The black woodpecker reveals the hidden health of the country's southern temperate forests

The black woodpecker or Magellanic woodpecker (Campephilus magellanicus) is not only one of the most emblematic birds of the austral temperate forests of Chile, but also an ecological indicator of high value for assessing the health of these ecosystems. This is demonstrated by astudyconducted by national scientists, who analyzed the relationship between the foraging activity of this species and the diversity of beetles inhabiting decaying wood in living trees.

Published by the journal Insect Conservation and Diversity, the work evaluated whether the trees selected by woodpeckers for feeding concentrate a greater richness of saproxylic insects, key organisms for nutrient recycling and forest ecosystem functioning. The results confirmed that this is a strategy associated with the internal state of the wood and not a random behavior.

The study identified that the beetle communities present in excavated trees include various functional groups - a grouping of species that fulfill similar roles in an ecosystem - such as predators, fungivores, and borers. Species from these functional groups interact with each other and with the woody substrate, shaping an ecological network sensitive to environmental variations such as temperature, humidity, and forest structure.

"The abundance and taxonomic richness of predatory beetles, wood borers, and fungivores were higher in sections where Magellanic woodpeckers foraged. This behavior of the black woodpecker acts as a biological indicator of high value, a thermometer of forest health," said Silvio Crespin, research academic at theFaculty of Veterinary Medicine and Agronomyof theUniversidad de Las Américasand co-author of the article.

The exploration was carried out in 22 plots of native forests in southern Chile, where 132 living trees were analyzed, half with recent evidence of woodpecker foraging and the other half used as controls. Over 15 months, beetles were collected to systematically compare the biodiversity present in both types.

In total, 297 species of wood beetles were recorded, of which 257 were found in trunks excavated by woodpeckers, compared to 159 in the control group, confirming that their activity points to the areas of greatest biological diversity in the forest. "By monitoring the presence and foraging activity of the black woodpecker, we are obtaining an indirect and reliable measurement of the health of the entire decomposer insect community," Crespin noted.

The work brought together researchers from various Chilean and international institutions, originating from the ANID-Fondecyt 1231806 project at the Universidad de Santiago de Chile (USACH), with collaboration from the Instituto de Ecología y Biodiversidad (IEB), and CONAF, plus international support from the Laboratorio de Conservación Biológica y Ecología Aplicada del Instituto de Investigaciones Tropicales de El Salvador (El Salvador).

The ecological network of decaying wood

Saproxylic beetles, dependent on dead wood or wood in various stages of decomposition, represent a significant fraction of forest insect biodiversity. These organisms are responsible for nutrient release and the maintenance of complex trophic networks, which include fungi, other insects, and vertebrates.

According to the study, the beetle communities present in trees shape an ecological network sensitive to environmental variations such as temperature and humidity. The degree of wood decomposition also influences the diversity of guilds: while borers play a facilitating role in the initial stages, more advanced decomposition favors predators and fungivores, increasing the attractiveness for woodpeckers.

Crespin explains that parameters such as drought indices and tree diameter also modify the woodpecker's selectivity and alter the structure of the ecological network. "The stability of this relationship, which moves from dead wood, passes through insects, and culminates in the woodpecker, is extremely vulnerable to environmental pressures. When this chain is broken, the ecosystem's regeneration capacity is directly impacted."

Implications for forest conservation

The results have direct implications for conservation and management strategies of the austral temperate forests, the researchers suggest. By confirming that the Magellanic woodpecker acts as an indicator of saproxylic beetle diversity, they propose its use as an umbrella species to protect microorganisms of decaying wood, as well as organisms that use microhabitats created in dead wood by the combined effect of insects and woodpeckers.

According to Silvio Crespin, the findings warn that forest degradation and climate change exert control from the base of these ecological networks, accelerating certain decomposition processes but putting at risk species that sustain ecosystem functioning. "Decaying wood is not 'waste' or a risk to be removed. It is a vital resource that drives biodiversity and ecosystem health." In fact, Law No. 20,283 on native forest recovery does not establish the levels of dead wood that are critical for the conservation of saproxylic species such as the woodpecker, decomposer fungi, and the beetles that live in wood.

The study suggests that forest policies incorporate this knowledge, promoting the conservation of old trees with internal deterioration, as well as monitoring post-excavation succession to better understand the role of the black woodpecker as an ecosystem engineer. In the context of climate change, protecting this species will allow monitoring of invisible ecological processes to assess forest health.

Source:La Tercera