Life exists in a multitude of different shapes and sizes, but new research just published in ‘PLOS ONE’ has just revealed that some sizes are more ‘popular’ than others. Or, put more properly, our planet’s biomass (the material that makes up all living organisms) tends to be concentrated at the two ends of the size spectrum, that is, in the largest and smallest organisms. Something that is valid for all species.
This is the first scientific work of its kind, and has been carried out by experts from the Universities of British Columbia and McGill, in Canada, and Rutgers, in the United States. During the study, the research team examined the body sizes of all living organisms on Earth and discovered the unexpected pattern.
“The fact that life on Earth comes predominantly packaged in two sizes is an astonishing discovery,” he explains. Malin Pinsky, co-author of the study. Sometimes it seems like mosquitoes, flies or ants rule the world, and yet when we did the numbers, we found that our planet is dominated by microbes and trees. Those are the silent partners that recycle nutrients and replenish the air around us.”
“The smallest and largest organisms significantly outperform all others,” says Eden for her part. Tekwa, lead author of the research. This is a new and emerging pattern that needs to be explained, and we have no theories on how to do it at this time. Current theories predict that biomass is evenly distributed over all possible body sizes.”
five years of work
To get their results, the researchers spent five years collecting and analyzing data on the size and biomass of every type of living thing on the planet, from the smallest single-celled organisms, such as soil archaea and bacteria, to the largest organisms. big, like blue whales and redwoods. In this way, they found that the pattern that favors larger and smaller organisms holds across all types of species, and is more pronounced in terrestrial organisms than in marine ones.
“The largest body sizes,” Tekwa continues, “occur in multiple groups of species, and their maximum body sizes are all within a relatively narrow range. Trees, grasses, subterranean fungi, mangroves, corals, fish, and marine mammals have similar maximum body sizes, which could suggest a universal upper size limit exists due to ecological, evolutionary, or biophysical constraints.”
In addition to challenging our understanding of how life is distributed on Earth, these results have important implications for predicting, among others, the effects and impacts of climate change. “Body size – says Tekwa – governs many global and local processes, including the rate at which carbon is sequestered and how the function and stability of ecosystems can be affected by the composition of living things.”
The study also yields some intriguing details about how life is distributed in various types of ecosystems. For example, in coral reefs. “Although corals are found in only a small fraction of the ocean,” Tekwa explains, “it turns out that they have about the same biomass as all the fish in the world. Which illustrates how important the balance of ocean biomass is. Corals support a huge diversity of fish, so it’s really interesting that those two organisms have almost the same biomass.”
And what about humans? We have known for a long time that, although we dominate the planet, our biomass is relatively small. But our size in relation to that of all living things has also revealed our position in the global biome. In Tekwa’s words, “we belong to the size range that comprises the highest biomass, which is a relatively large body size.”