Species distribution mapping and its insights on the self-assembly of wild nature
On our way to the Northumbrian coastline three weeks ago for more low-tide walking, we made a long-planned stop-off at Barters Books in Alnwick, a second-hand bookshop stuffed into a Victorian railway station (1). As well as hoping to pick up some science fiction novels for bedtime reading, I always look for interesting older books that may shed light on earlier thinking on the threats to nature and its restoration (eg. The Prospect for Wildlife by Bruce Campbell (2) Before Nature Dies by Jean Dorst (3)). I was hoping to pick up a copy of Clive Ponting’s book about the green history of the world, as I had hesitated over buying it 20 years ago when I saw it remaindered, and have regretted it ever since (4). A couple of years ago, I made use of information excerpted from his book on the colonisation of Easter Island (5). It was in a lecture I gave on humans being an exceptional species, and what threat that posed to wilderness, questioning whether the human species, by its very behaviour, could be regarded as part of nature (6). The lesson of Easter Island was a cautionary tale in that it showed that from an initial colonisation 1,500 years ago by 20-30 Polynesians, the population burgeoned to 7,000 by 1550, but in the process stripped the island of its natural resources. Deforestation in particular accelerated due to meeting the need not only for houses and firewood, but in the ritual and ceremonial culture that developed on the island, and which consumed many trees in moving and erecting stone monuments for ancestor worship. Thus a complex society had disintegrated, trapped on an island of environmental limitations and pressure – “unable to escape the consequences of their self-inflicted, environmental collapse”(5).
Watsonian vice counties and the spatial distribution of plants
I didn’t find Ponting’s book, and the science-fiction section lacked the kind of space travel novels I like. However, I was astonished to come across one of Hewett Watson’s books on the phytogeography (plant geography) of Britain. Watson (1804-1881) was a Yorkshire-born botanical geographer who, during the mid-nineteenth century, used his own and other records for the presence of plant species in Britain to devise a system to indicate their distinctive range by assignment into six zones based on altitude, and into eighteen Provinces based on river drainage, and which were published in a four volume series entitled Cybele Britannica (7). When I first wrote about this, I noted that he had subsequently published a couple of volumes of Topographical Botany that were a comprehensive listing of individual species in county records, but without reference to the altitudinal elements (8). What I was holding in my hands was a revised edition of that Topographical Botany from 1883 that Watson had intended to publish, but which had to be compiled from his notes, as he died before he could complete it (9).
I did not explain originally that those listings in Topographical Botany were based on much smaller geographical areas devised by Watson through subdividing the Provinces into 38 Sub-provinces, which he then divided further into 112 vice-counties of roughly equal size, and which he explained in the third volume of Cybele Britannica – “In the latter more numerous sections, some of the sub-provinces exactly correspond with the smaller provinces, and many of the vice-counties are identical with the smaller counties ; the rule having been to subdivide only the larger provinces and counties” (10). They thus provided a finer scale spatial distribution of species listing across Britain than just the 18 provinces. I have noted before that Irish naturalist Robert Praeger (1865-1953) was inspired by Watson’s work, and set out walking Ireland at weekends in 1896 to complete a detailed geographical analysis of Ireland's plants, based on Watson’s approach of county divisions (8). What I hadn’t realised was that he had brought the vice county system to Ireland when he created 40 botanical divisions of nearly equal size, some with similar boundaries to existing counties, and similar in area to Watsons 112 vice counties (11,12). Praeger described the climate and soils of Ireland, discussed the topographical divisions and their vegetation, and gave the typical vegetation based on soil and moisture – he also gave overall maps of Ireland with the botanical divisions shown overlaying its geology and altitude, but he listed species in those botanical divisions in the same way that Watson did in his Topographical Botany, without reference to the specific conditions within the botanical divisions that each species existed. The significance of these vice-counties and botanical divisions (see the vice-counties in Britain on a digital map (13)) is that they would become the standard basis of biological recording and other scientific data-gathering, more of which later.
