More Trees Than Stars: Earth's Forests Are Larger Than the Milky Way

How We Counted the Trees

For most of human history, a precise count of Earth's trees was impossible and probably seemed unnecessary. The 2015 Nature study that produced the 3 trillion figure changed that. Led by Thomas Crowther at Yale University, the research combined satellite imagery, ground-based forest surveys from 50 countries, and computational modeling to produce the most complete tree census ever attempted.

The number was shocking. Previous estimates had placed the global tree count at around 400 billion — still impressive, but only about the same as the star count in the Milky Way. The new methodology, which accounted for forest density data across different biomes rather than simply extrapolating from total forested area, produced a figure roughly seven to eight times larger. Boreal forests in Russia and Canada, tropical forests in South America and central Africa, and the often-overlooked trees of dry savannas and woodlands all contributed to the dramatically higher total.

The Milky Way's Stars: A Number With Enormous Error Bars

Counting stars in the Milky Way is, paradoxically, harder than counting Earth's trees. We live inside the galaxy, which means we can only see a fraction of it directly — the rest is obscured by dust clouds and the galaxy's own disk. Astronomers estimate the Milky Way's star count primarily by measuring the galaxy's total mass, estimating what fraction of that mass is in stars, and then applying an average stellar mass to produce a population figure.

Current estimates range from about 100 billion to 400 billion stars, with many astronomers settling on approximately 200 to 300 billion as the most defensible middle range. The enormous spread reflects genuine uncertainty rather than imprecision in the measurement tools. Different assumptions about the population of dim, low-mass red dwarf stars — which may be far more numerous than previously thought — can shift the estimate dramatically. At 3 trillion versus approximately 300 billion, Earth's trees outnumber Milky Way stars by a factor of around 10.

Why Trees Are So Numerous

The diversity and resilience of tree-producing ecosystems across Earth's surface explains the vast number. Tropical rainforests — particularly in the Amazon basin, the Congo, and Southeast Asia — contain extraordinarily dense tree populations, sometimes 400 or more trees per hectare in mature forest. Boreal forests in the subarctic regions of Russia, Canada, and Scandinavia cover some of the largest continuous landmasses on the planet. Even ecosystems not conventionally thought of as forests — African savannas, Mediterranean woodlands, riparian zones along rivers — contribute billions of trees to the global count.

Trees are also ancient survivors. The evolutionary lineage of tree-form plants extends back roughly 350 million years, and modern trees are the product of continuous adaptation to enormously varied environments. Certain individual trees are thousands of years old. The Pando aspen grove in Utah, while technically a single clonal organism connected by a shared root system, contains about 47,000 individual stems and has been growing for an estimated 80,000 years.

The Shadow Behind the Statistic

The Crowther study's 2015 findings included a deeply sobering secondary result. The researchers estimated that the pre-agricultural Earth — before humans began large-scale land clearing — contained approximately 5.6 trillion trees. The current 3 trillion figure represents a reduction of nearly 46 percent over the approximately 12,000 years since farming began to transform landscapes. Humanity is currently removing approximately 15 billion trees per year through deforestation, agricultural clearing, and urban development, while planting roughly 5 billion, for a net loss of 10 billion trees annually.

The comparison between trees and stars remains genuinely impressive. But the more important number embedded in the same research is the scale of what has already been lost — and how quickly the gap between 3 trillion and whatever comes next continues to grow.