Biodiversity assessment remains one of the most difficult challenges encountered by ecologists and conservation biologists.\r\nThis task is becoming even more urgent with the current increase of habitat loss. Many methodsââ?¬â??from rapid biodiversity\r\nassessments (RBA) to all-taxa biodiversity inventories (ATBI)ââ?¬â??have been developed for decades to estimate local species\r\nrichness. However, these methods are costly and invasive. Several animalsââ?¬â??birds, mammals, amphibians, fishes and\r\narthropodsââ?¬â??produce sounds when moving, communicating or sensing their environment. Here we propose a new concept\r\nand method to describe biodiversity. We suggest to forego species or morphospecies identification used by ATBI and RBA\r\nrespectively but rather to tackle the problem at another evolutionary unit, the community level. We also propose that a part\r\nof diversity can be estimated and compared through a rapid acoustic analysis of the sound produced by animal\r\ncommunities. We produced a and b diversity indexes that we first tested with 540 simulated acoustic communities. The a\r\nindex, which measures acoustic entropy, shows a logarithmic correlation with the number of species within the acoustic\r\ncommunity. The b index, which estimates both temporal and spectral dissimilarities, is linearly linked to the number of\r\nunshared species between acoustic communities. We then applied both indexes to two closely spaced Tanzanian dry\r\nlowland coastal forests. Indexes reveal for this small sample a lower acoustic diversity for the most disturbed forest and\r\nacoustic dissimilarities between the two forests suggest that degradation could have significantly decreased and modified\r\ncommunity composition. Our results demonstrate for the first time that an indicator of biological diversity can be reliably\r\nobtained in a non-invasive way and with a limited sampling effort. This new approach may facilitate the appraisal of animal\r\ndiversity at large spatial and temporal scales.
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