Concerning an upcoming blog post with a slightly related subject, I would like to add the corresponding Biogeographic realms to all natural and mixed WHS. I hope there's some knowledgeable (amateur) biologist out here who can help me with the following questions:

1. Is it still the 'best' choice to use Udvardy's division of biogeographic realms?

2. While visiting Iriomote Island WHS last week, I was intrigued to find out that it is part of the Indomalayan realm and the other islands of that serial WHS are part of the Palearctic realm. I have been looking for other WHS spread across multiple realms to create a new connection. So far I found Socotra, but do you know of a third?

Gulf of California:

Upper Gulf of California - Colorado River Delta (marine portion): Nearctic realm
Islas Marietas: Neotropical realm

"This cluster of islands is situated in a transitional zone between the Nearctic and Neotropical biogeographic regions"
https://lacgeo.com/islas-marietas-national-park-reserve

Almost any of the lists of "biogeographic realms" seems to have problems - New Zealand gets moved around from Australasian to Antarctica in Udvardy lists I have been searching (originally the latter). And it also has a separate (?) "Biome" list of 14 divisons. (Do we do both? But need to keep separate if so). There is also a "subset" of Udvardy below the orignal 8 ("The Udvardy system further subdivides the eight Biogeographic Realms into 193 Biogeographical Provinces") . Then there are the "The IUCN/SSC Global Habitat Analysis" and "WWF Global 200 Ecoregion" lists. We would really need to agree a list to use for the exercise. If we start using a "mix" we will get very muddled! The bigger the list we choose to assign the harder the job......? The Udvardy 8 seems a good place to start? Also - you suggest doing it for all Natural and Mixed sites - but is it relevant for purely fossil or geological sites?. They don't really possess a contemporary or relevant "BIO"geographical aspect. To do so would be a bit like assigning Cathedrals to the Biogeographic region in which they are situated?!!

The 2004 Report "Future priorities for a credible and complete list of natural and mixed sites" identifies a range of approaches/lists - I noticed also this comment within it "3 WH sites (Air Ténéré, Everglades and Manas) overlap two realms so the total number of sites is inflated from 172 to 175.". Unfortunately the report doesn't contain a full list of how IUCN allocated its Udvardy realms as of c2004 which would have been a great help. But surely there must be a list somewhere on the Web??

Ah! - Found this - with a map assigning WHS up to 2002 to Udvardy realms. It isn't very readable unfortunately (there may still be better somewhere?) - but its colours also help with identifiying WHS sitting at the junctions of Udavardy realms - e.g Gulf of California and Socotra (which is 3 way I think?). It also confirms Manas, Everglades and Air/Tenere as "junction sites".

This is true of course, but still it is often used that way to geographically categorize natural places. And there would hardly be natural WHS without any reference to biodiversity.

But is that "Biodiversity" relevant to the current Realm - e.g Messel Pit?

Hi Els, I thought of contributing to your first question: Is it still the 'best' choice to use Udvardy's division of biogeographic realms?

I wouldn't say it is the 'best' choice, but you can certainly use it because of its utility and convenience. The fact that some current biology and biogeography textbooks refer to, use, and discuss Udvardy's biogeographic realms suggests that it is still relevant and usable to understand biogeography and ecosystems. It's not merely framed as a "historical" system/framework/classification. Note that there are other biogeographical systems/frameworks/classifications, such as Pielou (1979). I don't think there could ever be a 'best' system or framework for biogeographic regions, because biogeographic realms do not have defined edges/boundaries. I have to remind myself of the journal article I was reading years ago that kinda mentioned this. I'll have a look, or probably call my professor in biogeography.

Note that Udvardy's biogeographic realms are terrestrial, but we gotta recognise that there are marine and freshwater biogeographic realms as well. To add more fun, there are also phytogeographic realms (aka floristic kingdoms) and zoogeographic regions too. :)

Also, a realisation: "biogeographic realms" and "habitats" seemingly being used interchangeably often confuse me. My mind often differentiates the two, where biogeographic realms take into account the historical distribution and evolutionary history of organisms, while habitats merely pertain to places/regions that have similar biological and physical geographical features (e.g., contemporary distribution of animals/plants, substrate type, moisture, climate).

Anyway, since Solivagant mentioned the IUCN Global Habitat Analysis, I thought of sharing IUCN Ecosystem Typologies. This is a super cool reference to the different terrestrial and marine ecoregions/habitats across the globe. I know governments use this as a reference for conservation and environmental management stuff. I'd do too.

Thanks for your reply, carlosarion. The IUCN Ecosystem Typologies look cool indeed, I wonder whether IUCN already did a mapping of the WHS?

Due to the criticisms brought forward by Solivagant and you, I will not introduce one of the more classical biogeographical realms like Udvardy's. Still, I wonder why it is still used that often. It seems just a nerdy way of dividing the world into continents. Mammalwatching.com was using it until 2022 (they've since gone to countries as their main categories), although there clearly are marine mammals too...

Further to this and its relationship to WHS, this article might be of interest "A systematic approach for defining thematic groups of World Heritage properties to support the strategic management of threats".

The authors took the 44 Natural WHS in Africa as a case study for developing an approach and tried to identify natural thematic groups appropriate for their purpose and then allocated these to the WHS. They faced the sorts of problems stated above by carlosarion regarding the variety of types of "realm" which need to be covered (or at least "considered") - as in this quote "Development of the final list of thematic groups also considered biome typologies from the IUCN Global Ecosystem Typology report..... customised to the UNESCO Africa Region and its specific natural features. Whilst our analysis was predominated by habitat-related thematic groups, non-habitat themes were also incorporated"

The net result is that most Natural WHS (in Africa at least!) cover a surprisingly wide range of of "themes" .... rather I suppose like cities cover a wide range of historical periods and architectural features. Whilst some WHS are inscribed for 1 very "simple" reason, most exhibit a complex variety of natural/cultural aspects, all of which, it could be argued. are required to maintain the entire site with its "as inscribed" OUV - even if the headline "OUV" only highlights something smaller. The more one tries to "simplify" a site by adopting a shortlist of types for defining its "essence" the more one deviates from the complex reality! We of course have already faced this "problem" with our simplified "Categories" for WHS.
Here is a grid of the 44 African WHS allocated to Natural themes
And here the full report

IMO, the report doesn't provide encouragement for us to get further involved in trying to allocate Natural WHS to "groupings". Let's just stick with Udvardy and our current categories (perhaps with some slight adjustments?) and keep an eye on what others, more knowledgeable than most of us, do!

PS During my searches for the above I came across this rather nice IUCN map of Natural/Mixed WHS propertires highlighting their "Conservation Status" but also providing quick links to IUCN data about each - the drill downs include very detailed maps of separate locations within each WHS e.g this example taken at random (scroll down) for the Cape Floral WHS. Unfortunately not all WHS are documented (as yet?) to that level of detail - so it can't be used to identifiy the boundaries of e.g the Hyrcanian Forests - so it is back to the Nomination files for such as them!