Another fascinating find at Barters Books was a copy of the first Atlas of British Flora published in 1962 on behalf of the Botanical Society of Britain and Ireland (BSBI) (14). In contrast to the vice-county lists of Watson, this contains dot-distribution maps of plant species in Britain based on their presence within the 10km squares of the Ordinance Survey’s National Grid System, each grid square containing 100 possible dot locations (10x10)(14,15). I became familiar with these dot maps some years ago from The West Yorkshire Plant Atlas published by the local authority for which I was working in rural policy (16). The map for a common species like rosebay willowherb (Chamaenerion angustifolium) was just covered with dots, but if you looked carefully, you could see blank spots on the map that correlated with the high moors of the upland areas to the western edge of the region, and where it made sense that you were unlikely to see it. Common nettle (Urtica doica) showed the same distribution. Plants that were less common, or had much stricter habitat requirements, showed an even greater spatial correlation of their dot maps with the varying altitudinal, edaphic and hydrologic conditions across the region. Thus white bryony (Bryonia dioica) was almost exclusively distributed on the eastern edge of the region where a belt of Magnesian limestone runs up and down. In contrast, crowberry (Empterum nigrum) showed an almost exclusively western distribution that correlated with the acidic conditions of the high moors. A number of species showed clear distributions that tracked marshy areas, canals, river and streamsides in the region, such as water plantain (Alisima plantago-aquatica) trifid bur-marigold (Bidens tripartita) marsh woundwort (Stachys palustris) hemlock water-dropwort (Oenanthe corcata) white willow (Salix alba) and reed sweetgrass (Glyceria maxima) with the mapping for flowering rush (Butomus umbellatus) and arrowhead (Sagittaria sagittifolia) almost exclusively tracking the course of the Leeds-Liverpool canal.
As with so many other systems of displaying spatial distribution today, paper maps have given way to interactive digital maps for species distribution. The one I use the most is the National Biodiversity Network (NBN) Atlas (formerly the NBN Gateway) where a search can be made for the spatial distribution of a specific species (17). In the case of wildflowers, I also use the BSBI’s Online Atlas of the British and Irish Flora that has dot maps and some lifeform and habitat information (18) but in more portable form, I have Simon Harrap’s field guide that includes a thumbnail dot map for each wildflower species (19) and I still keep close my copy of the first edition of Alastair Fitters guide to wild flowers (20).
Finding a sea squirt
The tentativeness was there again, and I left the atlas behind as we carried on up to Seahouses for some walking of the low-tide coast between Beadnell and Berwick. Although the tides were moving into neaps, when there is least difference between high and low water (21) we were still able to get far enough out on rock terraces at low tide to see some wonderful seaweeds, and watch the sea birds and waves crashing. The maritime fauna is less diverse compared to other places we go, two types of sea anemone in the beadlet and dahlia, compared to six on the Pembrokeshire coast (22) but there are breadcrumb sponges, and this time - at last - I found an orange ascidian (Botrylloides leachi (23)) a sea squirt that forms colonies within a gel tunic. I had to crawl into a sandstone tunnel at low tide at Braidcarr Point to photograph this sea squirt encrusting the dark dampness of its roof, the tunnel having been made in this soft rock from the daily grinding and wearing away with each tide (24). The sponges on this sandstone tend to grow in the shade of a runnel in the rock (25) whereas the squirts and sponges on the Pembrokeshire coast are on the dark dampness of rock overhangs (22). As I have noted before, we collect uncommon shells at the high tide mark along this coast (22) and it’s no surprise that we found cowries (Trivia monarcha) as they feed on ascidians like this orange one, and slit limpets (Emarginula fissure) that feed on sponges (26). It would be better to have seen these molluscs alive and in habitat, as we have in Pembrokeshire for the cowrie (22) but there is always the satisfaction of recognising the links in marine trophic ecology. We got drenched on our last morning there, but we weren't going to waste it.
On a day sat out amongst the rock pools, thong weed and other deeper water seaweeds at the edge of low tide at Snook Point (see the photos of this lower shore zone in (27)) we pondered on the fact that we never see anyone else in these low tide locations. Of course, it would spoil it if it was swamped with people, but why aren’t others at least inquisitive about what they might find at this sub-tidal fringe? Anyway, we tried to make a list of the people we knew that would probably share our interest. It was a very short list. Why is this so?
The beautiful seaweeds revealed in the lower zones of the inter-tidal range had been our first draw to these rocky coasts at low tide (25, 28) and then it was the rocky Pembrokeshire coast where we first found sea squirts, the greater variety of the carnivorous sea anemones, and of the carnivorous starfish, as well as a carnivorous shellfish in the cowrie, all adding more pieces to the pattern of marine trophic ecology (22,29). Apart from the sea urchin (Echinus esculentus) and sea hare (Aplysia punctate) that we found out on the low tide rock ledges of the North Yorkshire coast, and the starfish (Asterias rubens) at Cocklawburn beach just below Berwick on the Northumberland coast (25 ) the orange sea squirt we found this time at Braidcarr Point was a first advance into that greater diversity. Partly it’s an issue of intentionally looking for it, now that we have the experience from the Pembrokeshire coast, but there is less abundance of damp and shady rock-overhang habitat on the Northumberland and North Yorkshire coasts compared to the Pembrokeshire coast. We regretted not checking the NBN Atlas for the presence of a few of these species before we went to Northumberland, as the distribution mapping may just show a seemingly lower diversity of these lower tidal zone species.
Other sea squirts to find
I thought about that plant Atlas while we were out walking, and how useful distribution maps are in locating the presence of species, but also interesting for the patterns of distribution they reveal related to habitat (see above). With this in my head, we dropped into Alnwick on the way home and bought the plant atlas. The first thing I did, though, when I got home, was to check the distribution of a couple of sea squirts (30,31) dahlia sea anemone (32) breadcrumb sponge (33) and spotted cowrie (34) on the NBN atlas to see if they appeared on all three of the low-tide coastlines we walk. This was generally the case and, apart from some discontinuities around the eastern coast of Scotland, and some parts of eastern England, these marine species appeared present for the most part around all of Britain’s coastline, albeit the precision for a particular location at large scale was not great. This was not always resolved by zooming in, but it did show a greater occurrence of dots for each of those species around the Pembrokeshire coastline. This was elucidated by clicking on the records section of each species where the number of occurrence records for the Pembrokeshire vice-county were invariably higher than in any other, and certainly higher for the number of records for the vice-counties covering North Yorkshire and Northumberland (see for orange sea squirt (35)). I’m not sure this is necessarily an indication of abundance, and it may reflect the influence of people like John Barrett in fostering a greater inquisitiveness in marine recording on the Pembrokeshire coast (29).
Then I had a breakthrough in encouraging me that we would have hope of finding all these species on the low tide coast at Seahouses, as well as Pembrokeshire. There is a search facility on the NBN Atlas for a specific location, giving all its species records in areas of decreasing radius from 10 to 1km. This proved to be a goldmine of information when I put in the Ordinance Survey map coordinates for a point just off the rocky seashore between Southend Rock and Snook Point at Seahouses (36). At a radius of 1km, a total of 419 species was returned, broken down into species groups based on animals, plants, fungi, algae etc. and with their common name as well where available. There was also a satellite photo of the area showing the target circle superimposed, and then a series of dots within the circle showing the location of the records of occurrence, both on land and sea. I was only interested in marine species, and in clicking on algae, a list of 59 species appeared, the dot locations on land disappeared, leaving only those in the marine territory. Amongst the list were various seaweeds that we have seen in this location, such as wracks, gutweed, coral weed, red rags, pepper dulse, thong weed, dulse, dabberlocks, cladophora, and kelps. As you would expect, selecting molluscs brought up a list that included spotted cowrie. However, I had to select the largest group – animals – to find listed both sea squirts, common starfish, the beadlet and dahlia anemones, and breadcrumb sponge. On these listings, we thus have a hope to find star ascidian (Botryllus schlosseri) there, as well as other species we have seen in Pembrokeshire, such as snakelocks anemone (and thus three at Seahouses compared to the six in Pembrokeshire) purse sponge, cushion star, and another orange sea squirt (Aplidium nordmanni) (37). The challenge is now to identify the type of damp and shady habitat niche that these species occupy.
