The impact of climate change changes over time

- We model the potential distribution of 15 invasive ants in 2020, 2050 and 2080.
- For 6 species modelled, the trend in climate change impacts changed over time.
- A range expansion was followed by a contraction over time, or vice versa.
- In one species, an expansion of 36.5% was followed by a decrease of 64.3%.
- Management decisions would be misled if based on a single time horizon.

Species distribution models (SDMs) have become an important tool to predict the impact of climate change on the distribution of a given species. Generally, projections for a chosen time horizon in the future are compared with the size of the species' current distribution. In this study, we show that selection of the target time horizon can qualitatively alter the prediction of a species' future distribution. We illustrate this by assessing the potential distribution of 15 invasive ant species in 2020, 2050 and 2080 at a global scale. Our results indicate that for 6 out of the 15 species modelled, the trend of potential habitat size (i.e., decrease or increase) changed over time following climate change. In four species, the sign of the trend changed, from an initial expansion to a subsequent reduction or vice versa, depending on the date projected to. In some cases, these changes were great (e.g., from an initial increase of 36.5% in 2050 to a decrease of −64.3% in 2080). Our findings stress the importance of using several projection horizons to avoid misled species management decisions.