Offsetting Ancient Woodland

Looking at the pronouncements on possible ratios of replacement trees to original trees, I wonder if the Government has seriously considered the areas of land required to offset loss of ancient woodland? Using some basic calculations, it seems to me that they are going to have to require some major areas of the countryside to be allocated to tree planting if they are serious about a 100:1 replacement ratio.

I have just done some 'back of a fag packet calculations (thankfully I gave up 10 years ago, so I have to use scrap paper but I doubt that makes much difference to the science!) and the following figures come up:

1. In traditional coppice with standards, tree density is likely to be anywhere between 30 and 100 crowns per hectare. That, I suspect refers solely to the 'standards' and thus the question must be whether additional provision needs to be made for the coppice stools?

2. Working on a density of 65 crowns per hectare as a median, that suggests that the Government is proposing a compensation ratio of 6.5 ha for every 1 lost to development. This is a ratio that far exceeds any so far for displacing migratory waterfowl.

3. If the pastiche is to replicate ancient woodland, then there also needs to be management to create the mix of coppice stools and standards. What needs to be borne in mind from an ecological perspective is that the coppice stools form a substantial part of the ecological value. This is largely underground and comprises the decaying timber that supports many fungi and the animals whose larvae feed on the fungi and bacterial soup that results.

4. It follows that the offset will require intensive management, unless of course we are simply looking at replacing an ancient woodland with a poor quality plantation. If so, there is even more to go on in terms of ecological loss because the relative importance of plantations and semi-natural habitats ought to be relatively easily demonstrated.

There is plenty of sound ecology to challenge the proposals, but perhaps the more important issue is economics? Is it really worth trashing an ancient woodland if the developer has the cost of buying anything between 3 and 10 ha to replace each hectare lost, and then has to pay for intensive management for sufficient time to create anything approaching pastiche? Someone better than me can do the economics, but it seems to me that the likely cost of creating the offset will at least mirror the cost of the ancient woodland and may indeed greatly outstrip it because woodland is relatively cheap and even low grade arable is phenomenally expensive, without adding on the cost of long-term silviculture.

Biodiversity Offsets

Recent announcements about the coalition Government's proposals for biodiversity offsetting raise some very serious questions about the degree to which policy is based on sound science. In 2005 a team of English Nature specialists investigated the issue of offsetting from the perspective of how long it might take replacement habitat to reach a condition commensurate with established semi-natural habitats. The evidence was disturbing because it highlighted a series of fundamental problems:

·         Established habitats are very largely the product of management that existed prior to deep ploughing and modern herbicides, pesticides and fertilisers. These modern practices mean that it is not possible to look at arable reversion from the same perspective as times when agriculture was less intensive.

·         All of the evidence pointed to very long timeframes for the creation of habitat that is any way analogous to existing semi-natural habitats. Apart from some wetlands, the timescales run into many decades or hundreds of years, and ancient habitats look to be extremely unlikely to be replicated. For example the plants and animals inhabiting a secondary woodland younger than 400 years are rarely, if ever, as rich as those in ancient woodlands.

·         The most critical factors involve a combination of soil chemistry, mycology, lithology and hydrology, and we know precious little about the role of bacteria in determining conditions. Soils that have been recently ploughed and fertilised with petrochemical-based fertilisers bear little resemblance to the chemical and biological conditions that existed prior to WW2, let alone those of the 17th Century, which marks the point at which woodlands start to be considered to be 'ancient'.

A paper published by this team in 2006[1] provides the foundation for the scientific debate about the likely efficacy of biodiversity offsets. Yet this, and associated evidence, seems to have been ignored, if pronouncements concerning ancient woodlands are genuinely the Government position. Suggestions that the replacement of an ancient woodland with 100 trees for each ancient tree lost is environmentally sound need to be tested scientifically. Is the Government thinking of the environment in a visual or an ecological sense? I think it must be assumed that this is a landscape rather than an ecological judgement because I cannot see how the Government's conservation advisers could conclude that there would be anything other than biodiversity loss from the destruction of ancient woodlands.

I have spent a substantial amount of time studying the insects of the British Isles and have visited a great many sites, from Shetland to Cornwall and Kent, both ancient and modern. In many cases one barely gets past the entrance before it is apparent that the site is going to be of interest or is going to be pretty mundane. One gets the feeling from the ground flora, the canopy structure (in woodlands) and the overall layout of the site. The insects are pretty telling too. Long-established sites invariably prove to be more interesting and there are good reasons for this.

