[Syrphidae] IUCN Red list Hoverflies: calculation AOO

[w.v.steenis at casema.nl]

Hi Wout,

 

The IUCN red list frame work consists of many papers and guidelines. 

In the attached mapping standards 1.16 (2018) the IUCN explicitly states in 7.2 (pages 21 and 22) that you should use 2x2 km squares for the AOO.

Also in the 2024 IUCN Red List Guidelines this is stated in 4.10 (page 54). 

 

Cheers,

 

Wouter

 

Van: Syrphidae <syrphidae-bounces at lists.nottingham.ac.uk> Namens Francis Gilbert
Verzonden: vrijdag 6 november 2026 12:54
Aan: wout.opdekamp at gmail.com; Syrphidae at lists.nottingham.ac.uk
Onderwerp: Re: [Syrphidae] IUCN Red list Hoverflies: calculation AOO

 

I have ver 12 (2016) of the guidelines, where it says “in many cases a grid size of 2 km (cell area 4 km²) is an appropriate scale. ... For most cases we recommend a scale of 4-km² cells as the reference scale” (p.47)

 

This is what I have used as a standard for assessing the Egyptian fauna.

 

Francis

 

 

Dr Francis Gilbert

Emeritus Professor, School of Life Sciences, University of Nottingham, Nottingham NG72RD, UK

website: https://www-web.nottingham.ac.uk/~plzfg/

 

From: Syrphidae <syrphidae-bounces at lists.nottingham.ac.uk <mailto:syrphidae-bounces at lists.nottingham.ac.uk> > On Behalf Of wout.opdekamp at gmail.com <mailto:wout.opdekamp at gmail.com> 
Sent: 06 November 2026 10:59
To: Syrphidae at lists.nottingham.ac.uk <mailto:Syrphidae at lists.nottingham.ac.uk> 
Subject: [Syrphidae] IUCN Red list Hoverflies: calculation AOO

 

Hi,

 

I'm trying to find more detailed information on how the Area of Occupancy has been assessed in the IUCN Red List. Unless I misread this information is lacking. In Version 3.1 of the  IUCN RED LIST CATEGORIES AND CRITERIA attention is drawn to the fact that assesment scale impacts the outcome but without giving general guidelines.

 

More specifically I would like to know which AOO would be attributed to a species known from for instance 10 fragmented (>5km distance between patches) patches of suitable habitat. Let's say individual patch vary in size but never exceed 5ha.

 

Could anyone clarify this?

 

 

Regards,

 

Wout

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