In the lab, scientists have delivered an eye-popping discovery. It was the fourth confirmation that 2024 will be the hottest year in a century. This year stands out not only for its extreme temperatures but as part of the hottest decade recorded since data collection began. Looking at the past 10 years, the last five rank as some of the hottest in recorded history. This shocking trend begs immediate questions of how it impacts biodiversity and the very real threat to the survival of species around the globe.
Cory Merow and his colleagues at Yale just came out with a game changing study this week published in Proceedings of the National Academy of Sciences. For the first time, they examined the effects of extreme temperatures on more than 33,000 vertebrate species worldwide. To evaluate the impact of treatments, the researchers applied a new bioassessment method developed in 2023. Their goal was to assess the impact of increased heat across various ecosystems and species.
Understanding the Impact of Extreme Heat
The study revealed that the consequences of extreme heat are not random but rather concentrated within specific regions, particularly equatorial South America and Africa. Merow noted, “It seems to be the same species and regions are getting hit during these really hot years and that seems to compound over time, like a bad mortgage. We like to say there’s no rest for the wilted.”
This worrying trend … [is] leading scientists to question whether species have the genetic capacity to keep pace with the unprecedented rate of climate change. Merow further emphasized the difficulty in grasping what these unprecedented extreme temperatures mean for biodiversity. It lets us say, for every species at every point across its range, whether it has been exposed,” he said. Then we sum that across the entire range. In their analysis, they found that half of a species’ range was subject to thermal extremes. On the other hand, they discovered that only 3% experienced these conditions over this time frame.
The researchers underscored that the cascading effects of back-to-back-to-back hottest years can have profound impacts on vulnerable populations. “We don’t know the impacts of the compounding years,” Merow pointed out. Extending the mortgage interest deduction analogy one step further, that’s how demographic shifts happen too. It doesn’t matter how low your interest rate is if your bank account balance hits zero.
The Bioassessment Methodology
Such is the bioassessment method that Merow and his team have recently developed, focusing specifically on species that are most likely to be negatively impacted by climatic extremes. This method offers a more comprehensive view of how specific species are responding to rising temperatures. By measuring exposure levels at various sites, the team of researchers can determine which areas are hot spots and would benefit from interventions.
Merow explained, “We determined the worst a species has seen and then asked whether 2024 was worse, and quite often, it was.” This approach brings to the fore what biodiversity is most urgently threatened. It intends to promote proactive conservation actions for at-risk species.
Urban, the other researcher on this study, stressed the need for targeted assessments. “It’s tricky because all species respond to different things in unique ways,” he stated. “We want a risk assessment that’s both relevant for a wide variety of taxa with different needs but doesn’t require detailed life history knowledge across each species range.”
The Bigger Picture of Climate Change
The inferno of 2024 has ensured that it’s about far more than just specific species. It shines a spotlight on a quickening trend in climate change, one advancing much more quickly than the historical record suggests. Merow expressed concern regarding this rapid change, stating, “That’s what motivates us. 2024 was likely the hottest year in 100,000 years. Species have adapted to recent conditions, and maybe they can survive these novel conditions, or maybe they can’t, but we won’t know without checking in a focused way.”
The urgency for research and understanding continues to grow as scientists work to comprehend the full scope of climate impacts on ecosystems worldwide. These findings from our study underscore the urgent need for us to act now to combat climate change and its impacts on biodiversity.
Urban summarized the situation with a cautionary remark: “A surprising thing is that it’s not simply widespread across tropical locations. We’re not just saying in hot places, things are hot. It’s pretty specific.” This specificity underscores the need for targeted strategies in conservation efforts to mitigate the effects of extreme heat on vulnerable species.