At one time the countryside was far less regimented and there were uses for virtually everything. Coppiced trees provided small timber for tools, fencing or other utensils, and for firewood and charcoal. Standard trees provided structural timber and planking, whilst certain trees were deliberately pollarded to provide timbers of particular shapes for construction or shipbuilding. Grassland might have been rotated to lie fallow to improve soil productivity; elsewhere it would have provided grazing or hay. The vocabulary of the countryside reflects this diversity of use with terms such as coppice (copse), meadow and pasture forming place names. This mixed environment in which habitat was closely juxtaposed allowed plants and animals to disperse relatively readily. Today, such habitat is isolated in little pockets that we call nature reserves or protected sites.

Site protection has arisen because a part of society actually values wild places. This is particularly so for ancient woodlands, which form a central part of the countryside, both for their landscape and wildlife value. The landscape attributes are obvious, but the wildlife is rarely recognised. Much of the important wildlife (in terms of rarity and specialness) is small and relatively inconspicuous. Few visitors to the countryside other than the most ardent specialists would delight in the sight of a Duke of Burgundy Fritillary Butterfly or perhaps a Musk Beetle. It therefore follows that relatively few would miss their passing. But, many older people lament the loss of fields full of orchids or comment that butterflies seem to be much scarcer these days. In the case of my passion, numerous associates comment on the decline in insect activity at hogweed. Only today one of these friends commented that the hogweed fauna of Shropshire seemed to have declined substantially in recent years. One wonders why?

Once the basic landscape matrix has been lost, wildlife cannot move as freely. If a special site is destroyed, the special plants and animals don't just move - they die! Once they are gone, the overall numbers available to set seed, disperse spores or lay eggs to create a new generation also decline. This is why there has been an ongoing effort to arrest biodiversity loss. The first target date was 2000. That date was ambitious and the target was not achieved. A new target was set for 2010 and it too was missed. The current target is 2020 and yet in the midst of this decline, the Government determines that further ancient sites should be destroyed and replaced with pastiche. After all, nobody will notice providing the countryside has trees to create visual spectacles! If one waits for 100 years for the site to attain the characteristics needed by the plants and animals displaced when the ancient woodland was cleared, where will the colonists come from? They disappeared when the wood was bulldozed!

This saddens me greatly because we must brace ourselves for a further round of accelerated wildlife loss. There are already many parts of the country that are to all intents and purposes ecological deserts. The fens of south Lincolnshire immediately spring to mind, but there are others such as the Vale of York, the southern uplands of Scotland, much of Radnorshire and many parts of the uplands of northern England where the landscape may be spectacular but is dominated by sheepwalks! And then there are the urban habitats where the gardens are turned into concrete and wooden shrines to the motor car or the barbecue!

So, do biodiversity offsets have a place in the provisions for wildlife? The answer has to be yes, where there is small-scale cumulative loss of countryside matrix. But, there is surely a line to be drawn before more special sites are destroyed in the name of advancing the economy? If not, then nothing must be sacrosanct and we must start to consider clearing ancient villages to release land for new housing so that we don't lose the remaining agricultural land that we will need to feed coming generations - we cannot surely be anticipating using this to plant trees on!

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[1] Morris, R.K.A., Alonso, I., Kirby, K.J. & Jefferson, R., 2006. The creation of compensatory habitat - can it secure sustainable development? Journal for Nature Conservation. 14(2): 106-116.

Data from Photographs

In the course of the next six months I intend to prepare a preliminary analysis of the data gathered from websites over the last five years and to publish somewhere in the peer-reviewed literature. Odd snippets have emerged already but so far (in my article in British Wildlife and also a paper in the journal of the BENHS) but  I have not undertaken a comprehensive review. I'm not aware of any other such analyses but if anybody has come across them then do let me know.

In the past two month there has been quite a recognisable surge in data via photographers as a result of the establishment of the UK Hoverflies Facebook page. I have been amazed by its impact. There is now quite a recognisable community of photographic recorders and a steady stream of new records comes from this source. Other sources such as Ispot and Flickr remain very important, however. The ability of participants in Flickr to communicate with one another has meant that several Flickr users have now become very active recorders of hoverflies. This is fantastic.

