An adult I'iwi in Hawaii

Endemic and Native Species in Hawaii

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Hawaiian endemic species are species that only exist in Hawaii and in the surrounding waters. You will not be able to see these species in the wild in any other place of the world, except perhaps in a zoo.

One of the often quoted facts about Hawaii is that over 90% of its native species are endemic. That sounds good, right? But what does it mean? And is it even true?

To answer this we first need to talk about what we mean with ‘endemic’ and ‘native’. Afterward, we dive into the scientific literature to check the facts on Hawaiian species and conclude with an evolutionary comparison between Hawaii and the famous Galapagos islands:

The quick answer is that the claim is partially true. About 90% or all native species that live on land in Hawaii are indeed endemic. However, when talking about all species on Hawaii, this number drops to a still very respectable 40%.

90% of all Native Species on Hawaiian soil are Endemic. We check the Facts! #earthporntwitter shareclick to tweet

Native (endemic and non-endemic) and alien species

When talking about the incredibly diverse nature in Hawaii it is good to know the difference between native (endemic and non-endemic) and non-native (alien) species.

Native” means that a species occurs naturally within a region. Either because they evolved there or because they arrived without human assistance. For example, the I’iwi bird shown below is native (and endemic!) to the Hawaiian islands.

An adult I'iwi in Hawaii
The I’iwi bird is endemic to Hawaii. Source: I’iwi|Pu’u o’o Trail | 2013-12-17at12-43-209 by HarmonyonPlanetEarth, licensed under CC BY 2.0

Native species can be split into endemic and non-endemic species. Endemic in biology means that a species is unique to a defined geographical location. Practically this means that a non-endemic native Hawaiian species have been found in ecosystems outside of Hawaii. Endemic species only can be found in Hawaii.

Alien species finally are introduced from outside ecosystems and can be harmful to local species because they compete for the same resources. Alien species are also called non-native or invasive species. In Hawaii, there are about 5000 non-native species (source).
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How many species are there in Hawaii?

The Bishop museum has been surveying the biodiversity in Hawaii since 1992 through the good work of the Hawaii Biological Survey.

Following their latest survey in 2014 (source), there is a total of 26608 species in the state of Hawaii! Between 10000 and 10500 of those species are endemic. There are also ~5000 non-native species, which leaves a grand total of ~11000 native species that are not endemic.

If you do the math on the number above, you will see that between 37 and 40% of all species on Hawaii are endemic, and ~50% of all native species are endemic. Why is this different from the 90% mentioned above?

Well, as always, the devil is in the details, and those details seem to have been lost along the way. Species are often split into different groups based on taxonomy or living habitat. If you look only at the native species living on land (terrestrial species), you will recover the 90% number.  Marine species spread more easily (living on an island doesn’t stop them!), which lowers the number of endemic species.

You can see a breakdown of all the species that make up the Hawaiian biodiversity below. Note the few % difference between the totals shown in the last row with the more recent 2014 results that we mentioned earlier.

Totals Endemic Alien Species at risk Extinct
Algae + other protists 2013 82 18 0 0
Fungi and lichens 2088 240 ? 0 0
Flowering plants 2264 918 1101 654 97
Other plants 766 241 47 0 0
Molluscs 1339 962 96 127 500
Insects 8427 5462 2609 289 74
Other arthropods 1191 366 735 4 0
Other invertebrates 4003 822 253 7 0
Fish 1216 149 73 1 0
Amphibians 8 0 8 0 0
Reptiles 27 0 23 0 0
Birds 294 63 53 36 88
Mammals 44 2 19 2 2
Totals 23680 9307 5035 1120 761
Hawaiian species numbers by taxonomic group and conservation state. (2003, Table 1. Reproduced from source)

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Hawaii vs the Galapagos islands: who wins the game of evolution?

Whether the number of endemic species is 40%, 50% or 90% doesn’t matter that much. Hawaii still is a champion if it comes to the number of endemic species!

Take for example the Galapagos islands. These South American islands have been made famous by Darwin as a showcase of evolution, and rightfully so. However, when compare the Galapagos with Hawaii it becomes clear that there are far more endemic species on Hawaii:

Comparison of the endemic diversity of the Galapagos islands (left) with Hawaii (right). Adapted from Table 2 in Allen Allison 2003, Org. Divers. Evol. 3, 103–110 (2003), doi:10.1078/1439-6092-00065
Comparison of the endemic diversity of the Galapagos islands (left) with Hawaii (right). Adapted from Table 2 in Allen Allison 2003, Org. Divers. Evol. 3, 103–110 (2003), doi:10.1078/1439-6092-00065

Of course, this makes sense when you consider that [a] the Hawaiian islands have more different climate zones (8/13, see our article on Big Island climate zones), and [b] that the Galapagos are less isolated than Hawaii.  Hawaii is located 2390 miles from the nearest continent, and the Galapagos islands “only” 600 miles.

Another fun takeaway from the figure is the incredible amount of endemic land snails (99.5%), beetles (99.4%), grasshoppers, and crickets (98.2%) on Hawaii!

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Resources used in this article

The writing of this article would not have been possible without the following resources: