A TALE OF TWO CLIMATES: PREDICTING SPECIES' RESPONSES TO CHANGING ENVIRONMENTS THROUGH TIME

Many investigations of the fossil record have revealed that processes operating on short time scales may not fully explain patterns observed over longer time periods. This illustrates the perils of using uniformitarian approaches to extrapolate patterns backwards or forwards in time. The issue of extrapolation is important because biologists and paleontologists alike are concerned about how accelerating climate change will impact biodiversity. One important factor that makes extrapolation through time difficult is the existence of distinct, or non-analogous, climatic or ecological conditions relative to a given reference point. Ecological niche modeling (ENM) is one of the primary quantitative tools used to investigate and predict how climate change will and has influenced biogeographic distributions and could potentially trigger extinction. ENM is a computer-algorithm-based approach that uses environmental parameters and species’ occurrence points to build a multi-dimensional prediction of the abiotic conditions suitable for a species. Model results can then be projected onto future (or other distinct) climate scenarios to glean how a given species may respond to differing conditions.

Non-analogous climatic conditions pose a unique set of challenges for applying ENM and predicting species’ responses to environmental change. Mechanistically, algorithms encountering unique environmental conditions may extrapolate suitability in unpredictable ways. We present a new analysis tool, mobility-oriented parity (MOP), which provides a metric to assess similarity between model-trained and projection environments and highlight non-analogous regions. This is especially important in quantifying where and when ecological data can and cannot be applied to consider longer-term patterns of change. In this regard, the adage of “the past is the key to the present” holds particular relevance. The fossil record provides direct evidence of how species responded to non-analogous climatic conditions through time. We will describe how this can be assessed using ENM in conjunction with MOP, thereby testing assumptions of uniformitarianism. This will have broad implications for how biologists of all stripes interpret their models and enact conservation policy.