The following graphs represent early analysis of the data but present a flavour of the nature of what is emerging from all photographic sources. So far, around 15,500 records have been assembled.

Figure 1. Numbers of identified photographs over the period 2002 to 2013. Data for 2013 are incomplete because the graph represents data to 12 October 2013. It can be expected that data for 2013 will increase substantially by the end of the year and will increase further over coming years.

The data tell an important story about the level of photographic activity. Relatively few people regularly photograph hoverflies. Eleven people (0.5% of recorders) have contributed around 20% (3,120) of all records and ~50% (7,600) of the records have been contributed by 100 people (4.2% of recorders). The data also tell us a great deal more and can be interrogated in many ways. We can say with some confidence that there is no specific tipping point where photographic recording came into its own. There has been a continuing and consistent growth in recording as shown in Figure 1. However, the development of ISpot has certainly helped (since 2009). The data collected since this point are arguably robust enough to show how this type of recording might be used to develop citizen science monitoring programmes. As a taster, Figure 2 shows how photographic activity mirrors levels of insect abundance in response to weather patterns.

Figure 2. The percentage of yearly records occurring each month over the period 2009 to 2013. This illustrates how periods of unfavourable weather affects recording effort and possibly also hoverfly abundance. For example, low numbers in July 2013 reflect a major decline in photographs posted during a period of extremely hot weather.

These notes should be seen as a highly preliminary analysis and should not be used as firm results. More work is required to make sure that duplication has been weeded out and to make sure that 2013 has been properly documented. However, they do indicate the potential of photographic data, whilst also highlighting the possible level of effort required to extract such data.

Local groups

I was in contact with a Flickr user yesterday who asked me whether I had thought of setting up a local group to improve coverage of a poorly recorded area. At the time I thought that I was probably doing as much as I could (the HRS, DF Field meetings, Training events and of course this group), but is there more that could be done?

Well, realistically, I doubt I can take on much more, but we do know that local groups can be helpful. For example Northamptonshire was an empty space on the maps until John Showers got interested and organised a local group. His group is now pretty active and Northants is now one of the better-recorded areas. So, is there scope for doing the same elsewhere? There are plenty of possibilities - what is needed is local interest.

Are there potential leaders out there who would like to stimulate improved levels of recording? Even well-recorded areas will need a new generation of recorders as our stalwarts are aging and not being replaced. Does anybody have any thoughts? There are active groups in Northants and a newly created group in Devon, together with an active group based around Preston Montford.

For those who want to get a feel for weak areas of recording, the maps on the HRS website are useful. http://www.hoverfly.org.uk/portal.php?id=2&scol=HFF0000&bkgrd=1&ecol=H0000FF&page=4

Obvious challenges are parts of Wiltshire, Buckinghamshire, South Lincs and the Fens, North Lincolnshire, Herefordshire, North and East Yorkshire, Northumbria and many parts of Scotland. Why is this? Well, I think one reason is maps tend to show where people like to go – and who wants to wander the barren wastes of the Fens? I have done this for about 10 years on and off – and it can be very boring. So at least in part, maps show where there is good habitat. But even in these areas there are little gems that the outside recorder does not know about.

It is also very noticeable that the bulk of recorders come from southern counties – why is this? Bearing in mind the historic legacy of the Workers Educational Institutes and numerous microscopy societies that abounded 100 years ago, surely this is not an area that is free of interest in wildlife recording?

What is needed is a network of 'shakers and movers'. They don't have to be experts but an ability to organise and motivate is really important. I have written on the subject from time-to-time and it does worry me that the most obvious group does not seem to be coming forward. These are recent graduates looking for a way of getting experience and making themselves stand above competitors for jobs. When I was in my formative years the local NHS was crammed full of young enthusiasts - me, Graham Collins, Jim Porter and Steve Church, Roger Hawkins, David Baldock, and led by inspirational people such as Ken Evans. That same society has no young members and I gather that meetings rarely comprise more than 3 people!

Food for thought?

Identifications from Photographs

Unfortunately, quite a lot of hoverflies are identified using characters that are difficult to depict in photos or require manipulation of the animal to get the right orientation. Thus, it is not uncommon for people to post photos that cannot be taken much further than genus, and occasionally not even that far! Most people when told that a definite ID is not possible will accept this and move on. Occasionally the person providing advice gets a torrent of abuse that they are not living in the real world and should ‘wake up to reality’. So, I thought it might be worth discussing the issues in a bit more detail. This note is a brief canter through obvious points and must not be regarded as definitive.

