Unlike census takers, scientists don’t have to go door-to-door to calculate the number of living species on the planet. For the first time they are using new “technological advances in genetic analysis” to obtain a more accurate estimate and have included microorganisms into the count.
Older estimates were based on efforts that dramatically under-sampled the diversity of microorganisms. Until recently, we’ve lacked the tools to truly estimate the number of microbial species in the natural environment. The advent of new technology provides an unprecedentedly large pool of new information. Before high-throughout sequencing (rapid sequencing of whole genomes), scientists would characterize diversity based on 100 individuals, when we know that a gram of soil contains up to a billion organisms, and the total number on Earth is over 20 orders of magnitude greater.
Over 5.6 million species were sampled from the world’s landmasses and oceans, excluding Antarctica. Biologists from the United States compiled over 35,000 separate analyses of microscopic (including single cell bacteria and archnaea) and non-microscopic species. Yet, only 1-percent of all species have been identified.
Estimating the number of species on Earth is among the great challenges in biology. Our study combines the largest available datasets with ecological models and new ecological rules for how biodiversity relates to abundance. This gave us a new and rigorous estimate for the number of microbial species on earth.
Studies were conducted in conjunction with the United States National Institutes of Health’s Human Microbiome Project, Tara Oceans Expedition and the Earth Microbiome Project. This led to researchers developing a new scaling estimate to forecast the number of undiscovered life forms that exist in similar environments.
The study states.
Ecological scaling laws are intensively studied for their predictive power and universal nature but often fail to unify biodiversity across domains of life. Using global-scale compilation of microbial and microbial data, we uncover relationships of commonness and rarity that scale with abundance at similar rates for microorganisms and microscopic plants and animals. We then show a unified scaling law that predicts he abundance of dominant species across 30 orders of magnitude to scale of all microorganisms on earth. Using this scaling law combined with the lognormal model of biodiversity, we predict that Earth is home to as many as 1 trillion microbial species.
That leaves 99.999% of all species yet to be discovered.
Lennon sums up,
Our analysis suggests there are more microbial species on Earth than there are stars in the galaxy.