How Many Different Species Of Animals Are On Earth
Humans make upwards just 0.01% of Earth's life – what'south the rest?
Our planet is home to an incredible diversity of organisms. What does Earth's biodiversity look similar in the big flick?
In this post I provide an overview – with summary graphic – of Earth's biomass, how it is distributed between taxa (the taxonomic group of organisms), and the environments within which they live. This summary is based on the findings of research by Bar-On, Phillips & Milo published in theProceedings of the National University of Sciences (PNAS).1
Humans account for just 0.01% of biomass
There are several ways we can answer the question of how much life is on Globe. We could, for example, count the number of species, population sizes or the number of individual organisms. Just these metrics tin can make information technology hard to compare between taxa: small organisms may accept a large population but nevertheless account for a very minor percentage of Globe'south organic thing.
For a meaningful comparison, Bar-On et al. (2018) quantified life using the metric of biomass. Biomass is measured here in tonnes of carbon every bit it is a primal edifice-block of life.2
In the graphic beneath I summarize the distribution of global biomass by taxonomic kingdom (on the left), with a magnified snapshot of the animate being kingdom (on the right).
What are the stand-out points?
- plants – mainly trees – boss life on Globe: they business relationship for more than 82% of biomass;
- surprisingly in second place is the life we cannot see: tiny bacteria sum up to 13%;
- whilst our perceptions are ofttimes focused on the brute kingdom, it accounts for just 0.4%;
- humans account for but 0.01% of biomass, then we'd need about 70 trillion of usa to match Earth's collective biomass.three
Livestock outweighs wild mammals and birds ten-fold
Humans incorporate a very modest share of life on Globe — 0.01% of the total, and 2.5% of animal biomass [animal biomass is shown in the right-hand box on the visualization higher up].
But we are likewise responsible for the animals we raise. Humans lone may seem insignificant, simply our hunger for raising livestock means we accept played a major role in shifting the balance of brute life: livestock account for 4% of animal biomass.iv
Livestock accounts for more biomass than all humans on Earth; more than l% greater than humans.
And livestock accounts for much more than all wildlife: Wild mammals and birds collectively account for only 0.38% — livestock therefore outweighs wild mammals and birds by a factor of x.5
Oceans, land and deep subsurface: how is life distributed across environments?
The visualization here provides a snapshot of how life spans beyond the planet's environments. This summary is based on the findings of research by Bar-On, Phillips & Milo published in theProceedings of the National Academy of Sciences (PNAS).6
There are three loftier-level habitat environments: land, marine, and deep subsurface environments. Deep subsurface environments tin be terrestrial or beneath the ocean floor, just represent habitats deep below the surface – extending from around 50 metres to thousands of metres below the surface.7
Almost of life exists on land — 86% of biomass. This is because almost all constitute life – generally trees – is terrestrial. The authors guess that marine plants, for example seaweed, make upward less than 1 billion tonnes of carbon. This is less than 0.2% of total plant biomass.8 Almost bacteria and archaea exists in the deep subsurface, meaning 13 percentage of global biomass thrives in this environment.
Despite dominating our planet in terms of surface area and book – taking up more than 70% of global surface area – the oceans are home to just 1% of biomass. Only they exercise boss the beast kingdom: 78% of animate being biomass lives in the marine environs.
With lifeforms ranging in size from the microscopic cellular level to large lifeforms that span tens of hectares,ix it is impossible to contextualize life on Earth through experience or intuition alone.
But look at the viruses that live in the ocean: while each one of them is tiny, if we placed all the viruses finish-to-terminate they would stretch for 10 one thousand thousand light years. That is around 100 times the distance across our ain milky way.10 On land the scale is just as mindblowing: at that place are more than 1016 prokaryotes in a ton of Earth's soil – orders of magnitude more than the 'mere' 10eleven stars in our galaxy.11
Looking at the big numbers allows us to sympathise our planet and our identify in it.
How many species are in that location?
How many species have we described?
Before nosotros look at estimates of how many species in that location are in full, we should also enquire the question of how many species we know that nosotros know. Species that we take identified and named. This is only a fraction of the actual number of species on Earth because there are so many that we haven't yet found or studied.
The IUCN Red List tracks the number of described species and updates this figure annually based on the latest work of taxonomists. In 2020 it listed 2.12 million species on the planet. In the chart we run across the breakdown beyond a range of taxonomic groups – 1.05 meg insects; over 11,000 birds; over 11,000 reptiles; and over 6,000 mammals.
These figures – particularly for lesser-known groups such every bit plants or fungi – might be a bit as well high. This is because some described species finish up existence synonyms – the description of already-known species, simply given a separate name.12 There is a continual evaluation procedure to remove synonyms (and most are removed eventually), but oft species are added at a faster charge per unit than synonyms can be plant and removed.thirteen To give a sense of how large this effect might be, in a study published in Science, Costello et al. (2013) estimated that around xx% of the described species were undiscovered synonyms (in other words, duplicates).14 They estimated that the 1.nine million described species at the time was actually closer to one.v 1000000 unique species.
