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 extensive 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/elevational gradients in the rainforest of the Australian Wet Tropics World Heritage Area to assess changes in local abundance and elevational distribution. We used relative abundance 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 species. 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 Australian 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 tropical montane ecosystems globally.
Highlights
There is widespread recognition that climate change is rapidly becoming the most significant threat to global biodiversity and natural ecosystems [1,2]
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 [5,6,7]
Across all 42 species over the 17 years, there has been a significant decline in local abundance of rainforest birds of approximately 12 ± 1.4% (~ -0.2% per year) (Fig 1A and Table 1)
Summary
There is widespread recognition that climate change is rapidly becoming the most significant threat to global biodiversity and natural ecosystems [1,2]. Estimates of total species extinctions projected over the remainder of the century vary considerably between ecosystems, taxa and methods of analysis [3]. 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 [5,6,7].
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