By some sign, or spot of colour
I approached the plant Atlas with a different eye. It is a book that I am more likely to dip into occasionally, rather than delve deeply, as it contains 1,700 dot maps, four to a page, showing black dots for records since 1930 and open circles for older records (14). In its own way, it is as significant a book as any of Hewett Watson’s, because it was the first large scale compilation of dot-distribution maps for flowering plants and ferns of Britain and Ireland. The early history on the mapping of plant distribution given in the Introduction gives due respect to Watson, but also notes that he had envisioned dot maps in 1836 – “by some sign, or spot of colour” (see pg 19 (38)). In looking for where that quote appeared, I came across two earlier works of Watson, both on the geographical distribution of British plants, which trace the evolution of his thoughts on how he could approach documenting that distribution (39,40). It was, however, German geographical botanist Hermann Hoffmann (1819-91) who knew of Watson’s work, that is credited with producing the first regional dot maps for the distribution of wildflowers. Hoffmann had made the connection in 1860 that a couple of wildflowers, selfheal (Prunella grandiflora) and German pink (Dianthys carthusianorum) were always found growing in calcareous areas in the neighbourhood of Giessen and Kissingen in Germany (41). In a later publication from 1879, Hoffmann grids up the Middle Rhine Region, and then gives a series of grid maps showing the presence or absence of plant species in the grid squares (42). At the end of the article, Hoffmann shows dot maps of the specific location of the records of occurrence for a few species, such as danewort (Sambucus ebulus) an herbaceous species of elder, tuberous vetchling (Lathyrus tuberosus) a perennial climber resembling a sweet pea, and holly (Ilex aquifolium) (see No. 3-5 (42)). It would not be until 1936, a century after Watson suggested it, that the first dot distribution map of a plant species in Britain was published. This was by British botanist Ronald Good (1896-1992) who mapped the distribution of Lizard Orchid (Himantoglossum hircinum) and you can see for yourself how limited this distribution is, the orchid being confined mostly to SE England and seemingly spatially correlating with chalk soils (see Figs, 2-5 in (43))
It is that edaphic aspect of habitat preference that is always a feature of phytogeography, along with topography and climate, and which is strengthened by the Atlas containing a wallet at the back in which there are six transparent map overlay sheets. Each sheet has two maps of Britain and Ireland with a different theme, such as those factors that would have a bearing on plant distribution - altitude, rivers, chalk and limestone geology, rainfall, humidity, temperature at different months of the year – as well maps showing the vice-counties, all of the grid squares, and those grid squares with relatively few records of species occurrence. The latter doesn’t necessarily imply a lack of species in those areas, just that there haven’t been much recording effort there. Usefully, also in the Introduction is some explanation of how the data on the overlay transparencies can be used in interpreting distribution patterns, since all these maps are the same size as the dot distribution maps, and so can be laid over the dot maps to see whether the distribution of a species correlates with one of the themes.
Altitude maps can show the tolerances of mountain plants, such as a highland cudweed (Gnaphallium norvegicum)(44) confined to the highest mountains, to starry saxifrage (Saxifraga stellaris)(45) found at lower but still significant altitudes. For the overlay that is indicative of lime loving species, the example given is kidney vetch (Anthyllis vulneraria) (46) which is one of our most favourite coastal flowers, as its yellow flowers cascade down cliffs, the dot map showing it circumnavigating the coast of Britain. The soil there is often free-draining and neutral. However, to our initial surprise, we have also seen it growing in the limestone dales in Yorkshire, and it appears from the dot map that inland kidney vetch grows predominantly in areas of chalk and limestone. Conversely, the dot map for bell heather (Erica cinerea)(47) shows that it avoids the chalk and limestone areas, leaving the map free of dots there. As you may imagine, the examples of distribution based on temperatures and rainfall are extensive, and indicative of factors like northern and southern limits, as well as east-west distributions, based on different tolerances to summer and winter temperatures, the respective bands or zones of temperature (isotherms) run horizontally (N-S) across Britain in summer with higher temperatures in the south, but vertically (E-W) during winter with higher temperatures in the west. One example for temperature dependency given is the white starflowers of chickweed-wintergreen (Trientalis europaea) that I have seen in woodland next to Brimham Rocks near Pateley Bridge in N. Yorkshire. It requires low temperatures for its seed to germinate, and therefore it is not surprising that my sighting is about as far south as this wildflower gets, with its predominant distribution being in the Highlands of Scotland (48). An example of a plant better suited to the drier conditions of eastern Britain is Spanish catchfly (Silene otitis)(49). The humidity data is also linked to dryness, but more interesting for me is it being a factor in hyper-oceanicity near coastlines, and how this gives rise to woodlands on the western coasts of Scotland and Ireland astonishingly rich in lichens, mosses and liverworts (50-51).
