Safety margins for climate warming in a continental flora

Rachael Gallagher (1), Ian J. Wright (1), Mark Westoby (1)

1 Department of Biological Sciences, Macquarie University, North Ryde, NSW 2109, @ecolo_gist

How resilient are current communities to climate warming? We approach this fundamental question in global change biology using data for the entire higher-plant flora of Australia and a novel niche turnover metric – the ‘safety-margin for climate warming’. Point occurrence data from herbarium specimens for 19,227  plant  species  were  cleaned  and intersected with current  climatologies  to estimate  the  upper, realised niche limit for each species. In each location (0.5º grid cell), we calculated a frequency distribution of differences in location temperature and the upper niche limit of each species present and mapped the mean. This metric shows how much warmer conditions can become before a typical species in a location would need to  be  replaced via turn-over. Estimating the rate of niche turnover in this way explicitly measures the safety-margin for climate warming in each landscape location, in terms of the average niche limits of the current community. Mapped patterns were compared among different plant functional types and spatially-explicit models were used to test for associations between safety-margin, range size, latitude, and  abiotic conditions  (e.g.  topography,  soils).  Across the  Australian landscape,  the safety margin for climate  warming  in  higher-plant  communities  varied  between  0.1-8.1ºC.  The  smallest  margins  were confined to equatorial regions and topography was a key predictor of variation. Alpine locations had consistently higher safety margins, suggesting that mountainous zones may be more resilient to direct climate warming than previously thought.

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