If we were to assume this "20% synonym" figure held true, our 2.12 million described species might actually be closer to ane.seven meg.
Regardless, nosotros know that any of these figures are an underestimate of the actual number of species. The fact that there are then many species that nosotros've yet to discover has real consequences for our ability to empathise changes in global biodiversity and the rate of species extinctions. If we don't know that certain species exist, nosotros also don't know that they might have, or will presently, go extinct. Some species will inevitably go extinct before we realise that they existed.
How many species are there really?
How many species do nosotros share our planet with? It's such a bones and fundamental question to understanding the world around us. It's most unthinkable that we would not know, or at least have a expert gauge, what this number is. But the truth is that it's a question that continues to escape the world's taxonomists.
As Robert May summarised in a newspaper published in Science fifteen:
If some alien version of the Starship Enterprise visited Earth, what might exist the visitors' first question? I think it would be: "How many distinct life forms—species—does your planet have?" Embarrassingly, our best-gauge answer would be in the range of v to x 1000000 eukaryotes (never mind the viruses and bacteria), but we could defend numbers exceeding 100 million, or every bit low as 3 meg.
Over decades, researchers take fabricated a number of broad-ranging estimates. As May points out, this ranges anywhere from 3 to 100 meg – two orders of magnitude of difference. Most modernistic estimates autumn within a tighter range.
I of the nigh widely-cited figures comes from Camila Mora and colleagues; they estimated that in that location were around eight.vii million species on Earth today. 16 Mora et al. put an dubiousness of 1.3 million species effectually this figure. The breakdown of how many of these species are animals; fungi; plants; and other groups is shown in the table. This too shows the split between marine and terrestrial environments. It's estimated that 2.2 million of these species lived in the ocean.
At that place are also a range of other estimates: Costello et al. (2013) approximate v ± 3 million species; Chapman (2009) estimates 11 million; and subsequently reviewing the range in the literature, Scheffers et al. (2012) choose non to requite a concrete figure at all.17 There is typically strong agreement on the almost well-studied taxonomic groups such as mammals, birds, and reptiles. Where virtually of the disagreement lies is in insects, fungi, and other smaller microbial species. Reaching consensus on such pocket-size and inaccessible lifeforms is undoubtedly hard.
How can we even brainstorm to brand these estimates? There are several approaches that researchers take.
Mora et al. (2011) – whose estimates are shown in the tabular array – used the fact that in that location are anticipated relationships in higher taxonomic classifications of life, that could exist extrapolated to the species level. Life can exist classified at multiple levels: each belongs to a kingdom (e.g. the "Animalia" kingdom – this sorts life into animals, plants, fungi etc.); then a phyla (e.g. "Mollusca" or "Arthropoda" in the animal kingdom); then grade; order; family; genus; and finally the species level. We know much more than about the college taxonomic classifications (kingdoms, phylum; classes) than we do about the specific species-level breakdowns. But, nosotros find that for groups of species that have been well-studied, we find predictable patterns between the higher taxonomic classifications, and estimates at the species-level. Researchers can employ these predictable patterns for well-known species and apply them to lesser-known groups.
The honest answer to the question, "how many species are there?" is that we don't really know. Some estimates bridge several orders of magnitude, from a few to 100 million. But near contempo estimates lie somewhere in the range of around 5 to ten million.
| Kingdom | Number of species (Ocean) | Number of species (Terrestrial) | Number of species (Full) |
| Animals | 2,150,000 | 5,620,000 | 7,770,000 |
| Chromists | 7400 | twenty,100 | 27,500 |
| Fungi | 5320 | 605,680 | 611,000 |
| Plants | 16,600 | 281,400 | 298,000 |
| Protozoa | 36,400 | 0 | 36,400 |
| Archaea | 1 | 454 | 455 |
| Bacteria | 1320 | 8360 | 9680 |
| Total species | 2,210,000 | vi,540,000 | 8,750,000 |
Biodiversity across the world
The globe is abode to millions of species, each adjusted to different environments: tropical, temperate, polar; terrestrial; freshwater or marine; high or low altitude; dry; wet or a mixture of both. Most places on Earth are home to at least some unique species, but the density of biodiversity varies a lot across the world's continents.
The following maps show the density of endemic species by country across a range of taxonomic groups. Owned species are those that naturally occur in just one geographical locations. In other words, they are unique to that place.
What we run across is that the tropics is incredibly dense in unique wildlife. In almost every map nosotros meet a bright belt along the equator – this is truthful of mammals, birds, coral reefs, amphibians and a range of fish species. It's estimated that tropical forests alone are habitation to more than half of the planet'southward species.19 This is of import because, unfortunately, this likewise where the greatest threats to wildlife exist today. It'southward where 95% of deforestation occurs, and where the most mammals, birds, amphibians and reptiles are hunted and poached. If we want to protect these species nosotros need to first understand where they alive; what the pressures are; and what we tin can do about it.
Explore more of our work on Biodiversity
Source: https://ourworldindata.org/biodiversity-and-wildlife
Posted by: rossarman1993.blogspot.com
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