[Syrphidae] IUCN Red list Hoverflies: calculation AOO

[Francis Gilbert]

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> 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
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