It is tempting to run through all the distinctive dot distribution maps I have already found in the Atlas, such as sea holly (Eryngium maritimum)(52) sea beet (Beta vulgaris subsp. maritima)(53) and sea campion (Silene uniflora)(54) that all hug the coastline, and the native distribution of Scots pine (Pinus sylvestris)(55) shown exclusively in the Highlands of Scotland. As the atlas also covers Ireland, I also looked to see if it would display the disparity in species between there and Britain, with a number of our native species being absent from Ireland. This was due to the return of species from the east after the last glaciation being interrupted by sea level rise and the consequent loss of the land bridge not only between Britain and continental Europe, but also between Britain and Ireland (50). A couple of these species missing from Ireland are amongst my favourite woodland plants: herb paris (Paris quadrifolia)(51) and moschatel (Adoxa moschatellina)(52). The distribution maps also demonstrate the converse in that there are native species in Ireland that are not in our flora, the Lusitanian species for which there is no conclusive explanation for their presence as natives only in Ireland, Spain and Portugal (50). I’ve seen some of these species in Ireland, including Irish spurge (Euphorbia hyberna)(53) and large-flowered butterwort (Pinguicula grandiflora)(54) and their dots maps in the Atlas confirm a south-western presence in Ireland, and absence in Britain.
The compilers, after finishing the Atlas, had intended to write a book about the phytogeography of the British flora (55). However, the increasing concern for the parlous state of conservation of some species in the 1960s led one of the authors instead to write the first British Red Data Book in 1977 where flowering species were ranked as to their vulnerability: rare species were defined as those that occurred in 15 or fewer grid squares; scarce were those in 16-100 grid squares; and declining species were those with occurrences in less grid squares after 1960 than before (55,56). The importance of this Red Book listing is that the presence of both rare and scarce species was, and still is, a criteria used for selecting Sites of Special Scientific Interest (see section 5.7.3 (57)). It is a pity, but understandable, that the Red Book took priority over phytogeography, because I made important use of a study that identified the major phytogeograhical zones of Scotland in an option paper I wrote for the John Muir Trust on the protection of wild land in Scotland (58,59) and I have yet to find comparable studies for the rest of Britain.
The homogenisation of edaphic conditions obscuring distinctive plant distributions
A New Atlas of the British and Irish Flora was published in 2002 that presented an up-to-date summary of the range of 2,412 British and Irish flowering plants (60). This update was valuable in that it demonstrated the large number of changes that had taken place in the intervening 20 years in the range and frequency of many species (61). It showed an increase in species with a Mediterranean distribution, such as spotted medick (Medicago arabica)(62) and wild leek (Allium ampeloprasum)(63) and a decrease in species with a northerly global distribution, such as the moorland species of bell heather (Erica cinerea)(47) and hare's-tail cottongrass (Eriophorum vaginatum)(64). There was a high relative increase in all English regions in non-native species introduced in recent times (neophytes) such as butterfly-bush (Buddljia davidii)(65) a native of China, and American willowherb (Epilobium ciliatum)(66). Perhaps more disturbing was an increase in species that thrive in nutrient-rich soil, and a decline in those that prefer low-nutrient habitats, as well as a decrease of species of low or high pH, compared to those that favour neutral conditions (61). Some explanation is given for these changes, such as increasing levels of nutrients, habitat loss caused by intensive agricultural practices and deforestation, and the spread of plants from gardens.
There is to be another updated Atlas in 2020 (67) and which I expect will show the continuing homogenisation of edaphic conditions towards higher fertility and more neutral pH in our landscapes, so that we increasingly lose the distinctive plant distributions that we derive from low fertility and variations in pH. I view those distinctive distributions as a signal of the capability for a diverse, natural self-assembly of our wild nature, and what vegetation our landscapes would clothe itself in the absence of our interference. It is the basis, along with climate and topography, of projections of natural vegetation that I have written about previously (8) and opens up potential and possibility, as averse to the dead hand of that homogenisation. It seemed fitting to me that I dwelt on this indicative aspect of the plant Atlas while walking the inter-tidal range on the Northumbrian coastline, because it is there that I see the most distinctive influence in wild nature in Britain for the distribution and self-assembly of species - the stark contrast in habitat conditions between the rise and fall of the tide in terms of light, desiccation, wave motion etc. and which gives rise to a marked zonation in the seaweeds, but also in the other marine flora and fauna. What I also see there is the high trophic occupancy, the marine trophic ecology of carnivores, herbivores and plant growth.
