How Many Species on Earth?

Scientists estimate there are about 8.7 million eukaryotic species on Earth (animals, plants, fungi, and protists), plus potentially millions more bacteria and archaea. Of those 8.7 million, only about 1.5 million have been formally described and named. That means roughly 86% of land species and 91% of ocean species have not been discovered yet. We know more about the surface of Mars than we know about the life in our own oceans.

New species are described at a rate of about 15,000-18,000 per year, which sounds impressive until you do the math: at that pace it would take over 400 years to catalog everything. Meanwhile, species are going extinct at 100-1,000 times the natural background rate. We are losing species faster than we can find them. A significant number will vanish before science ever knows they existed.

The most species-rich group by far is insects. There are roughly 5.5 million insect species (estimated), of which about 1 million have been described. Beetles alone may have 400,000 species, prompting the biologist J.B.S. Haldane to reportedly quip that God has "an inordinate fondness for beetles." Plants have about 400,000 known species. Mammals, by comparison, have only about 6,500, and we discover only a handful of new ones each year.

🌿 Species by Group

🔬 How Many Species Have We Actually Discovered?

Scientists have formally described about 2.1 million species, but the estimated total is 8.7 million (plus or minus 1.3 million). That means roughly 75% of all species on Earth havent been discovered yet. The biggest gaps are in insects, fungi and deep-sea organisms. About 18,000 new species are described every year, but at that rate it would take centuries to catalog everything.

🦕 How Many Species Have Gone Extinct?

Over 99% of all species that have ever lived on Earth are now extinct. Scientists estimate that roughly 5 billion species have existed over Earths 4.5-billion-year history. The current extinction rate is estimated to be 100 to 1,000 times higher than the natural background rate, leading many biologists to call this period the sixth mass extinction.

🌍 Where Do Most Species Live?

🌴 Why Do Tropical Forests Have the Most Species?

Tropical forests cover only about 7% of Earths land surface but contain roughly half of all known species. The combination of year-round warmth, abundant rainfall and millions of years of stable climate has allowed evolution to produce extraordinary diversity. The Amazon rainforest alone contains about 10% of all species on Earth, including 40,000 plant species, 1,300 bird species and 3,000 types of fish.

🐠 How Many Species Are in the Ocean?

An estimated 2.2 million species live in the ocean, but only about 240,000 have been formally described. The deep ocean below 200 meters is the least explored habitat on Earth. Every deep-sea expedition discovers new species, sometimes dozens in a single dive. The ocean covers 71% of the planet but remains more mysterious than the surface of Mars in many ways.

🔬 Scientists Discover About 18,000 New Species Every Year

Despite centuries of exploration, we are far from done cataloging life on Earth. In 2023 alone, scientists described roughly 18,000 new species, including 126 new fish species, 68 new amphibians, and thousands of insects. Many new species are found not in remote jungles but in museum collections, where specimens collected decades ago are re-examined with modern DNA analysis and found to be distinct species that were previously lumped together.