The projected timing of abrupt ecological disruption from climate change

The projected timing of abrupt ecological disruption from climate change

Christopher H. Trisos, Cory Merow & Alex L. Pigot

Summarized by Shaina Sadai

What data were used? The data used is a combination of climate model output and ecological data for 30,652 marine and terrestrial species. For each species they determine the climate conditions and spatial extents that a species is known to have existed in throughout history. The climate model output that was used were temperature and precipitation data from 22 different models and 3 emissions scenarios (RCP2.6, 4.5, 8.5).

Methods: The authors created species assemblages contained in 100km^2 grid cells. Using these they generated ‘horizon profiles’ which give the percentage species within each assemblage that would experience climate conditions exceeding those of their historic limits at a given time. They cross referenced when each species would be living for more than 5 years straight in an area where the temperature exceeded the maximum temperature they have been known to exist at through their history in order to quantify when a species crossed their ecological limit. By repeating this method across the planet they were able to construct horizon profiles at many locations, including sensitive ecosystems such as the Amazon Basin and Gobi Desert.

Results: One of the most striking results is how abrupt impacts to biodiversity could be. The profiles show that an average of over 70% of species in a given assemblage were exposed to conditions exceeding their limits within a single decade, regardless of climate model of emissions scenario. This was in part due to the species within a region evolving for similar temperature ranges. The abruptness of when ecological limits were breached was even higher for marine ecosystems than terrestrial ones. Tropical species are particularly vulnerable to having a higher percentage of species exposed to dangerous temperatures by the end of the century because they already exist in places where they are close to their temperature limits. Polar species were also highly vulnerable due to the rapid rate of changes occurring in these regions.

Under higher emissions scenarios (RCP8.5) temperature thresholds are exceeded sooner with some occurring even before 2030. The most vulnerable regions were the Amazon, Indian subcontinent, and Indo-Pacific regions where by 2100 over 90% of species in any assemblage were exposed to temperatures over their limits. In contrast the low emissions scenario (RCP2.6) delays the point at which vulnerable species are at risk by 60 years. If warming by the end of the century is kept below 2C only 2% of species assemblages will be exposed to abrupt exposure events.

Why is this study important? This study was able to use a combination of data on species’ ecological limits and climate model data to give a robust picture of when and where species assemblages may cross safe limits. It shows the potential for abrupt loss, particularly of biodiverse ecosystems, and can help inform policy efforts and future research needed to assess risk.  If emissions are decreased and the rate of temperature increase is slower it gives species more time to adapt.

The big picture: We must prepare for significant impacts to ecosystems and biodiversity under a changing climate, and take steps to prevent serious ecological harm. Yet again we see that early mitigation is crucial to mitigate harm.

Trisos, C.H., Merow, C. & Pigot, A.L. The projected timing of abrupt ecological disruption from climate change. Nature 580, 496–501 (2020).

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