Ambient ozone – New threat to birds in mountain ecosystems?

• Published in: The Science of the total environment 2023-06, Vol.876, p.162711-162711, Article 162711
• Main Authors: Reif, Jiří, Gamero, Anna, Flousek, Jiří, Hůnová, Iva
• Format: Article
• Language: English
• Subjects: Air Pollutants - analysis; Air Pollutants - toxicity; Air pollution; Air Pollution - analysis; Alpine zone; Altitudinal gradient; Animals; Birds; Ecosystem; Ground-level ozone; Humans; Ozone - analysis; Ozone - toxicity; Population growth rate; Upland birds
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2023.162711

Mountain ecosystems are inhabited by species with specific characteristics enabling survival at high altitudes, which make them at risk from various pressures. In order to study these pressures, birds represent excellent model organisms due to their high diversity and position at the top of food chains. The pressures upon mountain bird populations include climate change, human disturbance, land abandonment, and air pollution, whose impacts are little understood. Ambient ozone (O3) is one of the most important air pollutants occurring in elevated concentrations in mountain conditions. Although laboratory experiments and indirect course-scale evidence suggest its negative effects on birds, population-level impacts remain unknown. To fill this knowledge gap, we analysed a unique 25-years long time series of annual monitoring of bird populations conducted at fixed sites under constant effort in a Central European mountain range, the Giant Mountains, Czechia. We related annual population growth rates of 51 bird species to O3 concentrations measured during the breeding season and hypothesized (i) an overall negative relationship across all species, and (ii) more negative O3 effects at higher altitudes due to increasing O3 concentration along altitudinal gradient. After controlling for the influence of weather conditions on bird population growth rates, we found an indication of the overall negative effect of O3 concentration, but it was insignificant. However, the effect became stronger and significant when we performed a separate analysis of upland species occupying the alpine zone above treeline. In these species, populations growth rates were lower after the years experiencing higher O3 concentration indicating an adverse impact of O3 on bird breeding. This impact corresponds well to O3 behaviour and mountain bird ecology. Our study thus represents the first step towards mechanistic understanding of O3 impacts on animal populations in nature linking the experimental results with indirect indications at the country-level. [Display omitted] •Ambient ozone is a widespread pollutant in mountains, its concentration increases with altitude.•Ambient ozone impacts on bird populations have not been documented up to now.•Analysis of relationships between bird population growth rates and ambient ozone concentration.•Negative effects observed in alpine birds indicating the adverse ozone impacts on their breeding.•Ozone adds another pressure to existing threats of mountai