Estimates

Before I start on the Defra reply, here is a short explanation which will help you see why what might seem to be a semantic quibble later on is actually crucial to knowing how much Lowland Meadow habitat exists.

When undertaking a field survey we have a set of categories that we can place plant communities into (the National Vegetation Classification (NVC)) and those plant communities may differ across a site depending on soil type, historic/current management, amount of water, etc.

Here is a straightforward example where the size of the national priority habitat Lowland Meadow (the greener bit with flowers in the photo and the green area on the map) is 0.22 ha and the size of the site is 1.3 ha. Please note that the size of the national priority habitat Lowland Meadow is not the same as the size of the site.

Exif_JPEG_PICTURE

Tot Fenny's Field cut

The Defra question arose out of my not understanding the published figures on how much Lowland Meadow habitat existed in England see https://theintermingledpot.wordpress.com/2018/01/07/documenting-ancient-grassland-loss-a-short-ish-review/  (at the end of the blog).

I thought for this blog I would just reproduce the questions and answers.

My question sent to Defra on 23 March 2018 was: –

“Has there been a change in the definition of Lowland Meadows in England as used by Defra in the figures published in 2017 https://www.gov.uk/government/statistical-data-sets/env09-england-biodiversity-indicators compared to the figures used from 2005 http://jncc.defra.gov.uk/page-5848  ?

I can see that for England in the 2016 statistics there is 36,129 ha of Lowland Meadows priority habitat and yet in 2005 there was 7282 ha.”

 

Their reply on 20 April 2018 was: –

“Thank you for your email of 23 March about the definition of Lowland Meadows in England.

There has been no definitional change. The Lowland Meadows Priority habitat covers the National Vegetation Communities MG4, MG5 and MG8.

Prior to explaining the apparent anomaly in the 2005 and 2016 figures, it is important to stress that since the late 1990s there have been various published estimates of the extent of different semi-natural grassland habitats in England and the UK based on different data sources and sometimes on differing definitions.

There are estimates that have been based on the partial data gleaned from Phase II (NVC -based) grassland surveys in England undertaken over the period 1980 – late 1990s. Thus, this is the source of the lower figure of 7, 282 ha which is cited in the UK BAP targets from 2006 archived on the JNCC website, and more recently in the semi-natural grasslands chapter of the National Ecosystem Assessment (2011). The English Nature Research Report 2000 ‘Monitoring the condition of lowland grassland SSSIs’ No. 315 gives a similar estimate of lowland meadows of 8,400 ha. The larger figure of around 36,000 ha is based on data from the SSSI site condition monitoring, England Priority Habitat inventories and agri-environment monitoring. This figure is much larger and this is largely due to the fact that polygons often do not strictly delimit the actual semi-natural grassland area and may include areas of semi-improved grassland or non-grassland habitats such as scrub. There may also be issues to do with definition such that some areas have been labelled as lowland meadows when in fact they are semi-improved or ‘undetermined’ grassland. Natural England, subject to resources, intends to continually refine the data on semi-natural grassland habitat definition, extent and condition.

However, for now, the smaller estimates of extent are likely to be a more accurate reflection of the extent of the lowland meadow Priority Habitat in England.”

 

And my reply on 26 April 2018 was: –

“Thank you for the very clear and thorough reply, which is much appreciated.

Whilst I genuinely appreciate the financial restraints that have been placed around accurately recording the extent and condition of the National Priority Habitat of Lowland Meadow, I will still point out the following error in the presentation of the current figures that Defra have decided, for whatever reason, to use.

If there has been no definitional change (as stated) then all the labelling in the tables after the measurement change should reflect the change that has occurred. i.e. the table records the (accurate) area of a site within which an (unspecified) amount of the target priority habitat occurs. For example, in ENV09 – England biodiversity indicators 2017 assessment, page 2a, the title states “Status of threatened habitats: Extent and condition of priority habitats” but the consequences of the reply are that the title should read “Status of threatened habitats: Extent of the site within which the [unspecified amount of] priority habitat is present and the condition of priority habitats within the site”. ‘Extent of priority habitat’ is not the same as ‘extent of the site in which priority habitat is present’. In the table, or as a footnote, I think Defra should also state what the estimate of the extent of each priority habitat type is and the date when that estimate was made and the data on which the estimate was based and make it clear that the priority habitat has not been adequately surveyed nationally to give an accurate figure of its extent and that the best information possible at the moment is an estimate based on old surveys. Or perhaps Defra could survey the priority habitats properly and publish that data.

There is obviously a similar issue with the presentation of the extent data regarding priority habitats within SSSIs.

