Recent findings from Queen Mary University of London (QMUL), published in Nature Communications, challenge the prevailing belief regarding climate change and biodiversity.
The research team analyzed an extensive global database of biodiversity surveys spanning marine, freshwater, and terrestrial ecosystems over the last century. Contrary to expectations, they discovered that the rate of species replacement in local habitats, known as "turnover," has not accelerated but rather decreased significantly.
Dr. Emmanuel Nwankwo, the lead author of the study, characterized this phenomenon by stating, "Nature operates like a self-repairing engine, consistently replacing old components with new ones. Our findings indicate that this engine is now experiencing a slowdown."
Global Warming and Declining Species Turnover
The researchers focused on changes occurring since the 1970s, a period marked by a rapid increase in global surface temperatures and more noticeable environmental shifts. They compared species turnover rates before and after this phase of intensified warming.
If climate change were the primary influence, one would expect an increase in turnover rates. However, the analysis revealed a general decline in turnover over short spans of 1-5 years, a trend observed across various ecosystems, from terrestrial bird communities to oceanic life.
Professor Axel Rossberg, a co-author at QMUL, expressed surprise at the strength of the effect, noting that turnover rates typically dropped by one third.
Understanding Internal Ecosystem Dynamics
To comprehend this unexpected outcome, the team delved into the internal organization of ecosystems, moving beyond external climatic factors. Their results suggest that ecological communities do not merely respond to temperature variations; they often function within what is termed the "Multiple Attractors" phase, a concept proposed by theoretical physicist Guy Bunin in 2017.
In this phase, species continuously replace one another due to internal biological interactions, even under stable environmental conditions. This dynamic resembles an ongoing game of rock-paper-scissors, where no single species maintains dominance for extended periods. The new research offers compelling real-world evidence of the existence and significance of this multiple attractors phase in ecosystem dynamics.
Biodiversity Loss and Ecosystem Health
If these internal dynamics typically sustain ecosystem activity, why is turnover declining?
The researchers suggest that environmental degradation and diminishing regional species pools are likely culprits. In a thriving "Multiple Attractors phase" ecosystem, a diverse regional species pool provides a continuous influx of potential newcomers, keeping the cycle of species replacement vibrant.
However, as human activities harm habitats and diminish biodiversity, the number of potential colonizers decreases. With fewer species available for migration, the turnover rate declines.
Dr. Nwankwo remarked, "Our ongoing research indicates that human impacts are contributing to the slowdown of turnover, which is concerning."
The findings imply that ecosystems appearing stable may not be healthy. A reduction in local species turnover could signal a broader depletion of biodiversity, undermining the natural processes that typically maintain ecosystem dynamism and resilience.