How Many Species of Plants Are in the Amazon Rainforest?

The most rigorous verified count puts the number of seed plant species in lowland Amazon rainforests at roughly 14,000, with close to 7,000 of those being trees. But that figure almost certainly underestimates the real total. Large swaths of the basin have barely been surveyed by botanists, species discovery curves show no sign of leveling off, and molecular tools keep revealing species that look identical to the naked eye but are genetically distinct. A reasonable working estimate for all plant species, including herbs, shrubs, epiphytes, and lianas alongside trees, likely runs well above 20,000 and possibly much higher.

What the Verified Checklists Show

The clearest single number comes from a taxonomically verified species list published in 2017. Researchers collated checklists from across lowland Amazonia and confirmed 14,003 seed plant species, of which 6,727 were trees.¹ That tree count lined up reasonably well with independent estimates. An earlier study focusing on the Brazilian Amazon alone estimated about 11,210 tree species with trunk diameters above 10 centimeters.² A separate checklist that tracked every known Amazonian tree taxon from herbarium records spanning three centuries arrived at 11,676 valid species names drawn from over 530,000 unique collections made between 1707 and 2015.³

These figures broadly agree: somewhere around 11,000 to 14,000 tree species, and a larger number when you fold in non-tree seed plants. The spread between estimates mostly comes down to how broadly “Amazonia” is defined geographically, whether the study restricted itself to lowland rainforest or included transitional zones, and how aggressively the researchers pruned duplicates and errors from their lists.

Why the True Number Is Almost Certainly Higher

Every one of those checklists acknowledges it is incomplete. The Amazon basin is enormous, roughly the size of the contiguous United States, and botanical collection effort has been wildly uneven. An analysis of collecting patterns found that 43% of Amazonia’s total area remains effectively uncollected, meaning no botanist has ever gathered specimens there. Another 28% is poorly collected, and only about 2% qualifies as relatively well sampled.⁴ That leaves an extraordinary amount of forest where new species could be waiting.

The rate at which new species are being described reinforces the point. A study of species discovery curves in Amazonia found that they do not fit the kind of flattening-out pattern you would expect if scientists were approaching the finish line. Instead, the curves remain steep, heavily influenced by individual taxonomic revisions that describe many species at once based on recently gathered material.⁵ In practical terms, every major field campaign in an under-sampled region still turns up species that are new to science.

Zooming out to all Brazilian flowering plants, not just the Amazon, researchers estimated the national catalog is 19 to 23% incomplete, with roughly 7,000 to 9,600 species still awaiting formal description.⁶ The Amazon’s share of those undiscovered species is likely substantial, since the basin accounts for a disproportionate fraction of Brazil’s remaining unexplored territory.

The Problem of Counting What You Cannot Identify

Even when botanists physically collect a specimen, identifying it to the species level can be surprisingly difficult. Many tropical trees can only be reliably identified when they are flowering or fruiting, yet the vast majority of specimens gathered during ecological surveys are sterile, meaning they lack those diagnostic features. A review of tropical South American plant data found that more than half of all known species are represented by fewer than ten herbarium records, and roughly one in five species is known from just a single specimen.⁷ With sample sizes that thin, many species are essentially invisible to ecological modeling and conservation planning.

Taxonomy itself introduces uncertainty in both directions. Historically, botanists sometimes described the same species more than once under different names because they were working from limited material in different regions. Conversely, what appears to be one widespread species sometimes turns out to be several distinct ones once someone examines it closely. A striking example involves Amazonian palms. Researchers tracking every species description and subsequent revision found that roughly 800 heterotypic synonyms, meaning names that turned out to refer to species already described, have been collapsed into just 175 currently recognized Amazonian palm species. Most of those corrections happened after the mid-1990s, causing an 80% drop in palm species counts within three decades.⁸

A similar cleanup of the broader Amazonian tree checklist removed about 23% of previously listed names, which turned out to be synonyms, misspellings, non-Amazonian species, or non-trees that had been incorrectly included.³ So the count is not simply rising over time. It is being refined, sometimes sharply downward for individual groups, even as genuinely new species continue to be added.

A Forest Dominated by a Handful of Species

One of the most surprising findings about Amazonian plant diversity is how unevenly individuals are distributed among species. A landmark study based on more than 1,100 forest plots scattered across the basin found that just 227 tree species, about 1.4% of the total, are so common that together they account for half of all individual trees in Amazonia. At the other extreme, the rarest 11,000 or so species collectively make up just 0.12% of trees.⁹

This “hyperdominance” pattern means that if you walk through the forest and identify every tree you pass, you will encounter the same common species again and again while the rare ones are maddeningly elusive. Many of those rare species have tiny populations, narrow ranges, or both, making them difficult to study and vulnerable to local extinction. The pattern also helps explain why the total species count is so hard to pin down: the species that are hardest to find are precisely the ones most likely to be missing from checklists.