The distinctive distributions in the plant Atlas give no clue to that trophic occupancy, but they are the essential framework to a terrestrial trophic ecology. We need to see the distinctive natural vegetation that develops in reaction to the varying soils, hydrology, topography and climate, and which has been lost from view in our highly modified landscapes. Having to row back centuries of absolute control exerted over our countryside, and consequent persecution and extirpation of species, is a must if we are to have a high aspiration for natural vegetation (68). Scale is important for this aspiration in terms of the location having the resilience in being able to overcome disease, as well as natural disturbances such as wind and hydrology, through allowing the fullest range of natural processes to take place. A large size is thus also important in terms of achieving sufficient space to accommodate a number of home ranges of the large carnivores, but it should also be seen as being able to support viable populations of all indigenous species associated within the biophysical variation of the location. To forestall criticism that it will be wall to wall high canopy forest, an altitudinal perspective covering the bio-geographic spectrum from coastline to high hills will hopefully encompass a range of climatic and edaphic factors, moisture, soil, aspect, disturbance etc that will give rise to a matrix of varying, self-perpetuating closed and open habitat. It’s about a tree-line woodland at the true extent of its altitudinal range, and of course bog woodland in the uplands as well. I would hope to see coastal cliff assemblages of vegetation that alter the further inland you go as the forces of coastal exposure recede, and large scale wetlands where the carr woodlands have their characteristic untidiness and trees fall over from the lack of purchase.
This may seem the same imperative repeated over and over again, but if we are serious about our wild heritage, then there has to be space for this in Britain (8,69). Ecological enrichment to the point of self-assembly of species in self-regulating and spontaneously self-perpetuating processes will be measured in multiple decades to centuries, and so it would be fascinating to be around to see the dot distribution maps of plants for a location enriched like this in the new Atlas of 2217.
Mark Fisher 15 October 2017
(1) The Bookshop, Barter Books, Alnwick
(2) The most unnatural conservation policy possible, Self-willed land July 2010
(3) When nature dies - the impact of the human species, Self-willed land July 2015
(4) Ponting, C. (1991) A Green History of the World: The Environment and the Collapse of Great Civilizations. Sinclair-Stevenson
(5) Ponting, C. (1991) The Lessons of Easter Island, excerpt from Ch. I, A Green History of the World: The Environment and the Collapse of Great Civilizations
(6) Fisher, M. (2015) Humans as exceptional beings and the threat to wilderness, WRi 8 October 2015
(7) Watson, Hewett Cottrell, Internet Archive
(8) The natural vegetation of England, Self-willed land August 2014
(9) Watson, H.C. (1883) Topographical botany: being local and personal records towards shewing the distribution of British plants traced through the 112 counties and vice-counties of England, Wales, and Scotland. London, B. Quaritch
(10) Watson, H.C. (1852) Cybele Britannica: or British Plants and their geographical relations Vol. III. London: Longman & Co
(11) Praeger, R.L. (1901) Irish Topographical Botany. Proceedings of the Royal. Irish Academy, 7:1-410
(12) Praeger’s map of Ireland showing his botanical divisions
(13) Grid reference to vice-county, Lincolnshire Beetles
(14) Perring F.H. & Walters S.M., comps & eds (1962) Atlas of the British flora, Botanical Society of Britain and Ireland. London: Thomas Nelson & Sons
(14) Using the National Grid, A Beginners Guide to Grid References, Ordnance Survey
(15) Distribution maps of plants, Maps and Data, BSBI
(16) Lavin, J.C. & Wilmore G.T.D. (1994) The West Yorkshire Plant Atlas. Bradford, City of Bradford Metropolitan Council, 1994
(17) National Biodiversity Network Atlas
(18) Online Atlas of the British and Irish flora, British flora, Botanical Society & Biological Records Centre
(19) Harrap. S. (2013) Harrap's Wild Flowers. A & C Black
(20) Fitter, A. (1987) Wild Flowers of Britain and North West Europe (New Generation Guides) Collins; 1st edition
