Focus on poleward shifts in species’ distribution underestimates the fingerprint of climate change

Species are largely predicted to shift poleward as global temperatures increase, with this fingerprint of climate change being already observed across a range of taxonomic groups and, mostly temperate, geographic locations1–5. However, the assumption of uni-directional distribution shifts does not account for complex interactions among temperature, precipitation and species-specific tolerances6, all of which shape the direction and magnitude of changes in a species’ climatic niche. We analysed 60 years of past climate change on the Australian continent, assessing the velocity of changes in temperature and precipitation, as well as changes in climatic niche space for 464 Australian birds. We show large magnitude and rapid rates of change in Australian climate over the past 60 years resulting in high-velocity and multi-directional, including equatorial, shifts in suitable climatic space for birds (ranging from 0.1 to 7.6 km yr−1, mean 1.27 km yr−1). Overall, if measured only in terms of poleward distribution shifts, the fingerprint of climate change is underestimated by an average of 26% in temperate regions of the continent and by an average of 95% in tropical regions. We suggest that the velocity of movement required by Australian species to track their climatic niche may be much faster than previously thought and that the interaction between temperature and precipitation changes will result in multi-directional distribution shifts globally. The future velocity of climate change is expected to be high7, largely outpacing the potential of species to adapt8,9, and as such, distributional shifts are considered the most likely species response. There is increasing evidence that changing climates of the past century have already resulted in a globally consistent fingerprint of poleward or rising elevation shifts in species distributions2–4,6,10. For example, a recent meta-analysis reported that the distributions of species across a wide range of taxonomic groups and geographic locations have shifted to higher latitudes at a median rate of 1.69 km yr−1, and to higher elevations at a median rate of 1.1m yr−1 (ref. 4). The authors conclude that the velocity of distribution shifts generally matches that expected on the basis of average temperature change in the regions of study, but note the high levels of variation in response within taxonomic groups. The expectation that species will shift poleward or upward is based on analyses using a relatively certain and easily understood metric of climate change—global temperature—which is broadly correlatedwith latitude and elevation. Changes in precipitationwith global warming are much more difficult to predict and are more likely to be regionally specific11,12. In addition, species biological responses to temperature are often better understood than they are for precipitation and therefore precipitation has often been omitted