The first point that emerges from the photographic record is that quite a narrow spectrum of hoverflies gets photographed regularly. These are primarily the showy ones – bright colours attract attention. Many of these are perfectly doable at least to species pairs and often directly to species. There are, however, a few genera that regularly crop up and cause problems:

Cheilosia: There are some obvious species, led by C. illustrata, but accompanied by C. chrysocoma and perhaps C. grossa and C. albipila. A few regularly get photographed: C. bergenstammi, C. pagana, C. variabilis. In some cases one can be reasonably certain but in others it is more conjectural and circumstantial. Those quoted, together with occasional specimens of C. impressa are likely to be accepted as records subject to a good photo. The surprise is C. caerulescens which is often readily recognisable and has a certain jizz about it that I cannot describe. It is not infrequently photographed in gardens but I would be at a loss to say quite how/why I would recognise this apart from the facial profile and when the wing shade is obvious – it is considerably hairier in some places but cannot be described. These apart, I fear the majority cannot be done although one might have a good idea of what something is likely to be. I guess the difference between me and some recorders is that I am immediately thinking of what happens to the record and how this affects data reliability.

Epistrophe/Eupeodes/Melangyna/Parasyrphus: A few are readily identifiable such as E. eligans and E. grossulariae. Many firm IDs rely on micro characters such as wing microtrichia or hair colours that are generally poorly depicted in photos. Thus, the degree to which an ID can be given is often directly proportional to the quality of the photo. I’ve seen some fantastic stacked shots that make ID quite possible for many species, but not all features of importance are readily depicted on a live photo because wings may cover them or they may be on the underside of the animal.

Eumerus: these are generally not possible because the critical characters on the hind femur are obscured unless the animal is at least unconscious and inverted.  It has been further complicated because a new species has been added to the list - Eumerus sogdianus, which is very similar to E. strigatus and can only be separated on genital characters.

Melanostoma: At certain angles, male M. mellinum and M. scalare can be separated with modest confidence, provided they are from lowland locations. Even so, there are some where the elongate abdomen of M. scalare is not as pronounced as illustrations suggest. It is highly possible that a further species lurks here and several specialists have also suggested that there is a much bigger complex. In females, the dusting on the frons (not withstanding Species A and M. dubium) is distinctive provided one is looking directly down on the head. The problem is that extent of dusting is frightfully variable, with lots of intermediates.

Platycheirus: A few are eminently doable such as P. granditarsus, P. rosarum and perhaps P. manicatus. So too are many, but by no means all, P. albimanus. Thereafter, life becomes complicated and those males where the pits on the underside of the front tarsi are key characters are not generally doable because the animal is standing on the character concerned! In males, greater chances of ID are possible if the front legs and especially the tarsi are sharply depicted. Females are much trickier, and in general I would hesitate to tackle many of the yellow ones. Now, in reality, many of these segregate themselves because relatively few are photographed: most occur low in wetland vegetation and only a few will bask on leaves and flowers sufficiently regularly to get noticed. Also, they are small and therefore less likely to be noticed.

Pipizini: A very tricky tribe, although the odd specimen is doable. Pipiza austriaca is occasionally obvious and so too is Pipizella viduata at some profile angles where the antennae are well illustrated. These apart, there is little to go on without micro characters and genitalia examination for some.

Sphaerophoria: Lots of people put names to females, and although there are continental keys they are not reliable. From personal experience I have found them to be extremely tricky with preserved specimens that can be highly magnified, so I fear there is a minefield if one is tackling them from a blurry photo or even a reasonably sharp one. The resolution is rarely likely to be adequate. In males, apart from S. scripta, S. rueppellii and S. loewi, there are no good external characters and one is dependent upon the structures within the genital capsule. Male Sphaerophoria are bashful and hide these bits, so ID from a photo is pretty well impossible.

Syrphus: We see hundreds of shots of Syrphus and many relative novices try to put a name to specimens. It is not unusual to see names being allocated on the colour of bands or other characters that are not used in the keys. In my experience, it is rarely possible to do males, although occasionally one sees a nice shot of S. torvus in which the eye hairs are visible. In females, S. ribesii can be separated if the hind femora are fully visible (not possible from above); but only if one assumes that S. rectus does not occur in the UK. The jury is out on that one and probably we won’t know until there is DNA analysis of European and North American specimens.

