Biodiversity patterns change predictably with scale across ecosystems

The number of species does not rise at a constant rate as the scope of study expands from small local areas to entire continents. This uneven scaling of biodiversity, recognized for decades, now has a theoretical explanation thanks to an international team led by scientists from the German Centre for Integrative Biodiversity Research (iDiv) and Martin Luther University Halle-Wittenberg (MLU). Their findings, published in Nature Communications, reveal a new model that characterizes how species counts increase in three distinct phases as geographic area expands.

Species diversity, known to increase with area, displays what ecologists term Species-Area Relationships (SARs). The new model identifies three SAR phases: a rapid species gain from local to regional scales, a slower increase from regional to continental scales, and another acceleration at continental to intercontinental levels. This pattern reflects how species' geographical ranges overlap and disperse.

Lead author Dr Luis Borda-de-Agua from CIBIO in Portugal notes, "We demonstrated that the individual geographical ranges of all species within the studied areas shape the typical species distribution patterns (SARs) we observe across the globe. By combining these distributions in a novel way, we developed a formula to estimate the number of species at the transitions between different phases."

This new predictive capability holds vital implications for conservation. It can help pinpoint where the rate of species emergence changes and assess biodiversity losses tied to habitat destruction. These transition points also provide critical data for estimating extinction rates used in global biodiversity assessments.

The researchers validated their model by analyzing SARs across birds, amphibians, and other taxa, using a dataset of approximately 700 million individual species observations. The model's predictions closely aligned with observed data, reinforcing its robustness.

Senior author Prof Henrique Pereira from iDiv and MLU adds, "New findings like ours unveil hidden patterns that have been shaping life on Earth for millions of years. Just as physics deciphers the universe's deepest mysteries, new ecological theory can reveal the fundamental forces shaping biodiversity on our amazing planet."

Research Report:Modelling the species-area relationship usingextreme value theory