Someone from Defra, in the interests of interdepartmental consistency within Government, might wish to discuss this issue with the Office for National Statistics to assist with this report  https://www.ons.gov.uk/economy/environmentalaccounts/methodologies/uknaturalcapitaldevelopingseminaturalgrasslandecosystemaccounts where Table 11 states clearly that there is 13,406 ha of Lowland Meadow within SSSIs in England “Source: Joint Nature Conservation Committee Protected Areas Designations Directory (2010)” and this is not the case; there is 13,406 ha of SSSI in which the priority habitat Lowland Meadow is present, but the extent of the priority habitat Lowland Meadow is not known. There seems also to be some confusion with the definition of semi-natural grassland (SNG) in Table 2 which apparently includes “…sown grassland strips alongside arable fields, long-term set-aside or fallow land…” enabling the comment that “SNG is a fluid habitat and can be readily converted to arable land and improved grassland through cultivation, re-sowing and fertiliser application. It can also be restored and recreated from arable or improved grassland precursors.” but later in part 11. Cultural Services states “Semi-natural grasslands (SNGs) are part of the cultural landscape of the UK. Most are remnants of traditional farming practices and are the product of thousands of years of human interaction with landscape and its wildlife.” Perhaps all the Government departments could use the same definition of Lowland Meadows.

The confusion apparent within the Office for National Statistics’ report neatly sums up the wide range of seemingly similar sets of data that are mislabelled, and the lack of accurate up-to-date knowledge on the extent and condition of the priority habitat Lowland Meadow.

Whilst I understand the (GIS mapping) reasons why they have arisen, I think that the present figures are not fit for the purpose of conservation of priority habitats, completely misleading in their presentation, and any policy based upon them will be flawed.

I will be blogging about the Defra answer and my above reply at https://theintermingledpot.wordpress.com/ as I mentioned in the original question on this topic sent to you on 19 January 2018 to which I didn’t receive a reply.“

 

If you have read this far and are wondering about how one of the wealthiest countries in the world has got to a point where the extent of one of its iconic ancient national priority habitats is not known, then let me remind you that how government money is allocated is a function of the politicians that we all elect; I can only assume that the politicians are not interested enough in our heritage to fund a survey to see what is actually there rather than use an estimate.

 

NOTES

Geographical Information Systems (GIS) is basically a big computerized map. All the habitat statistics now seem to report the size of the site (the ‘polygons’ mentioned in the reply), because that is known and easy to measure, rather than the size of the habitat within the site because that requires digitisation of a skilled site survey which would cost more.

The Excel table relating to ENV09 – England biodiversity indicators 2017 assessment can be downloaded from here https://www.gov.uk/government/statistical-data-sets/env09-england-biodiversity-indicators

The 2016 statistics showing 36,129 ha of Lowland Meadows priority habitat includes information from the Defra Higher Level Farm Scheme (HLS) – the agri-environment monitoring mentioned in the Defra reply. This scheme was appraised in the report that can be found here http://randd.defra.gov.uk/Default.aspx?Menu=Menu&Module=More&Location=None&ProjectID=19358&FromSearch=Y&Publisher=1&SearchText=grasslands&GridPage=3&SortString=ProjectCode&SortOrder=Asc&Paging=10#Description I haven’t read the whole report and I found the summary difficult to understand, but apparently not all the surveyed sample sites in HLS are national priority habitat, those that were non-priority habitat on entering HLS showed little progress (only 17% improved), HLS doesn’t make much positive difference in the majority of sites they surveyed. 16% of the 118 site sample “…were unsuitable for the establishment of species-rich grassland…”. Basically this is the bit where something in the figures is termed Lowland Meadow when it is not actually Lowland Meadow; obviously Lowland Meadow means Lowland Meadow except for those occasions when it doesn’t *sigh*. And also “50% of the HK6 sample were found to be correctly targeted (Group 3)…” which I took to mean the expertise at Defra was as good as tossing a coin, which must be wrong – so maybe lets just conclude that the advice to farmers from Defra is not perfect. Actually, what is really depressing is that there are some very skilled and knowledgeable people working within the Defra group and I wonder how much longer they will stay – we really do need them, because the situation would be abysmal (rather than just completely awful) if they weren’t there.

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6 Responses to Estimates

  1. Jon Mortin says:

    My limited experience of this issue may be relevant. Every year the LERC where I work would send an annual update of digitised Priority Habitats (including Lowland Meadow) to Natural England. Each year the data would have been updated based on recent survey data and sometimes re-assessed older survey data. Typically a digitised priority habitat would be one or more adjacent OS topo layer polygons and the assessment would generally be “polygon includes some of the priority habitat” ie also may include an area of other habitat. Trying to digitise the exact extent of Priority Habitat is often not practicable particularly if survey only done on one date (missing some key indicator species). Also if the area is less than 0.25ha it would not be deemed to meet the requirement for Priority Habitat Meadow. Since Natural England no longer fund LERCs they do not get these annual updates and so are not really in a position to monitor any subsequent changes. And although new survey data may have suggested an increase in total area of priority habitat, this would almost certainly not be a real increase because previously identified priority habitat would not have been re-assessed to see if it still met the definition.

    • Martin says:

      Thank you Jon – for reading, and for your comment which is very relevant. I had read about Natural England no longer funding Local Environmental Records Centres (LERCs) but had forgotten to include it in the blog and it will affect their future knowledge of Priority Habitats. As with anything, the digital data is only as useful as the habitat survey on the ground and the difference between a figure of around 8,000 ha actual (on the ground) Lowland Meadow and the current figure used (polygon includes some of the priority habitat) of 36,000 ha is so great as to make the 36,000 ha figure meaningless in terms of conservation as we will be unable to measure any change in amount of actual (on the ground) Lowland Meadow. I think we really do need a baseline (on the ground) national survey that can then be digitised.

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