{"id":1984,"date":"2014-01-17T16:09:32","date_gmt":"2014-01-17T16:09:32","guid":{"rendered":"http:\/\/jeremyshiers.com\/blog\/?p=1984"},"modified":"2014-01-17T16:11:36","modified_gmt":"2014-01-17T16:11:36","slug":"where-early-saltmarsh-surveys-wrong-jan-2014","status":"publish","type":"post","link":"http:\/\/jeremyshiers.com\/blog\/where-early-saltmarsh-surveys-wrong-jan-2014\/","title":{"rendered":"Were Early Saltmarsh Surveys Wrong? – Jan 2014"},"content":{"rendered":"

DEFRA targetted EA with recreating 100 ha\/year saltmarsh by flooding farmland following saltmarsh surveys. Were surveys wrong?<\/p>\n

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Around 1973 there was a plan to build an airport on Maplin Sands off south Essex.\u00a0 The airport was never built but there was a lot of preparatory work, including aerial photographs of much of Essex coast and a report, the ecology of Maplin Sands<\/a>.<\/p>\n

In 1988 another aerial survey was conducted. Fiona Burd compared the 1973 and 1988 photographs and concluded saltmarsh there was 876.1ha in 1973 and 765.4ha in 1988 so saltmarsh was being lost at 7.4ha\/year.<\/p>\n

A further study was conducted by Nick Cooper in 1998 who found there was on 621.1 ha of saltmarsh so the rate of loss between 1988 and 1998 had doubled to 14.4ha\/year.<\/p>\n

Natural England conducted a saltmarsh survey<\/a>\u00a0\u00a0 in conjunction with University of Hull from 1997 to 2008.\u00a0EA also independently conducted a saltmarsh survey of UK<\/a> between 2006 and 2009.\u00a0 Both reports emerged in 2011.<\/p>\n

EA seems to be more than a little embarased that for the England and Wales as a whole their survey finds MORE<\/strong><\/span>\u00a0 saltmarsh than Fiona Burd did in 1988!\u00a0 Pretty embarassing for an organisation trying to justify their actions on the basis there is a national emergency<\/strong> over the rate saltmarsh is being eroded.<\/p>\n

Te he<\/p>\n

The following table sumarises the results of these surveys for Hamford Water.\u00a0 In this post I will concentrate on Hamford Water as it’s near where I live.<\/p>\n<\/div>\n\n\n\n\n\n\n\n\n\n
survey<\/th>\ndate<\/th>\nha saltmarsh<\/th>\n<\/tr>\n
maplin sands<\/td>\n1973<\/td>\n876.10<\/td>\n<\/tr>\n
burd<\/td>\n1988<\/td>\n765.40<\/td>\n<\/tr>\n
iecs start<\/td>\n1997<\/td>\n694.82<\/td>\n<\/tr>\n
cooper<\/td>\n1998<\/td>\n621.10<\/td>\n<\/tr>\n
iecs end<\/td>\n2008<\/td>\n698.13<\/td>\n<\/tr>\n
ea<\/td>\n2006-2009<\/td>\n674.81<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The next table sumarises rates of saltmarsh loss between different surveys ASSUMING saltmarsh was lost at a constant rate.<\/p>\n\n\n\n\n\n\n
period<\/th>\nstart ha<\/th>\nend ha<\/th>\ngain\/loss ha<\/th>\nrate gain\/loss ha\/year<\/th>\n<\/tr>\n
1973-1988<\/td>\n876.10<\/td>\n765.40<\/td>\n-110.70<\/td>\n-7.38<\/td>\n<\/tr>\n
1988-1998<\/td>\n765.40<\/td>\n621.10<\/td>\n-255.00<\/td>\n-14.43<\/td>\n<\/tr>\n
1997-2008<\/td>\n694.82<\/td>\n698.13<\/td>\n+3.31<\/td>\n+0.03<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

I have chosen these three sets of start and end dates as<\/p>\n

    \n
  1. The first row caused everyone to panic and to start flooding farmland in an attempt to recreate saltmarsh.\u00a0 DEFRA targetted EA with creating 100ha\/year in UK,
    \n40 ha\/year in East Anglia.<\/li>\n
  2. The second row caused them to panic even more especial as by now UK had signed EU Habitats Directive which apparently meant we had to recreate saltmarsh by “EU Law”<\/li>\n
  3. The final row made them realise there was no reason to panic but\u00a0 DEFRA doesn’t seem to have gotten around to telling EA to stop flooding farmland yet.<\/li>\n<\/ol>\n

    Are The Numbers Right<\/h2>\n

    There is a clear difference between the rates of loss\/gain found by the different surveys.<\/p>\n

    This may be due to uncertainty in measurement.\u00a0 No measurement is ever completely accurate and it is standard practice to quote a measurement along with and indication of uncertainty (commonly called error – though error in this context does not mean mistake).<\/p>\n

    For example\u00a0 876 \u00b1 20 ha.\u00a0 Rather than just 876.01.<\/p>\n

    Another issue all undergraduate scientists are warned about is not to confuse accuracy with precision.\u00a0 In other words if you can only measure to within \u00b120ha, which means your result may be anywhere within a 40ha range, there is no point in quoting your result to 1 decimal place, not least because it makes you look silly.<\/p>\n

    The assumption saltmarsh (which consists of plants) dies of at a constant\u00a0 rate is almost certainly wrong.\u00a0 Just about every gardener will be familiar with plants coming and going.\u00a0 In particular plant growth is dependent on weather and seasons.<\/p>\n

    There is no indication of what time of year the saltmarsh surveys were conducted or even if they were conducted at the same time of year.<\/p>\n

    Apart from this I have a huge problem with the 255ha loss claimed by Cooper between 1973 and 1998.\u00a0 It’s just to big.<\/p>\n

    Now lets go back to basics what\u2019s a ha (hectare)?\u00a0 It\u2019s a square 100 metres by 100 metres.<\/p>\n

    Here I have superimposed a grid where the light black squares\u00a0 are approximately 100 x 100 metre.\u00a0 The larger dark black squares are\u00a0 1 km x 1km.<\/p>\n

    \"gridMap\"<\/a><\/p>\n

    Now can you pencil in 255 little squares to indicate which might have had saltmarsh eroded?<\/p>\n

    The squares have to be in places which are covered by the sea at high tide, well at least spring high tides.<\/p>\n

    I think the figure quoted is probably as much as 100 times to large.\u00a0 Perhaps they counted in a few fields by mistake.<\/p>\n

    The snappily titled EnglishNature Report710<\/a> discusses some of the shortcomings in the earlier reports.<\/p>\n

    Natural England Survey<\/h2>\n

    The report of Natural England survey included maps of different regions where<\/p>\n