Six out of the last 10 years hold records for being the hottest years measured on earth. We are racing to understand how a temperamental climate will ultimately affect the environment, humans and Earth's rich biodiversity as climate change breathes down our necks. But what part of a changing climate (floods? excess heat? drought?) is the most threatening for species? And can we harness this knowledge to predict the fate of species in the future? Cristian Román-Palacios and John Wiens from the University of Arizona, USA, brought together data from 538 species to take on these weighty questions in a two-part climate change study.
The duo first identified which component of climate change was causing species to disappear and go extinct. They combed through species surveys conducted around the world, taking data from any that measured whether a species (plants and animals) was recorded at a site over at least a 10 year time stretch, allowing them to see which species disappeared over time. They then asked what changes in climate best predicted whether species extinction happened or not. They found that places with the hottest temperatures had more species go extinct – not the hottest average temperature, but the highest temperature peaks. These temperature peaks were three times hotter in places with a species extinction than in places without an extinction. While other aspects of climate change were also related to species disappearances, temperature spikes were the most important driver.
Equipped with that knowledge, Román-Palacios and Wiens turned their gaze to the future. They used climate models to estimate whether a species would go extinct in its habitat over the next 50 years given the temperature peaks they would experience. They did this under two climate scenarios: one where we curb our greenhouse gas emissions (the ‘best-case scenario’) and one where greenhouse gas emissions continue to skyrocket unchecked (the ‘worst-case scenario’). Depressingly, 78% (best case) to 86% (worst-case) of the 538 species will go extinct by 2070 if they stay in their present-day habitats. But plants and animals aren't fettered to one place. Species can persist by either moving and tracking their habitat across a changing landscape (yes, even plants can do this) or adapting to the new climate. The team used the historical survey data to estimate how far each species could move and their ability to adapt and survive in different future climates. When the researchers factored in species movement, 57–70% would still go extinct; however, when they considered their ability to adapt, the percentage extinctions fell to 35–42%.
Román-Palacios and Wiens’ work truly advances our understanding of climate change in two important ways. First, they show that we should pay attention to heat peaks, not just rising temperature averages. Second, they show that a species’ ability to adapt to climate change may be more important for their survival than their ability to move. The pair's findings promisingly show that if we stick to the Paris Agreement's effort to limit the temperature increase to 1.5°C, we should see the best-case scenario play out in real life over the next 50 years.