Acoustic indices applied to biodiversity monitoring in a Costa Rica dry tropical forest

Izaguirre, Mónica Isabel Retamosa; Ramírez-Alán, Óscar

doi:10.22261/jea.tnw2np

Cited by 29 publications

(13 citation statements)

References 48 publications

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“…4C ). Most studies tested more than one acoustic index (53%; Mammides et al ., 2017 ; Retamosa Izaguirre & Ramírez‐Alán, 2018 ; Eldridge et al ., 2018 ) and estimated diversity metrics from acoustic sources (68%). Over the environments and organisms investigated, research has mainly focused on terrestrial habitats (71%), birds (54%; Fig.…”

Section: Resultsmentioning

confidence: 99%

Acoustic indices as proxies for biodiversity: a meta‐analysis

et al. 2022

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As biodiversity decreases worldwide, the development of effective techniques to track changes in ecological communities becomes an urgent challenge. Together with other emerging methods in ecology, acoustic indices are increasingly being used as novel tools for rapid biodiversity assessment. These indices are based on mathematical formulae that summarise the acoustic features of audio samples, with the aim of extracting meaningful ecological information from soundscapes. However, the application of this automated method has revealed conflicting results across the literature, with conceptual and empirical controversies regarding its primary assumption: a correlation between acoustic and biological diversity. After more than a decade of research, we still lack a statistically informed synthesis of the power of acoustic indices that elucidates whether they effectively function as proxies for biological diversity. Here, we reviewed studies testing the relationship between diversity metrics (species abundance, species richness, species diversity, abundance of sounds, and diversity of sounds) and the 11 most commonly used acoustic indices. From 34 studies, we extracted 364 effect sizes that quantified the magnitude of the direct link between acoustic and biological estimates and conducted a meta-analysis. Overall, acoustic indices had a moderate positive relationship with the diversity metrics (r = 0.33, CI [0.23, 0.43]), and showed an inconsistent performance, with highly variable effect sizes both within and among studies. Over time, studies have been increasingly disregarding the validation of the acoustic estimates and those examining this link have been progressively reporting smaller effect sizes. Some of the studied indices [acoustic entropy index (H), normalised difference soundscape index (NDSI), and acoustic complexity index (ACI)] performed better in retrieving biological information, with abundance of sounds (number of sounds from identified or unidentified species) being the best estimated diversity facet of local communities. We found no effect of the type of monitored environment (terrestrial versus aquatic) and the procedure for extracting biological information (acoustic versus non-acoustic) on the performance of acoustic indices, suggesting certain potential to generalise their application across research contexts. We also identified common statistical issues and knowledge gaps that remain to be addressed in future research, such as a high rate of pseudoreplication and multiple unexplored combinations of metrics, taxa, and regions. Our findings confirm the limitations of acoustic indices to efficiently quantify alpha biodiversity and highlight that caution is necessary when using them as surrogates of diversity metrics, especially if employed as single predictors. Although these tools are able partially to capture changes in diversity metrics, endorsing to some extent the rationale behind acoustic indices and suggesting them as promising bases for future developments, they are far from being direct pr...

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Section: Resultsmentioning

confidence: 99%

Acoustic indices as proxies for biodiversity: a meta‐analysis

et al. 2022

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“…According to research results, the use of a single index does not always allow the relationship between its value and the species richness of birds. Therefore, some researchers have proposed the use of combinations of indices (Towsey et al, 2014;Retamosa Izaguirre et al, 2018). The integration of several acoustic parameters allowed to characterize and identify habitats with varying degrees of disturbance (mature forest, secondary growth and pasture) in Colombia (Gόmez et al, 2018) accurately predicted the diversity of birds in India (Buxton et al, 2018), etc.…”

Section: Discussionmentioning

confidence: 99%

Impact of stand variables on characteristics of avian soundscape in common oak (Quercus robur L.) forests

Atemasov

Atemasova

2019

Forestry Studies

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One of the problems that may arise when conducting long-term monitoring of bird populations in forest landscapes may be discrepancies between data obtained by different researchers. Using acoustic monitoring may solve this problem. To establish the suitability of the acoustic method for monitoring the state of forest ecosystems, studies were conducted in May and June 2018 on seven plots different from each other by stand age and species composition in a maple-linden-oak forest in northeastern Ukraine. The species composition of birds, the structure and composition of the stand and the values of six acoustic indices were calculated. Differences were found in all acoustic indices at different sites. The smallest values of the indices were noted in the overgrown clear-cut. Four acoustic indices in the May survey and five of the six in the June survey show significant correlations with the species richness of birds. All indices correlate with the values of several stand variables, which characterize the size and species composition of the stand, understorey and field vegetation, the closeness of various vegetation tiers, and with the distance to the edges and the nearest populated areas. The results suggest the possibility of using an acoustic approach to monitoring the bird population and the state of forest ecosystems.

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“…ACI has shown mixed results regarding its ability as a bird indicator. Some studies found positive relationships between ACI and number of bird vocalizations (Pieretti et al, 2011), species richness and bird abundance (Eldridge et al, 2018;Retamosa et al, 2018), or bioacoustic activity in general (Towsey et al, 2014). Other studies found weak or negative relationships between ACI and species richness or biophonic activity (Mammides et al, 2017;Eldridge et al, 2018).…”

Section: Discussionmentioning

confidence: 99%

“…amplified redundancy or song intensity) to offset noise masking effect. On the other hand, BIO has been tested in different environments, showing positive correlation with bird richness (Eldrigde et al, 2018), abundance (Retamosa et al, 2018), number of vocalizations (Pieretti et al, 2011) and biotic diversity (Fairbrass et al, 2017).…”

Section: Discussionmentioning

confidence: 99%

Vegetation, bird and soundscape characterization: a case study in Braulio Carrillo National Park, Costa Rica

Izaguirre

Sequeira

Barrantes-Madrigal

et al. 2021

Biota

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We assessed the structural complexity of vegetation, birds and soundscapes in two areas of Braulio Carrillo National Park, Costa Rica, with different road exposure, as baseline information for conservation and management. We measured vegetation structure complexity, surveyed birds and recorded soundscapes in an area adjacent to the National Highway 32 (Quebrada) and another area 20 km away (Ceibo). Quebrada presented a more open forest structure and lower density of trees and shrubs; lower evenness and higher acoustic complexity, higher bioacoustic activity and sound pressure level; higher bird abundance and richness. Ceibo showed a higher density of trees and shrubs, higher complexity of vegetation structure, higher proportion of biophonies than anthrophonies, and an acoustic community with higher diversity and entropy. The study sites differed in characteristics of their bird communities in an unexpected way; these differences appear to be mostly influenced by the structure and complexity of the vegetation surrounding the road. However, the soundscapes seemed to properly reflect the habitat condition, and are promising for evaluating the ecological condition of a site.

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Acoustic indices applied to biodiversity monitoring in a Costa Rica dry tropical forest

Cited by 29 publications

References 48 publications

Acoustic indices as proxies for biodiversity: a meta‐analysis

Acoustic indices as proxies for biodiversity: a meta‐analysis

Impact of stand variables on characteristics of avian soundscape in common oak (Quercus robur L.) forests

Vegetation, bird and soundscape characterization: a case study in Braulio Carrillo National Park, Costa Rica

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