Listening to a changing landscape: Acoustic indices reflect bird species richness and plot-scale vegetation structure across different land-use types in north-eastern Madagascar. (January 2021)

• Record Type: Journal Article
• Authors: Dröge, Saskia; Martin, Dominic Andreas; Andriafanomezantsoa, Rouvah; Burivalova, Zuzana; Fulgence, Thio Rosin; Osen, Kristina; Rakotomalala, Eric; Schwab, Dominik; Wurz, Annemarie; Richter, Torsten; Kreft, Holger
• Is Part Of: Ecological indicators. Volume 120(2021)
• Publication Date: 2021-01
• Subjects: Acoustic indices -- Rapid biodiversity assessment -- Conservation -- Ecoacoustics -- Land-use change -- Madagascar; Environmental monitoring -- Periodicals; Environmental management -- Periodicals; Environmental impact analysis -- Periodicals; Environmental risk assessment -- Periodicals; Sustainable development -- Periodicals; 333.71405
• DOI: 10.1016/j.ecolind.2020.106929
• Languages: English
• ISSNs: 1470-160X

Abstract

Highlights: Ecoacoustics can increase time and cost efficiency in biodiversity assessments. We applied four acoustic indices to recordings from an agricultural landscape in Madagascar. Three acoustic indices showed systematic variation among predominant land-use types. We found a positive correlation of acoustic indices and bird species richness. High indices in structurally diverse vanilla agroforests suggest a high value for conservation. Abstract: New technologies like ecoacoustic surveys promise time and cost efficiency for biodiversity assessments, serve as a basis for effective conservation policies, and are particularly appealing for remote and highly diverse tropical areas. Acoustic indices facilitate the analysis of large acoustic datasets but no consensus on their performance has been reached yet. We evaluated the efficacy of four acoustic indices (Acoustic Complexity Index, Acoustic Diversity Index, Acoustic Evenness Index, Acoustic Entropy) for sound data analysis and biodiversity assessments inside a national park and the agricultural mosaic landscape of north-eastern Madagascar, a global biodiversity hotspot. We used self-built sound recorders to continuously record soundscapes on 80 plots across seven land-use types (old-growth forest, forest fragment, forest–derived and fallow-derived vanilla agroforest, herbaceous and woody fallow, rice paddy) and compared index values between land–use types, assessed the correlation with bird species richness as measured by point counts, and related the acoustic indices to plot- and landscape-scale parameters. The Acoustic Diversity Index, Acoustic Evenness Index (inverse) and Acoustic Entropy were highest in old-growth forest and lowest for rice paddies and fallow land. Index values for structurally similar land-use types did not differ significantly from each other. The correlation of the three acoustic indices with bird species richness was strongest during daytime ( R 2 ≥ 0.30 ) . Differences in the index values were best explained by land-use type and vegetation density. Our results showed that all investigated indices except the Acoustic Complexity Index were suitable biodiversity indicators for a tropical, agricultural landscape. Soundscape diversity was positively affected by plot-scale vegetation structure, emphasizing the importance of forests and particularly old-growth forest for conservation. We demonstrated that acoustic indices and sound recordings are a useful tool for assessing biodiversity in tropical agricultural mosaic landscapes. To realize the full potential of ecoacoustics in conservation, sampling guidelines and user-friendly analysis packages will be key to facilitate a wider implementation.