. Although a large number of small habitat patches was revealed across the country, these patches were highly scattered and had low predicted suitability. This study demonstrates that most woodlands are unsuitable for C. cinnaberinus, which points to the limited value of secondary forests for habitat specialists. Our findings emphasize the importance of large and intact forests with undisrupted ecological continuity as key areas for the persistence of the rare saproxylic beetle, which provokes questions about the effectiveness of reforestation as a tool for the conservation of forest habitat specialists.