The world is undergoing its sixth major extinction crisis, and as many reports have shown, our warming planet puts many more species at risk of annihilation. A new study published in Nature on Wednesday takes an even deeper look at the crisis and what ecosystem-wide changes could look like.
They doesn’t look good. Biodiversity loss is like a game of Jenga—if the world crosses certain temperature thresholds and enough species in an ecosystem die out, the whole structure can collapse. The authors found that due to the climate crisis, ecosystems could abruptly cross those thresholds in a matter of years.
Using climate data from 1850 to 2005, the authors identified the warmest average annual temperatures that 30,652 species—including birds, mammals, reptiles, amphibians, fish, and plants—have ever withstood. They then studied climate projections up to the year 2100 to predict when species may experience temperatures beyond these limits.
The approach differs from previous reports that either show only the trajectories of individual species over time, or focus on snapshots which illustrate how many species we’ll lose by a specific point in the future. The findings show that many species within specific ecosystems will be subject to unprecedented temperatures at the same time, creating an “abrupt” disruption that could upend ecosystems completely.
“Within a certain area, most species for a while will be living within conditions they have previously experienced somewhere in their range, and thus where we have good evidence that they can survive,” Alex Pigot, the study’s lead author and research fellow at the University College London, told Earther in an email. “However… once temperatures rise to levels a species has never experienced, scientists have very limited evidence of their ability to survive.”
If emissions continue to rise and the planet continues to warm, tropical oceans could reach temperature thresholds that cause ecosystem-wide collapse as early as 2030. And there are signs damage is already being done due to the roughly 1 degree Celsius (1.8 degrees Fahrenheit) of heating the world has experienced since the start of the Industrial Revolution.
“Our study suggests that exposure of species to potentially dangerous temperatures is already underway in the tropical oceans a finding consistent with the mass bleaching of coral reefs that we are now seeing on an almost yearly basis such as on the Great Barrier Reef,” said Pigot.
Indeed, a study released this week detailed an unprecedented mass bleaching event in the reef happening right now. Though ecosystems in tropical forests and higher latitude regions will generally be capable of withstanding higher temperatures, the new Nature study shows those areas could see similar effects by 2050.
But if the world get on track to limit global warming to 2 degrees Celsius (3.6 degrees Fahrenheit) above preindustrial temperatures, much of that devastation could be prevented. Less than 2 per cent of ecosystems globally would undergo these abrupt, system-wide shifts, defined as losing 20 per cent or more of their constituent species.
“By holding warming below 2 degrees Celsius, we can effectively ‘flatten the curve’ of how climate risks to biodiversity accumulates over time, delaying the exposure of the most at risk species by many decades and averting exposure entirely for many thousands of species,” said Pigot.