From wout.opdekamp at gmail.com Fri Nov 6 10:58:46 2026 From: wout.opdekamp at gmail.com (wout.opdekamp at gmail.com) Date: Fri, 6 Nov 2026 11:58:46 +0100 Subject: [Syrphidae] IUCN Red list Hoverflies: calculation AOO Message-ID: 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: From marija.milicic at dbe.uns.ac.rs Fri Nov 6 11:42:22 2026 From: marija.milicic at dbe.uns.ac.rs (=?UTF-8?Q?Marija_Mili=C4=8Di=C4=87?=) Date: Fri, 6 Nov 2026 12:42:22 +0100 Subject: [Syrphidae] IUCN Red list Hoverflies: calculation AOO In-Reply-To: References: Message-ID: <7f4a36d2-fccd-40e5-b65f-6993d968dc53@dbe.uns.ac.rs> Hi Wout, AOO is calculated using a standard 2 ? 2 km grid overlaid on the species' distribution points. In some cases, a different grid cell size may be more appropriate depending on the biology and ecology of the species or taxonomic group, but 2 ? 2 km is the standard recommended by IUCN, and the one used in IUCN Red List of hoverflies. Each grid cell in which the species is present counts as 4 km?, regardless of the number of records within it or the actual size of the occupied habitat. So, in your example, if the 10 habitat patches fall within 10 different grid cells, the AOO would be 40 km?, even if each patch is smaller than 5 ha. There are also online tools available for calculating AOO, such as this one: https://geocat.iucnredlist.org/editor. You can simply upload your species occurrence records as a CSV file with coordinates, and the tool will calculate the AOO automatically. Hope this is helpful. Best, Marija On 11/6/2026 11:58 AM, wout.opdekamp at gmail.com wrote: > 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 > > _______________________________________________ > Syrphidae mailing list > Syrphidae at lists.nottingham.ac.uk > https://lists.nottingham.ac.uk/mailman/listinfo/syrphidae -- dr Marija Mili?i? Senior Research Associate University of Novi Sad BioSense Institute dr Zorana ?in?i?a 1 21000 Novi Sad, Serbia e-mail:?marija.milicic at biosense.rs marija.milicic at dbe.uns.ac.rs mmmarija88 at gmail.com tel: +381 (0)64 48 49 132 From Francis.Gilbert at nottingham.ac.uk Fri Nov 6 11:54:25 2026 From: Francis.Gilbert at nottingham.ac.uk (Francis Gilbert) Date: Fri, 6 Nov 2026 11:54:25 +0000 Subject: [Syrphidae] IUCN Red list Hoverflies: calculation AOO In-Reply-To: References: Message-ID: I have ver 12 (2016) of the guidelines, where it says ?in many cases a grid size of 2 km (cell area 4 km?) is an appropriate scale. ... For most cases we recommend a scale of 4-km? 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 On Behalf Of wout.opdekamp at gmail.com Sent: 06 November 2026 10:59 To: 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: From w.v.steenis at casema.nl Fri Nov 6 14:39:26 2026 From: w.v.steenis at casema.nl (w.v.steenis at casema.nl) Date: Fri, 6 Nov 2026 15:39:26 +0100 Subject: [Syrphidae] IUCN Red list Hoverflies: calculation AOO In-Reply-To: References: Message-ID: <022701dd6dfc$9f695710$de3c0530$@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 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 km?) is an appropriate scale. ... For most cases we recommend a scale of 4-km? 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 > On Behalf Of wout.opdekamp at gmail.com Sent: 06 November 2026 10:59 To: 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: IUCN Red List Mapping_Standards_Version_1.16_2018.pdf Type: application/pdf Size: 626608 bytes Desc: not available URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: IUCN RedListGuidelines 2024 version 16.pdf Type: application/pdf Size: 1716070 bytes Desc: not available URL: