July 30: Human induced climate change could transform tropical vegetation by 2050 on a scale comparable to 3.3 million years of natural ecological change, according to a new study published in the Journal of Biogeography.
Researchers from the Remote Sensing Center at the Federal University of Minas Gerais (UFMG), Brazil, reconstructed the distribution of tropical forests, savannas and deserts over the past 3.3 million years using satellite data, paleoclimate records and machine learning. They then projected how these ecosystems may change under future climate scenarios.
The study found that tropical ecosystems have historically changed gradually over hundreds of thousands to millions of years, allowing species time to migrate, adapt and evolve. However, projected climate change could compress transformations of similar magnitude into just a few decades, leaving many species unable to cope.
Around 3.2 million years ago, when global temperatures were nearly 4°C warmer than today, tropical forests reached their smallest recorded extent. The Amazon rainforest covered less than half of its current area, while the Atlantic Forest shrank to less than five per cent of its potential extent. Savannas replaced many areas now occupied by dense forests.
The research also identified long-term climate refuges. About 22 per cent of the tropical region remained climatically stable throughout the past 3.3 million years, allowing biodiversity to accumulate over time. Nearly one third of the Malay Archipelago retained continuous forest cover during this period, making it the most stable tropical region on Earth.
Under the highest greenhouse gas emissions scenario, temperatures across the tropics could rise by 2°C to 4°C by 2050, with parts of the Amazon warming by as much as 4°C. Researchers warn that rising temperatures and prolonged drought could convert dense rainforest into more open vegetation, causing the Amazon to lose more than one third of its forests.
The Malay Archipelago, which has remained largely stable for millions of years, could also lose more than 40 per cent of its forest cover. Scientists caution that ecosystems and species adapted to long term environmental stability may be especially vulnerable to such rapid climate shifts.
The researchers conclude that while natural climate changes have previously contributed to extinctions over long timescales, the accelerated pace of human driven climate change could pose far greater risks to tropical biodiversity and ecosystem resilience.