There are a few other challenges, but the above is enough to get started with. The key point that emerges out of this is that the better quality the photo is, the greater the likelihood of getting a firm ID. In a recent debate it was pointed out to me that I should be providing advice on the angles that people should be taking shots from. This really is not practical – the angles depend upon a thorough knowledge of the insects in question and therefore until the photographer has gained an understanding of the genera and what they are photographing they will almost inevitably miss the key character. Thus, it seems to me that the best advice one can give the novice is to try to get to know the genera first. This is the approach we take in our training courses – pretty much the first half day ID session focuses on embedding the use of the key to get to Tribes. Thereafter greater refinement slots into place.

After that, the critical issue is to get confirmation of tentative Ids. Please don’t expect a line by line explanation for every photo. Those of us that do try to help often put in spend several hours a day. We are happy to help where we can, but there are limits to the time that can be spent explaining in full on several occasions a day why a photo cannot be taken further than a genus.

A cold spring

The news today reported that this was the coldest spring for 50 years! Well, the data from the internet confirms this - numbers of photographs accompanied by locality  posted this year are well down on both the last two years and in April they barely reached the level of 2010.

The following to graphs illustrate this. However, it must also be noted that the numbers of photographs with data posted in May exceeded any previous year. It is also quite surprising that good numbers of records were generated last Saturday, but the numbers for Sunday and Monday were well down on what might be expected for a nice sunny Bank Holiday.

Numbers of photographs posted with location data 2004 to 2013 for the period January to April. Each bar represents the cumulative numbers for the period.

Numbers of photographs posted with location data 2004 to 2013 for the period January to May. Each bar represents the cumulative numbers for the period.

These data suggest that interest in photo recording continues to grow. I am starting to think there might be scope in developing a more detailed photo-recording initiative based on iSPOT or similar technology. Scanning websites also makes me think we need a team of entomologists extracting data for all taxa. The numbers of moths and butterflies posted is amazing and there are good numbers of beetles and shield bugs.

Disrupted services

I realise that it is a very long while since I last posted anything. There have been various distractions; not least the job of send out large numbers of WILDGuides! We are not quite sure how many have actually been sold world-wide, but we think it is in the order of 1800 copies. Stuart and I have sold (on behalf of Dipterists Forum) around 200 copies. As I've previously mentioned, the proceeds are going to Dipterists Forum and we hope that they will be used to support training programmes for new dipterists.

There are several pieces of news to relay.

1. A new approach to keys

Stuart and I are working on a new key to Platycheirus. Although based on the key in Stubbs & Falk, we are planning that it should be extensively illustrated with photographs and populated with maps and phenology diagrams as well as species descriptions. It is the first stage in planning for a new version of Stubbs and Falk. However, unlike previous approaches we have concluded that a new format is needed to improve the presentation of the keys (lots of people have trouble with following the right couplets). We also want to re-organise and re-write the species descriptions to incorporate new learning and experience from running training courses. This key will hopefully come out as a Dipterists Forum publication in the autumn. My guess is that it will be 60-80 pages in length - I've completely re-written the species descriptions and Stuart has a draft layout for the key. All we now need to do is to put it together and chase down specimens of a few species to photograph.

2. Species on the move

Yesterday I was alerted to a photo of Rhingia rostrata from Cumbria. The locality is within the known hot spot around Grange-over-Sands whose climate is rather different to the rest of Cumbria. Given that it has moved this far - a massive leap from the latitude of South Yorkshire - there is the possibility of a wider scatter of new records this year!

Some while ago I was contacted by Chris Webster who takes fantastic hoverfly photos. He had a Syrphus-like species that was puzzling him. It turned out to be S. nitidifrons. The photo can be seen on Steve Falk's website http://www.flickr.com/photos/63075200@N07/8485678619/ .

3. Training

Stuart and I ran a weekend course at Cardiff Museum in April that was a departure from our traditional introductory course. This one was an 'improvers' course that focused on Platycheirus and Cheilosia. It was very successful and we hope that we will be able to run a few more in coming years. What is really nice is to see old friends who attended past courses and continue to record hoverflies.