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Nature seems to favor the biggest and the smallest forms of life

New research from scientists at McGill University and the University of British Columbia have discovered that the majority of Earth’s biomass is concentrated in living organisms at either end of the size spectrum. 

The findings not only shed light on the fascinating range of life forms that exist on our planet, but also carry significant implications for understanding the impacts of climate change and human activity on global biomass.

Over the course of five years, the team of scientists meticulously compiled and analyzed data pertaining to the size and biomass of every type of living organism on Earth. Their subjects ranged from minuscule single-celled organisms, such as soil archaea and bacteria, to massive life forms like blue whales and sequoia trees.

What the researchers learned

The researchers observed that the pattern favoring large and small organisms was consistent across all species and more pronounced in land-based organisms as compared to those in marine environments. Intriguingly, they also found that maximum body size appeared to reach similar upper limits across various species and habitats (see image here).

“Trees, grasses, underground fungi, mangroves, corals, fish, and marine mammals all have similar maximum body sizes. This might suggest that there is a universal upper size limit due to ecological, evolutionary, or biophysical limitations,” explains lead author Eden Tekwa, a former postdoctoral fellow at the University of British Columbia who now works as a research associate with McGill University’s Department of Biology.

The study underscores the incredible diversity of life on our planet. Study co-author Malin Pinsky, an associate professor in the Department of Ecology, Evolution, and Natural Resources at Rutgers University, reflected on the astonishing range of sizes that living organisms can take. “If the tiniest microbe was the size of the period at the end of this sentence, the largest living organism, a sequoia tree, would be the size of the Panama Canal.”

Where humans fit on the spectrum

Humans, despite representing a relatively small biomass, belong to the size range that comprises the highest biomass, which is a relatively large body size. “Our size among all living things reveals our place in the global biome,” said Tekwa.

Understanding the distribution of body sizes among living organisms is crucial for gaining insights into the world around us, according to the researchers. 

Furthermore, these findings carry important implications for predicting how climate change and human activities may affect the planet’s biomass in the future.

“For example, fish biomass is probably half of what it was before humans arrived, but it gets harder and harder to infer those patterns as we go farther back in time,” explained Tekwa. “We need to think about how the distribution of body size biomass will change under environmental pressures.”

This comprehensive study not only offers a captivating glimpse into the vast range of living organisms on Earth, but also serves as a critical stepping stone towards understanding and mitigating the impacts of human activity and climate change on our planet’s delicate balance of life. The research is published in the journal PLOS One.

The impact of human activity on other Earth species

Human activity has had a profound impact on Earth’s millions of species, affecting their populations, habitats, and ecosystems. While some of these impacts are direct, others are indirect consequences of human actions. Here are some key ways human activity has influenced the planet’s biodiversity:

Habitat loss and fragmentation

The expansion of human populations and activities, such as agriculture, logging, mining, and urban development, has led to the destruction and fragmentation of natural habitats. This not only reduces the available space for all of Earth’s life forms, but also isolates populations, making it harder for them to maintain genetic diversity and adapt to changing environmental conditions.


Humans have been harvesting plants, animals, and other resources from nature for millennia. However, unsustainable practices, such as overfishing, deforestation, and poaching, have led to the depletion of many species’ populations, pushing some to the brink of extinction.


Industrial activities, agriculture, and waste disposal introduce harmful chemicals and substances into the environment. These pollutants contaminate air, water, and soil, affecting the health of various species and disrupting delicate ecosystems. For example, the widespread use of pesticides has caused declines in insect populations, which in turn impacts the food chain and disrupts ecosystems.

Climate change

Human activities, particularly the burning of fossil fuels, have led to a significant increase in greenhouse gas emissions. This has resulted in global warming and changes in weather patterns, which can lead to shifts in species’ ranges, altered migration patterns, and disrupted breeding cycles. Climate change can also exacerbate other threats, such as habitat loss and the spread of invasive species.

Introduction of invasive species

The movement of people and goods around the world has facilitated the spread of non-native species into new environments. These invasive species often outcompete native species for resources, disrupt ecosystems, and can even drive local species to extinction.

Disease transmission

Human activities can facilitate the spread of diseases among wildlife populations, either by increasing contact between species or by introducing pathogens into new areas. For example, deforestation and habitat fragmentation can force wildlife to live in closer proximity to humans and domestic animals, increasing the likelihood of disease transmission.

To mitigate the impact of human activity on Earth’s millions of other life forms, conservation efforts must be tailored to address these various threats. This includes habitat preservation and restoration, sustainable resource management, pollution control, climate change mitigation, and the control of invasive species. 

By working together, governments, businesses, and individuals can help protect the planet’s biodiversity and ensure the survival of countless species for generations to come.


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