Several bird populations have seen declines of up to 90% in tropical regions like the Amazon and Panama, even in areas of the rainforest that remain largely untouched . Current research indicates that extreme heat is likely the primary factor driving these declines.

From 1950 to 2020, intense heatwaves led to a 25-38% decrease in bird populations inhabiting these biodiverse tropical regions, as reported by Maximilian Cotts and his team from Barcelona’s Super Computing Center.

The researchers have yet to utilize these findings to forecast future bird population trends as global temperatures continue to rise, but early indicators are concerning. “The situation looks grim,” Cotts remarks.

He and his team have initiated a comprehensive analysis of global bird populations using the Living Planet Database. This dataset, however, does not include seabirds. Additional data on habitat destruction was sourced from the Hyde database for global environments, along with historical weather and climate data from the European Centre for Medium-Range Weather Forecasts.

The researchers compared this information to identify correlations that could shed light on the observed changes in bird populations. Their findings suggest that habitat loss is a significant driver of decline, corroborating earlier studies, particularly in regions with latitudes between 21° and 43° north or south.

In contrast, extreme heat is the predominant factor affecting bird survival in tropical areas, where many species often exist at the edge of their heat tolerance limits. If these limits are exceeded, they risk mortality , explains Kotz. Even if they manage to survive an intense heat episode, their health is typically compromised, diminishing their reproductive success.

The team is also analyzing how the exacerbation of extreme heat is attributable to anthropogenic climate change, and how bird populations would behave in a scenario without warming. This approach enables researchers to gauge the impact of climate change on bird abundance.

Although such attribution studies have been traditionally employed to assess extreme weather events related to climate change, Kotz notes that this is the first instance of applying this methodology to evaluate ecological repercussions.

There remains a significant lack of data regarding bird population trends, particularly in tropical regions. Kotz acknowledges this deficiency but believes there is enough evidence to draw meaningful conclusions. He cautions that insufficient data in these areas may lead to an underestimation of the impacts.

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