(21) Real-time/near real-time data display for North Shields: 25-29 September 2017. National Tidal and Sea Level Facility, National Oceanography Centre
(22) Discriminating between the wild and not wild, Self-willed land August 2017
(23) Botrylloides leachi, Sea Squirts, Encyclopedia of Marine Life of Britain and Ireland
(24) Mike Hosken, SEAHOUSES ROCK, "Colour Supplement" Seahouses Community Website
(25) Patterns and disconnections in nature, Self-willed land August 2016
(26) Slit limpet (Emarginula fissura) Marine Life Information Network
(27) Mike Hosken, FORESHORE ZONATION AT SNOOK POINT, "Colour Supplement" Seahouses Community Website
(28) Unfinished business on rewilding - a comparison between Rewilding Britain and Rewilding Europe, Self-willed land May 2016
(29) Rumination, mindfulness and Awe Walks, Self-willed land June 2017
(30) Botrylloides leachii, NBN Atlas
(31) Star Ascidian, Botryllus schlosseri, NBN Atlas
(32) Dahlia Anemone, Urticina feline, NBN Atlas
(33) Breadcrumb Sponge, Halichondria (Halichondria) panacea, NBN Atlas
(34) Spotted Cowrie, Trivia monacha, NBN Atlas
(35) Botrylloides leachii, Charts showing breakdown of occurrence records (2,073 Records) By Watsonian Vice County, NBN Atlas
(36) Seahouses. Map Reference NU228319, Explore Your Area, NBN Atlas
(37) Aplidium nordmanni - A Sea squirt, APHOTOMARINE
(38) Watson, H. (1836) Art. V. Observations on the Construction of Maps for illustrating the Distribution of Plants, with Reference to the Communication of Mr. Hinds on the same Subject. (Vol. VIII. p. 498.). Magazine of natural history and journal of zoology, botany, mineralogy, geology and meteorology Vol IX: 17-21
(39) Watson, H.C. (1832) Outlines of the geographical distribution of British plants : belonging to the division of vasculares or cotyledones, Edinburgh : Printed for private distribution
(40) Watson, H.C. (1835) Remarks on the geographical distribution of British plants : chiefly in connection with latitude, elevation, and climate. London : Printed for Longman, Rees, Orme, Brown, Green, and Longman
(41) Ihne, E. & Schroeter, J.(1892) Hermann Hoffmann. Berichte der Deutschen Botanische Gesellschaft 10: 11–27
(42) Hoffmann, H. (1879): Nachträge zur Flora des Mittelrhein-Gebietes. Berichten der Oberhessischen Gesellschaft für Natur- u. Heilkunde 18: 1-48
(43) Good, R. (1936) On the distribution of Lizard Orchid (Himantoglossum hircinum). New Phytologist, 35: 142 - 170.
(44) Gnaphalium norvegicum, Online Atlas of the British and Irish flora, British flora, Botanical Society & Biological Records Centre
(45) Saxifraga stellaris, Online Atlas of the British and Irish flora, British flora, Botanical Society & Biological Records Centre
(46) Anthyllis vulneraria, Online Atlas of the British and Irish flora, British flora, Botanical Society & Biological Records Centre
(47) Erica cinerea, Online Atlas of the British and Irish flora, British flora, Botanical Society & Biological Records Centre
(48) Trientalis europaea, Online Atlas of the British and Irish flora, British flora, Botanical Society & Biological Records Centre
(49) Silene otitis, Online Atlas of the British and Irish flora, British flora, Botanical Society & Biological Records Centre
(50) Wild Nephin – future natural wilderness in Ireland, Self-willed land April 2013
(51) Coastal temperate rainforest - in Britain?!, Self-willed land June 2015
(52) Eryngium maritimum, Online Atlas of the British and Irish flora, British flora, Botanical Society & Biological Records Centre
(53) Beta vulgaris subsp. maritima, Online Atlas of the British and Irish flora, British flora, Botanical Society & Biological Records Centre
(54) Silene uniflora, Online Atlas of the British and Irish flora, British flora, Botanical Society & Biological Records Centre
(55) Caledonian pinewoods, Trees for Life
(51) Paris quadrifolia, Online Atlas of the British and Irish flora, British flora, Botanical Society & Biological Records Centre
(52) Adoxa moschatellina, Online Atlas of the
British and Irish flora, British flora, Botanical Society & Biological Records
(53) Euphorbia hyberna, Online Atlas of the British and Irish flora, British flora, Botanical Society & Biological Records Centre
(54) Pinguicula grandiflora, Online Atlas of the British and Irish flora, British flora, Botanical Society & Biological Records Centre
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