Long-term changes in populations of rainforest birds in the Australia Wet Tropics bioregion: A climate-driven biodiversity emergency

RESEARCH ARTICLE Long-term changes in populations of rainforest birds in the Australia Wet Tropics bioregion: A climate-driven biodiversity emergency Stephen E. WilliamsID*, Alejandro de la Fuente Centre for Tropical Environmental Science & Sustainability, College of Science and Engineering, James Cook University, Townsville, Australia * Stephen.williams@jcu.edu.au Abstract Many authors have suggested that the vulnerability of montane biodiversity to climate change worldwide is significantly higher than in most other ecosystems. Despite the exten- sive variety of studies predicting severe impacts of climate change globally, few studies have empirically validated the predicted changes in distribution and population density. Here, we used 17 years (2000–2016) of standardised bird monitoring across latitudinal/ele- vational gradients in the rainforest of the Australian Wet Tropics World Heritage Area to assess changes in local abundance and elevational distribution. We used relative abun- dance in 1977 surveys across 114 sites ranging from 0-1500m above sea level and utilised a trend analysis approach (TRIM) to investigate elevational shifts in abundance of 42 spe- cies. The local abundance of most mid and high elevation species has declined at the lower edges of their distribution by >40% while lowland species increased by up to 190% into higher elevation areas. Upland-specialised species and regional endemics have undergone dramatic population declines of almost 50%. The “Outstanding Universal Value” of the Aus-

tralian Wet Tropics World Heritage Area, one of the most irreplaceable biodiversity hotspots on Earth, is rapidly degrading. These observed impacts are likely to be similar in many tropi- cal montane ecosystems globally. Introduction There is widespread recognition that climate change is rapidly becoming the most significant threat to global biodiversity and natural ecosystems [1,2]. At a global scale, estimates of total species extinctions projected over the remainder of the century vary considerably between eco- systems, taxa and methods of analysis [3]. However, in all studies, the level of predicted impacts is disturbing with potential losses of between 15–35% of all species [3,4]. The projected impact of climate change is expected to be especially severe in mountain ecosystems with up to 84% of mountain species globally facing a high extinction risk [5–7]. Mountain regions PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.0254307 December 22, 2021 1 / 16 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Williams SE, de la Fuente A (2021) Long- term changes in populations of rainforest birds in the Australia Wet Tropics bioregion: A climate- driven biodiversity emergency. PLoS ONE 16(12): e0254307. https://doi.org/10.1371/journal. pone.0254307 Editor: Angelina Martı´nez-Yrı´zar, UNAM, MEXICO Received: June 15, 2021 Accepted: November 5, 2021 Published: December 22, 2021 Copyright: © 2021 Williams, Fuente. This is an open access article distributed under the terms of the Creative Commons Attribution License, which

permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: The raw data (attached as the excel file) and a link to the full interactive appendix can be found here: https://doi. org/10.25903/3tmd-sw18. Funding: All SEW and many grants over the long term study - principal funding organisations listed below: Earthwatch Institute; James Cook University; Australian Research Council; Australian Government - Department of Environment. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.