Different Forests, Different Floras

The Amazon is not a single uniform canopy. It is a patchwork of forest types shaped by hydrology, soil chemistry, and elevation. Terra firme forests, which sit on well-drained upland soils and are never seasonally flooded, are consistently the most species-rich. Várzea forests, flooded seasonally by sediment-rich white-water rivers, support an intermediate level of diversity. Igapó forests, flooded by nutrient-poor black-water rivers, are the least species-rich of the three major lowland types.¹⁰

Soil chemistry is a powerful driver of which species grow where. Research across 19 forests in the western Amazon showed that canopy chemistry, the mix of defensive compounds, structural molecules, and rock-derived nutrients in leaves, shifts systematically along gradients of elevation and soil fertility. Communities on different soils evolve distinct chemical “signatures,” and those differences trace back along evolutionary lineages, suggesting that soil adaptation has been shaping the flora for millions of years.¹¹ A related study found that co-occurring tree species in an Amazonian forest plot tend to differ from each other in key functional traits more than you would expect by chance, pointing to niche-based processes that actively maintain diversity by allowing ecologically distinct species to coexist.¹²

Soil also matters for predicting how species will respond to climate change. Models that include detailed soil data predict Amazonian species ranges far more accurately than models using climate variables alone. The tight link between certain species and specific soil types could make it harder for plants to migrate in response to shifting rainfall patterns, because suitable soils may not exist in the direction they need to move.¹³

How the Amazon Became So Diverse

The Amazon’s plant richness did not appear overnight. Its deep roots stretch back tens of millions of years, and the rise of the Andes Mountains was a pivotal driver. As the Andes rose along Amazonia’s western edge, the uplift reshaped drainage systems, created enormous wetland barriers that isolated populations for millions of years, and eventually opened corridors that allowed northern plant lineages to disperse southward.¹⁴ The vast influx of Andean sediment into the basin created a patchwork of soil types, and on that diverse geological substrate, a spectacular array of plant communities took hold, particularly in western Amazonia, which remains the most species-rich part of the basin today.¹⁵

The fossil record from the Neogene period suggests that plant composition in Amazonia has shifted substantially over time, with an overall decline in diversity during cooler, drier phases. Molecular studies of Amazonian plant lineages paint a mixed picture: some groups show steady speciation rates over time, while others experienced bursts or slowdowns linked to climate cooling or rising Andean elevation.¹⁶ The Amazon’s current diversity is not a steady-state equilibrium. It is the product of a long, dynamic history of creation and loss, shaped by geological upheaval and climate swings stretching back well before the ice ages.

DNA Barcoding and the Hunt for Cryptic Species

Traditional taxonomy relies on visible features like leaf shape, flower structure, and bark texture. But in a forest where unrelated species can look remarkably similar and closely related species can look quite different, visual identification has limits. DNA barcoding, the practice of using short standardized gene regions to identify species, is increasingly used to fill in the gaps.

A barcoding project in the Serra dos Carajás region of the eastern Amazon generated DNA sequences for 1,130 specimens covering 538 species across 115 plant families, with 344 of those species being barcoded for the first time.¹⁷ Another study focused on two species of the genus Carapa, a commercially valuable timber tree, and found that trees identified as two morphologically distinct species showed strong genetic divergence, confirming that what field botanists had suspected based on appearance held up at the molecular level.¹⁸

An earlier effort to barcode Amazonian trees tested whether DNA sequences could reliably identify saplings, which are especially difficult to identify by eye because their leaves often look nothing like the adult form. The researchers were able to assign about 46% of juvenile trees to a known species using DNA alone, and combining molecular and visual data raised the identification rate to 59%.¹⁹ That still leaves a large fraction unidentifiable, partly because reference libraries are so incomplete. The unmatched saplings could include species not yet barcoded or, in some cases, species not yet described. As reference databases grow, barcoding will likely reveal additional cryptic diversity hiding in plain sight.

Why the Amazon Outpaces Other Tropical Forests

Tropical rainforests are the most species-rich terrestrial ecosystems on Earth, but the three great rainforest regions are not equally diverse. The Neotropics, with the Amazon as their centerpiece, hold more plant species than the tropical forests of Southeast Asia, which in turn outpace those of continental Africa.²⁰ Africa’s relative species poverty has puzzled biologists for decades. Multiple explanations have been proposed, including Africa’s drier and more variable climate during glacial periods, smaller remaining forest area, and differences in geological history and soil fertility. The Amazon likely benefits from its massive continuous area, its complex soil mosaic created by Andean sediment, and a long, relatively stable period of warm, wet conditions that allowed speciation to outpace extinction over millions of years.

Threats to the Flora

Deforestation and land-use change are the most immediate dangers. Predictions vary widely depending on the model and deforestation scenario used. One study estimated that by 2050, habitat loss would reduce the range available to Amazonian plant species by roughly 12 to 24%, committing 5 to 9% of species to eventual extinction.²¹ A more recent and sobering analysis, which overlaid species distribution models with both historical and projected deforestation, concluded that 36 to 57% of all Amazonian tree species likely qualify as globally threatened under international conservation criteria. If confirmed, that finding alone would increase the number of threatened plant species worldwide by about 22%.²²

The gap between 5% and 57% is not just a modeling disagreement. It reflects fundamentally different assumptions about how much deforestation will occur, how species are distributed across the landscape, and what “committed to extinction” means on the timescales being considered. What both studies agree on is that the rare species concentrated in heavily deforested areas face the greatest risk, and the hyperdominance pattern described earlier means a large share of Amazonian diversity lives in small, vulnerable populations.

Indigenous Lands as Repositories of Undiscovered Diversity

A striking finding from recent research is that indigenous territories may harbor much of the Amazon’s undiscovered flora. The study estimating that Brazil’s flowering plant catalog is 19 to 23% incomplete also found that indigenous lands safeguard about half of the areas with the highest potential for new species discoveries.⁶ This is partly because indigenous territories tend to be located in the remote, under-collected parts of the basin, but also because indigenous communities have maintained forest cover far more effectively than surrounding areas.

Indigenous peoples have also been documenting plant diversity in their own way for millennia. An ethnobotanical study of food plants used by the Huni Kuĩ people in the western Brazilian Amazon cataloged 89 species, and about 30% of the species that could be cross-checked against the scientific literature had never before been documented as food plants in any published study.²³ Traditional knowledge systems like these represent a parallel record of plant diversity and utility that formal science has only begun to tap, and they underscore that the question of “how many species” is intertwined with the question of who is doing the looking and what they consider worth noticing.