How Many Species Are on Earth? (Most Still Undiscovered)

Scientists estimate about 8.7 million eukaryotic species exist on Earth — and only ~1.9 million have been scientifically described. That means roughly 78% of life forms alive right now have no name, no paper, and no photograph. The gap is mostly insects, fungi, and deep-sea organisms.

Here's where that number comes from and why it's so shaky.

The 8.7 million estimate

This figure comes from a 2011 study by Mora et al., published in PLOS Biology. They extrapolated naming rates from taxonomic hierarchies — how many genera are in a family, how many species in a genus — and fit the curve backwards.

Confidence interval: between 7.4 and 10 million. Bacteria and archaea aren't counted (too different to describe with the same math).

What we've named so far

As of 2026:

• ~1.05 million animals (insects are 1 million of that)
• ~400,000 plants
• ~150,000 fungi
• ~300,000 microbes and protists

Species get named at about 18,000 per year. At that rate, reaching 8.7 million takes another 300+ years — if extinction doesn't win the race first.

Where the undiscovered species live

Three big pools:

Tropical insects

Rainforest canopy beetle surveys regularly find 40–60% of sampled species to be undescribed. Beetle estimates alone range from 1.5 to 2 million species.

Fungi

We've named 150,000 fungi. Actual estimate: 2–5 million. Most are microscopic, symbiotic with plants or insects, and impossible to identify without genetic sequencing.

Deep sea

95% of the ocean is unexplored. Every new trench dive finds new species — Challenger Deep expeditions in the 2020s described dozens of new amphipods and snailfish alone. See how deep is the ocean for depth scale.

Extinction is running ahead of discovery

The background extinction rate is 1–5 species per million per year. Current rate: 100–1,000x higher.

At current rates, up to 1 million species face extinction in the coming decades — many before they're named.

Why species counts matter

Diverse ecosystems are resilient ecosystems. A forest with 400 tree species handles a new fungal pathogen better than one with 4. Species redundancy = system stability.

Playable analog: try Ecosystem Builder and watch what happens when you yank a species out of a food web.

What counts as a species?

This is surprisingly unsettled. The classic definition (populations that interbreed and produce fertile offspring) breaks down for asexual species, ring species, and things that hybridize in the wild.

Taxonomists lose whole weeks arguing over this.

Why tracking new species is getting easier

Environmental DNA (eDNA) sampling lets researchers detect species from soil, water, or air samples without ever seeing the organism. 2026 studies catalog thousands of species per expedition — 10x the pre-2015 rate.

The backlog is still enormous. But the rate is accelerating.

For more biosphere context, see how does natural selection actually work. Or what if dinosaurs never went extinct.