A comprehensive global analysis of thousands of animal and plant species has unveiled a concerning trend of species shrinking, with a notable impact on fish sizes. Researchers have observed changes in the body size of various species, most prominently in fish populations. The study, conducted by an international team of scientists from 17 universities, compiled data on 4,292 mammals, invertebrates, plants, fish, amphibians, and reptiles.
Fish species, including the thorny skate in the North Atlantic, have shown a trend toward smaller sizes, while smaller-bodied species like mackerel are increasing in abundance. The findings suggest a significant shift in the composition and functioning of ecosystems globally. Although fish exhibited the most noticeable size reduction, the phenomenon was also recorded in some plants and invertebrate species.
Researchers propose that global heating and overconsumption, characteristic features of the Anthropocene era, may be driving these changes. The study supports previous observations of shrinking fish sizes in the North Sea and smaller Pacific salmon in Alaska, potentially linked to the climate crisis.
Lead researcher Dr. Inês Martins from York University emphasized that the core finding indicates not just a predominant shrinking but a combination of species replacement and changes within species populations contributing to smaller organisms. The study revealed that within some species, individuals are progressively becoming smaller, and larger species are being replaced by smaller ones when they disappear.
The senior author of the paper, Prof Maria Dornelas of St Andrews University, highlighted the complexity of the observed changes, suggesting that when large organisms vanish, others attempt to fill their ecological niches and utilize the available resources. This phenomenon, known as species replacement, keeps the biomass constant, indicating that ecosystems are compensating for these alterations.
Dr. Franziska Schrodt from Nottingham University emphasized the need for more comprehensive data on various organisms beyond fish to draw clearer conclusions. The researchers stressed the importance of understanding the mechanisms involved in these changes, as shrinking body sizes can have significant consequences on how ecosystems function and how humans benefit from them. The study underscores the urgency for increased investment in research to explore food webs and other species interactions beyond fish.
