Table 1.

Enumeration of biodiversity on Earth and in soil

Macrobes	Total species
	Lower	Central	Upper	Conf.
Mammalia	n/a	6.5 × 103 (16, 49)	4.5 × 104 (41)	H
Nematoda	5 × 105 (50, 51)	1 × 106 (33, 52)	1 × 108 (52)	L
Arthropoda	1.14 × 106 (53)	7 × 106 (32)	3 × 107 (54)b,?	M
Insecta	9.5 × 105 (53)	5-5.5 × 106 (32, 41)	1 × 108 (55)b,?	M
Arachnida	9 × 104 (53)	1.1 × 105 (41)	7.5 × 105 (50)	M
Collembola	6.5 × 103 (56)	8.7 × 103 (53)	5 × 104 (57)	M
Diplopoda	1.3 × 104 (53, 58)	1.5 × 104 (58)	7-8 × 104 (41, 59)	M
Isoptera	3 × 103 (53)	5.4 × 103 (60)	1 × 104 (7)	M
Formicidae	1 × 104 (53)	1.5 × 104 (61)	2.1 × 104 (62)	M
Oligochaeta	5 × 103 (63)	1 × 104 (64)	?	H
Enchytraeidae	7.1 × 102 (65)	7.8 × 102 (53)	1.2 × 103 (7)	H
Mollusca	8 × 104 (41)	1.2 × 105 (53)	2 × 105 (50)	H
Plantae	3.8 × 105 (53)	5.37 × 105 (64)	n/a	H
Microbesk	6.7 × 106,k	1.01 × 109,k	1 × 1012-14 (34, 66)?	L
Phage	1 × 108 (67)?	1 × 1011 (68)l,?	3.7 × 1011 (68)l,?	VL
Bacteria	4.3-4.5 × 106 (19, 39)	1 × 109 (17)	3.7 × 109 (43)n	L
Fungi	2.2 × 106 (35)	6.2 × 106 (69)	1.65 × 108 (42)p,?	M
Archaea	1.1 × 104 (70)	1.9 × 105 (19)r	3.8 × 105 (19)r	L
Protists	6 × 104 (55)	1-3 × 105 (12, 55, 71)	8.4-16.2 × 107 (42, 72)?	L
Total	1.1 × 108	1.01 × 1011	3.74 × 1011	L
Macrobes		Species in soil
Mammalia	75 (12)	250 (73)	?	H
Nematoda	2.15 × 105,a	4.65 × 105,a	5 × 107,a	L
Arthropoda	3.49 × 105 (12)	2.1 × 106,c	9.2 × 106,c	M
Insecta	2.88 × 105 (12)	1.67 × 106,c	3 × 106,c	M
Arachnida	4.32 × 104 (12)	5 × 104,d	3.5 × 105,c	M
Collembola	5.98 × 103 (74)e	8 × 103 (12)	8.18 × 103 (74)e	M
Diplopoda	1 × 104 (12)	1.15 × 104,c	6.15 × 104,c	M
Isoptera	2 × 103 (12)	4.9 × 103,f	9.5 × 103,f	M
Formicidae	5 × 103 (75)g	9 × 103 (12)	1.1 × 104 (75)g	M
Oligochaeta	3.3 × 103 (63)	6 × 103 (12)	?	H
Enchytraeidae	7 × 102,h	7.7 × 102 (12)	1.18 × 103,c	H
Mollusca	80 (12)	3.5 × 104 (76)i	6.4 × 104 (77)i	H
Plantae	3.2 × 105,j	4.66 × 105,j	n/a	H
Microbesk	6 × 106,k	4.4 × 108,k	?	L
Phage	5.6 × 106 (68)m,?	9.9 × 109 (78)m,?	1.59 × 1011,m,?	VL
Bacteria	9.5 × 105 (39)o	4.3 × 108,o	3.3 × 109,o	L
Fungi	2 × 106,q	5.6 × 106,q	n/aq	M
Archaea	1.1 × 103,s	3.6 × 104,s	1.9 × 105,s	L
Protists	2.4 × 104,t	8.3 × 104,t	n/at	L
Total	9.5 × 106	1.04 × 1010	1.62 × 1011	L

Species in soil include taxa that live in, on, or which complete part of their life cycle in soil. Values representing the most realistic predictions at the lower, central, and upper ranges are included based on literature review. For microbes, species concepts are based on direct counts or predictions of the most accepted molecular definitions of “species” (unless explicitly stated elsewise) represented as contigs, protein clusters, or viral OTUs for viruses, and 97% sequence similarity OTUs for protists, bacteria, archaea, and fungi. Note that each reference is shown in parentheses as a numeric value whereas methodological notes describing the estimations are shown outside of the parentheses using letters (SI Appendix, Table S10), where needed. Groups within a larger category are shown in italicized font. Question marks denote areas where we currently lack enough information to estimate. Not applicable (n/a) refers to lower and/or upper estimations that are obsolete or which do not make sense to estimate because there is no realistic lower or upper prediction due to a high confidence central prediction. In the absence of a value or where a value is highly speculative (e.g., upper fungal diversity), we used the central estimate to predict total species richness in soil. The confidence column (Conf.) reflects how well current data support predictions of species in soil within each group as very low (VL), low (L), mid (M), or high (H).