In a sweeping global analysis encompassing thousands of animal and plant species, a concerning trend has emerged: species across the board are shrinking in size. Researchers have pinpointed this phenomenon most prominently in fish, which are undergoing significant reductions in size.
The study reveals striking changes in various species. For instance, the thorny skate, a North Atlantic fish known to grow up to a meter in length, has seen a reduction in size. Conversely, smaller-bodied species like mackerel are experiencing a surge in numbers, altering the composition and dynamics of ecosystems.
Although the phenomenon of shrinking is primarily observed in fish, it has also been documented in some plant and invertebrate species. On the flip side, certain species, like Arctic plants, are increasing in size.
GLOBAL HEATING AND CONSUMPTION
While the exact causes of these size changes, some of which exceed 10%, are still under investigation, researchers propose that global heating and overconsumption, hallmarks of the Anthropocene, our current geological epoch shaped by human impact on Earth, may be contributing factors.
This study aligns with previous findings of diminishing fish sizes in the North Sea and smaller Pacific salmon in Alaska, believed by some to be linked to the climate crisis. The comprehensive research, published in the journal Science, was conducted by an international team of scientists representing 17 universities, drawing data from 4,292 species, including mammals, invertebrates, plants, fish, amphibians, and reptiles, encompassing a wide range of seabed species.
Dr. Inês Martins from York University, the lead researcher, noted, “The core finding is that body size is not only predominantly shrinking, but organisms are becoming smaller due to a combination of species replacement and changes within species populations.” She emphasized the most pronounced trends in fish, where shrinking body size is evident. While data for other organisms is more limited, there are unmistakable changes in biodiversity and its patterns.
The study suggests that small numbers of large organisms are being replaced by many smaller ones, maintaining biomass levels, underscoring the idea that ecosystems adapt to these changes.
Prof. Maria Dornelas of St. Andrews University, a senior author of the paper, emphasized the complexity of these shifts, stating, “Recognizing and exploring this complexity is imperative if we want to understand the mechanisms involved in how body size is changing through time.”
The consequences of organisms becoming smaller are profound, as the size of animals plays a pivotal role in how ecosystems function and how they benefit humans. Larger fish, for example, have the potential to feed more people than smaller ones.
Dr. Franziska Schrodt from Nottingham University, another co-author, emphasized the need for more comprehensive data, especially for organisms beyond fish, to draw clearer conclusions. Future research, particularly in the context of food webs and species interactions, will benefit from expanding these measurements.