Recent ecological responses to climate change support predictions of high extinction risk

Abstract

Predicted effects of climate change include high extinction risk for many species, but confidence in these predictions is undermined by a perceived lack of empirical support. Many studies have now documented ecological responses to recent climate change, providing the opportunity to test whether the magnitude and nature of recent responses match predictions. Here, we perform a global and multitaxon metaanalysis to show that empirical evidence for the realized effects of climate change supports predictions of future extinction risk. We use International Union for Conservation of Nature (IUCN) Red List criteria as a common scale to estimate extinction risks from a wide range of climate impacts, ecological responses, and methods of analysis, and we compare predictions with observations. Mean extinction probability across studies making predictions of the future effects of climate change was 7% by 2100 compared with 15% based on observed responses. After taking account of possible bias in the type of climate change impact analyzed and the parts of the world and taxa studied, there was less discrepancy between the two approaches: predictions suggested a mean extinction probability of 10% across taxa and regions, whereas empirical evidence gave a mean probability of 14%. As well as mean overall extinction probability, observations also supported predictions in terms of variability in extinction risk and the relative risk associated with broad taxonomic groups and geographic regions. These results suggest that predictions are robust to methodological assumptions and provide strong empirical support for the assertion that anthropogenic climate change is now a major threat to global biodiversity.

Fig. 1.

Proportion of taxa subject to varying degrees of extinction risk by 2100. Actual proportion derived from studies (histogram bars) together with a fitted β-probability function (black curve). The horizontal hatched bars (actual) and horizontal black lines (modeled) represent the number of studies with an extinction risk of zero or one. (A and B) Uncorrected estimates derived from observed (A) and predicted (B) data. (C and D) Estimates accounting for biases (Methods) derived from observed (C) and predicted (D) data. (E and F) Modeled probability density functions (green, observed; orange, predicted) overlaid to show that, when uncorrected (E), the variance in extinction risk derived from observed and predicted data is similar, and when corrected (F), the means are similar.

Fig. 2.

Frequency distribution of extinction risk by 2100 in (Left) observed and (Right) predicted studies of taxa: (Top Left and Top Right) plants, (Middle Left and Middle Right) invertebrates, and (Bottom Left and Bottom Right) vertebrates. Actual proportion derived from studies (histogram bars) together with a fitted β-probability function (black curve). The dark bars (actual) and horizontal black lines (modeled) represent the frequency of studies with an extinction risk of zero or one. Data are scaled such that the total area of histogram bars and under the modeled extinction risk line is equal to one. N is the number of samples in each category.

Fig. 3.

Frequency distribution of extinction risk by 2100 in (Left) observed and (Right) predicted studies of ecoregions: (row 1) polar and boreal, (row 2) temperate, (row 3) tropical and subtropical, and (row 4) marine. Actual proportion derived from studies (histogram bars) together with a fitted β-probability function (black curve). The dark bars (actual) and horizontal black lines (modeled) represent the frequency of studies with an extinction risk of zero or one. Data are scaled such that the total area of histogram bars and under the modeled extinction risk line is equal to one. N is the number of samples in each category.