13.1.1. How Many Species are there on Earth and How Many in India?

Since there are published records of all the species discovered and named, we know how many species in all have been recorded so far, but it is not easy to answer the question of how many species there are on earth. According to the International Union for Conservation of Nature and Natural Resources (IUCN) (2004), the total number of plant and animal species described so far is slightly more than 1.5 million, but we have no clear idea of how many species are yet to be discovered and described.

Scientists have recorded over 1.5 million plant and animal species that have been identified and described. However, the total number of species on Earth is uncertain because many species are still undiscovered. The difficulty arises from the vast biodiversity present, especially in tropical regions, where many species have not yet been studied and categorized.

Imagine exploring a massive library but only having cataloged a small fraction of the books. While some books (species) are easily found and described, many others remain hidden in the stacks, waiting for someone to discover and document them.

Estimates vary widely and many of them are only educated guesses. For many taxonomic groups, species inventories are more complete in temperate than in tropical countries. Considering that an overwhelmingly large proportion of the species waiting to be discovered are in the tropics, biologists make a statistical comparison of the temperate-tropical species richness of an exhaustively studied group of insects and extrapolate this ratio to other groups of animals and plants to come up with a gross estimate of the total number of species on earth.

Estimates of undiscovered species can vary significantly, often depending on where scientists focus their studies. In temperate regions, many species have been documented, while the tropics, which are often far richer in biodiversity, remain less explored. Biologists use known data from well-studied species, especially insects, to infer the potential number of species in less studied groups, providing educated estimates on the total species count.

Think of it like attempting to calculate how many different types of fruit exist in a large orchard. If you only assess one section thoroughly (temperate areas) while ignoring others (tropical areas), your total count will be limited and likely underestimate the true diversity.

Some extreme estimates range from 20 to 50 million, but a more conservative and scientifically sound estimate made by Robert May places the global species diversity at about 7 million. Let us look at some interesting aspects about earth’s biodiversity based on the currently available species inventories. More than 70 per cent of all the species recorded are animals, while plants (including algae, fungi, bryophytes, gymnosperms, and angiosperms) comprise no more than 22 per cent of the total.

While the estimates of global species diversity vary greatly—from 20 million to possibly as high as 50 million—scientist Robert May suggests that there might be around 7 million species in total. Of these, a majority (over 70%) are animals, with plants making up a smaller fraction (22%). This shows that animals, particularly insects, are far more diverse than plant species.

Consider a huge party where most of the attendees are wearing unique costumes (animals), while only a handful are dressed in formal wear (plants). The party is vibrant and festive, but the vast majority of unique presentations come from those in costumes, symbolizing the rich diversity of animal species compared to plants.

It should be noted that these estimates do not give any figures for prokaryotes. Biologists are not sure about how many prokaryotic species there might be. The problem is that conventional taxonomic methods are not suitable for identifying microbial species and many species are simply not culturable under laboratory conditions.

When considering biodiversity estimates, prokaryotic life forms (like bacteria) are often excluded because scientists find it challenging to count them accurately. Traditional methods used to classify species are ineffective for microbes, and many cannot be cultured outside their natural environments, making it difficult to determine how many exist.

Think of it like figuring out how many different types of music exist in a vast collection. If many artists (bacteria) refuse to perform live or cannot be recorded (cultured), it becomes challenging to assess how many unique sounds (species) are present in the overall collection.

Although India has only 2.4 per cent of the world’s land area, its share of the global species diversity is an impressive 8.1 per cent. That is what makes our country one of the 12 mega diversity countries of the world. Nearly 45,000 species of plants and twice as many of animals have been recorded from India.

Despite comprising only a small portion of the Earth’s land area, India boasts a remarkable 8.1% of the world's total species diversity. This makes India one of the 12 recognized megadiversity countries, with approximately 45,000 recorded plant species and even more animal species, underlining the richness of its ecosystems.

Imagine a small garden that contains a surprising variety of flowers and plants compared to the vast park nearby. While the park may cover more land, the garden's compact area showcases an incredible concentration of unique species, just like India's rich and diverse natural heritage.

How many living species are actually there waiting to be discovered and named? If we accept May’s global estimates, only 22 per cent of the total species have been recorded so far. Applying this proportion to India’s diversity figures, we estimate that there are probably more than 1,00,000 plant species and more than 3,00,000 animal species yet to be discovered and described.

Utilizing Robert May's estimate that only 22% of all species have been documented, researchers speculate that India may have over 100,000 undiscovered plant species and around 300,000 undiscovered animal species. This highlights the extent of biodiversity that remains uncharted, emphasizing the need for continued exploration and conservation.

Consider a hidden treasure chest filled with countless gems (species) waiting to be found. Just because many have yet to be discovered doesn’t mean they don’t exist; ongoing exploration is essential to uncover the riches hidden beneath the surface.

Would we ever be able to complete the inventory of the biological wealth of our country? Consider the immense trained manpower (taxonomists) and the time required to complete the job. The situation appears more hopeless when we realize that a large fraction of these species faces the threat of becoming extinct even before we discover them.

Completing a comprehensive inventory of India's biodiversity is daunting due to the shortage of taxonomists—scientists trained to classify species—and the extensive time needed for thorough study. Compounding this issue is the alarming rate of species extinction, meaning many organisms may vanish before they are ever identified.

Imagine trying to catalog every book in a vast library, but each day, more books are being permanently removed from the shelves. This urgency heightens the pressure to document what we can before it's too late, illustrating the race against time in biodiversity conservation.

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