Below the canopy: global trends in forest vertebrate populations and their drivers
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Abstract
Global forest assessments use forest area as a proxy indicator of biodiversity status, which may mask below-canopy pressures driving forest biodiversity loss and ‘empty forest’ syndrome. The status of forest biodiversity is important not only for species conservation but also because species loss can have consequences for forest health and carbon storage. We aimed to develop a global indicator of forest specialist vertebrate populations to improve assessments of forest biodiversity status. For this purpose we used the Living Planet Index methodology, developing a weighted composite Forest Specialist Index for the period 1970-2014. We then investigated potential drivers of forest vertebrate population change, including tree cover change, to determine whether forest area is a good proxy for forest biodiversity. The effects of satellite-derived tree cover trends and other pressures on the average rate of change of forest vertebrate populations were analysed. We reviewed the literature to gain more context-specific information relating to drivers of forest specialist population change. On average, forest vertebrate populations declined by 53% between 1970 and 2014. We found little evidence of a consistent global effect of tree cover change on forest vertebrate populations but a significant negative effect of exploitation threat on forest specialists. However, time-series cross-correlation analyses showed some forest specialist populations are closely aligned to tree cover change. The literature review identified several drivers of population change that cannot be detected remotely and may cause populations to change independently of tree cover. Forest vertebrate populations have more than halved since the 1970s. In conclusion, we found that forest area is a poor proxy of forest biodiversity status. For forest biodiversity to recover, we must monitor and manage all threats to vertebrates, including those below the canopy.
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2019. Below the canopy: global trends in forest vertebrate populations and their drivers. PeerJ Preprints 7:e27882v1 https://doi.org/10.7287/peerj.preprints.27882v1Author comment
This is a preprint submission to PeerJ Preprints.
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Competing Interests
The authors declare that they have no competing interests.
Author Contributions
Elizabeth J. Green conceived and designed the experiments, analyzed the data, contributed reagents/materials/analysis tools, prepared figures and/or tables, authored or reviewed drafts of the paper, approved the final draft.
Louise McRae conceived and designed the experiments, analyzed the data, contributed reagents/materials/analysis tools, prepared figures and/or tables, authored or reviewed drafts of the paper, approved the final draft.
Robin Freeman conceived and designed the experiments, contributed reagents/materials/analysis tools, authored or reviewed drafts of the paper, approved the final draft.
Mike B.J. Harfoot conceived and designed the experiments, contributed reagents/materials/analysis tools, authored or reviewed drafts of the paper, approved the final draft.
Samantha L.L. Hill conceived and designed the experiments, authored or reviewed drafts of the paper, approved the final draft.
William Baldwin-Cantello conceived and designed the experiments, authored or reviewed drafts of the paper, approved the final draft.
William D. Simonson conceived and designed the experiments, authored or reviewed drafts of the paper, approved the final draft.
Data Deposition
The following information was supplied regarding data availability:
The vertebrate population data was taken from the Living Planet Database which is hosted online at www.livingplanetindex.org. The data are freely available with the exception of 439 time-series which have been shared confidentially and cannot be viewed or downloaded. The Forest Specialist Index was calculated using the R package rlpi available at https://github.com/Zoological-Society-of-London/rlpi.
Funding
This work was funded and supported by WWF-UK, WWF-Germany and WWF-France. Institutional support was also provided by ZSL Institute of Zoology. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
