Nocturnal arthropod occurrences across Natura 2000 protected areas of Madeira Island (Portugal)

A standardised baseline survey was conducted to document terrestrial arthropod occurrences across nine Natura 2000 protected areas on Madeira Island, Portugal. The dataset provides georeferenced occurrence and abundance records intended to support long-term monitoring of nocturnal communities, particularly under future assessments of artificial light at night. Nocturnal Lepidoptera received greater sampling and taxonomic identification effort than the other surveyed arthropod groups.

The project was the baseline biodiversity survey component of the LIFE Natura@night initiative and was designed to record species occurrences before later evaluations of artificial light at night. It was not an experiment measuring the effects of artificial lighting. Instead, its purpose was to establish an inventory of nocturnal arthropods in protected areas and provide standardised baseline data for subsequent monitoring. Although the sampling covered several arthropod groups, the greater sampling and taxonomic effort applied to nocturnal Lepidoptera made them the focus of the associated analyses.

Madeira Island contains 12 terrestrial Natura 2000 sites covering approximately 35% of its land area. Nine sites were sampled: SCI Cabo Girão, SCI Caniço de Baixo, SCI Machico, SCI Pico do Facho, SCI Porto Novo, SAC Pináculo, SAC Maciço Montanhoso Central da Ilha da Madeira, SPA/SAC Ponta de S. Lourenço and SPA/SAC Laurissilva da Madeira. The selected sites encompassed coastal habitats, dry shrublands, agricultural mosaics, exotic forests, native laurissilva forest and high-altitude mountain ecosystems. Three other terrestrial Natura 2000 sites—Achadas da Cruz, Ilhéu da Viúva and Moledos–Madalena do Mar—were excluded because of logistical constraints.

A total of 48 sampling points were established across the nine protected areas, with points separated by at least 250 metres to maximise spatial independence. Fieldwork comprised campaigns in late summer 2022 and spring 2023, producing 68 sampling events. During the second campaign, researchers revisited selected locations that had yielded few specimens during the first survey because of unfavourable weather conditions, reduced vegetation cover or both. Two additional sampling sites were established in 2023 to improve coverage of the protected areas surveyed.

Each sampling event used two complementary arthropod trapping methods. UV Heath light traps were used to sample nocturnal Lepidoptera, the primary target group of the LIFE Natura@night project and the group for which standardised comparisons among sites were required. Wine-rope bait traps provided a complementary method intended to detect species that are weakly attracted to artificial light or not attracted to it. This combination was intended to reduce sampling bias associated with reliance on light traps alone and improve the completeness of the inventory.

Environmental conditions were recorded during each sampling event, including temperature, relative humidity, cloud cover, wind intensity and sky darkness assessed with the Bortle scale. Sampling was not conducted during periods of strong winds, rainfall or high humidity because these conditions can reduce insect activity and trap efficiency. These restrictions also mean that the compiled dataset represents sampling conducted under specified weather and environmental conditions rather than uninterrupted monitoring across all conditions.

The dataset is intended to supply occurrence and abundance information for terrestrial arthropods and establish a baseline for monitoring Madeira’s nocturnal communities. Such baseline records are particularly relevant on an oceanic island whose arthropod fauna includes more than 3,400 insect taxa and more than 750 endemic species, according to the background cited by the dataset. The authors note that important gaps remain in knowledge of the distribution, abundance and ecology of many Madeiran insects and that relatively few species have been assessed for extinction risk.

The work also provides a standardised, Darwin Core-formatted biodiversity record curated by Elisa Teixeira, Mário Boieiro and Paulo A.V. Borges. The field and identification team was divided among project planning and sampling design, fieldwork, specimen identification and data curation. The published resource therefore combines information about the survey’s geographic coverage, sampling design, environmental conditions, complementary trapping methods and taxonomic treatment, together with the associated occurrence and abundance data.

Because the supplied material describes a dataset and its baseline survey design rather than a comparative analysis of artificial light at night, it does not report an estimated effect of lighting on arthropod abundance, behaviour or community structure. Its supported contribution is the establishment and publication of a large-scale standardised inventory across selected Natura 2000 protected areas of Madeira Island. The stated role of this baseline is to support subsequent assessment of nocturnal arthropod responses to artificial light exposure within the LIFE Natura@night project.

Subject of Research: Baseline inventory and sampling design for nocturnal arthropods in Madeira Natura 2000 protected areas

Article Title: Nocturnal arthropod occurrences across Natura 2000 protected areas of Madeira Island (Portugal)

Article References: Teixeira, E., Costa, T., Gouveia, C., Vieira, V., Boieiro, M., & Borges, P. (2026). Nocturnal arthropod occurrences across Natura 2000 protected areas of Madeira Island (Portugal). Biodiversity Data Journal, 14, Article e209141. https://doi.org/10.3897/bdj.14.e209141

Image Credits: AI Generated

DOI: 10.3897/BDJ.14.e209141

Keywords: Madeira Island, nocturnal arthropods, Lepidoptera, Natura 2000, biodiversity inventory, artificial light at night, light trapping, bait trapping, LIFE Natura@night, Nocturnal, arthropod, occurrences