This blog post explains a landmark study showing that extreme heat driven by human-caused global warming is the main reason for severe declines in tropical land bird populations. Drawing on global population and climate records, the research quantifies how heat extremes have already reduced tropical bird abundance and highlights worrying examples from the Amazon and Panama, even in largely intact rainforests.
Key findings: heat, not habitat loss, is the biggest driver of tropical bird decline
The study, led by Maximilian Kotz at the Barcelona Supercomputing Center, analyzed bird population trends from 1950 to 2020 and combined those trends with long-term climate records and historical land-use change. The results are stark: heat extremes caused an estimated 25–38% fall in tropical bird abundance over that period.
Some species in places like the Amazon and Panama have declined by as much as 90%, even where forests remain largely undisturbed.
How the researchers reached these conclusions
The team used three major data streams: bird population time series from the Living Planet Database, historical habitat loss metrics from the Hyde Database, and atmospheric and climate datasets from the European Centre for Medium-range Weather Forecasts.
They then applied climate-attribution methods to quantify how much of the intensification of heat extremes is attributable to human-driven global warming, and how much of the observed population decline would not have occurred without that anthropogenic signal.
Why tropical birds are especially vulnerable
Tropical species often live close to their upper thermal limits. That ecological trait makes them disproportionately sensitive to short-lived but severe heat extremes.
Surviving a heatwave is one thing; maintaining condition, avoiding dehydration, and successfully breeding afterward is another.
The study emphasizes that even non-lethal heat exposure can leave birds weakened and reproductively impaired, driving declines over time.
Regional contrasts and the role of habitat loss
While heat extremes are the dominant cause of declines in tropical regions, the analysis confirms that habitat loss remains the primary driver at mid-latitudes.
This geographic contrast underscores that conservation actions must be regionally tailored: protecting and restoring habitat is still vital in temperate zones, while mitigating and adapting to heat exposure is increasingly urgent across the tropics.
The authors also caution that incomplete monitoring in many tropical areas likely means their estimates are conservative.
Data gaps probably mask even greater losses.
Implications for conservation and policy
From three decades working on climate impacts, the implications are clear: addressing this crisis requires simultaneous global and local responses.
Global reductions in greenhouse gas emissions are essential to limit the frequency and intensity of life-threatening heat extremes.
At the same time, targeted conservation measures can help wildlife survive the changes already under way.
Here is the source article for this story: Extreme heat is driving dramatic declines in tropical birds