The question of how many plant species exist worldwide is complex, reflecting both the limits of human exploration and the constant re-evaluation of scientific data. Providing a single, fixed number is impossible, as the count represents a dynamic estimate. The total number of plant species is a constantly moving target, fluctuating based on new discoveries, advances in technology, and ongoing taxonomic debates. Understanding this complex picture requires defining what constitutes a plant, where these species are concentrated, and why the number changes so frequently.
The Current Global Estimate
The most widely accepted figures focus specifically on vascular plants, which include all plants with specialized tissues for transporting water and nutrients. Scientists estimate that there are currently between 350,000 and 450,000 species of vascular plants on the planet. Databases contributing to the World Flora Online project indicate that approximately 376,000 species have been formally discovered and validly described.
This total is comprised of major groups, with flowering plants, or angiosperms, accounting for the vast majority at over 350,000 species. Ferns and lycophytes contribute roughly 14,000 species, while conifers and other gymnosperms add over 1,000 species. The difference between the described species and the higher estimates represents the fraction of plant life scientists predict still awaits discovery, primarily in under-explored regions.
Defining the Plant Kingdom
The specific species count depends heavily on the scientific definition used, which is often narrower than the common understanding of “plant.” The Kingdom Plantae, or Viridiplantae (green plants), generally refers to land plants and the green algae from which they evolved. Global species counts primarily focus on Embryophytes, or land plants, and most often, the vascular plants within that group.
Groups sometimes confused with plants are typically excluded from these biodiversity totals. For instance, fungi now belong to their own distinct kingdom, as do various groups of algae, which lack the complex tissues of land plants. Focusing the count on vascular plants allows researchers to deal with a more manageable and taxonomically cohesive group for global inventory efforts.
Why the Count Remains Fluid
The total number of plant species is constantly being revised for multiple interconnected reasons. A primary factor is the steady discovery of new life, as remote or under-explored areas, particularly in the tropics, continue to yield previously unknown species. Botanists estimate that up to 20% of all vascular plant species may still be undescribed, with new species being formally published at a rate of around 3,000 per year.
Beyond new discoveries, the count changes because of taxonomic revisions, a process described using the terms “lumping” and “splitting.” Splitters divide one broadly defined species into two or more distinct species, while lumpers consolidate separate species into a single, broader group. New tools, such as DNA barcoding, amplify this effect by revealing previously unrecognized genetic differences, often leading to the splitting of species that look identical.
Finally, the loss of species due to extinction is another factor, though the rate of discovery often outweighs the number of confirmed losses. Plant extinction rates are estimated to be far above the historical background rate. Recent extinctions are concentrated in small, isolated populations on islands or in areas of extreme habitat loss. This makes the number of known species a balance between the addition of newly described plants and the subtraction of those lost forever.
Geographical Distribution of Diversity
The world’s plant species are not evenly distributed; they are heavily concentrated in specific areas known as biodiversity hotspots. These regions have exceptionally high levels of species richness and endemism, meaning a large number of species are found nowhere else on Earth. To qualify as a hotspot, a region must harbor at least 1,500 endemic vascular plant species and have lost a significant portion of its original habitat.
Examples include tropical rainforests, such as the Amazon and Congo basins, and regions with Mediterranean climates, like the Cape Floristic Region in South Africa. The Cape Floristic Region is globally recognized for its immense plant diversity and high rates of endemism, despite its relatively small size. These hotspots collectively cover only a small percentage of the Earth’s land surface but contain a disproportionate majority of all plant life.
In contrast, regions like polar areas and large deserts exhibit much lower species diversity due to extreme environmental conditions. This uneven distribution means that efforts to catalog the world’s remaining undescribed species focus on these threatened, hyper-diverse tropical and subtropical zones.