Flora of Borrego Badlands Area
Summary of Checklist and Species Not Found
This checklist is a start at a flora of the Borrego Badlands Area, from vouchers and field surveys.
The floristic area denoted as the Borrego Badlands is delineated by the red rectangle in the following map:
The western area includes all of what is marked as the Borrego Badlands on the topographic map, plus additional non-badland area. This floristic area is extended to the east to the Imperial County Line since that eastern area is similar in many respects to the Badlands. The northern boundary is arbitrarily set along Highway S22 for convenience and clarity. The southern boundary is set to exclude the Borrego Sink Wash, San Felipe Creek, and the Ocotillo Wells Off-Road Vehicle Area.
Note that this area includes a majority of non-badlands area.
The name badlands refers to a intricately-sculptured landscape in easily-eroded rock, characterized by steep slopes, minimal vegetation, lack of a substantial regolith, and high drainage density. If this flora were confined to just the actual badland area, it would be much shorter, since only a small number of species can tolerate the lack of normal soil on the surface, and the extreme alkalinity of the exposed sedimentary rock. Most of the actual badlands have no vegetation at all on them.
Vouchers were searched and examined on at least three different dates, so the following is a bit more complicated than it would be from a single voucher search.
The vouchers come from a search on 16 December 2007 of the Consortium of California Herbaria, and a search of the San Diego Plant Atlas and Herbarium records, and a later search for vouchers with coordinates on 30 November 2013, for 33.24 to 33.30° N. latitude and -116.27 to -116.19° E. longitude. Vouchers outside the target area were tossed.
More information on the on 16 December 2007 voucher search:
The Consortium records were searched for San Diego County specimens that contained the words badland or Font in the locality. Redundant vouchers were removed, and 73 vouchers from the Carrizo Badlands were eliminated, leaving 105 vouchers of 52 taxa. The dominant collectors in the Consortium records were Joe Barth, 26 vouchers; Jon P. Rebman, J. Gibson, A. Winner, & misc. botany vols., 47 vouchers (of 15 unique collection numbers); and Duffie Clemons, Erik Jonson, Mike Curto, 13 vouchers.
The San Diego records were retrieved for grid cells F26-F29 and G26-G29. One record of Clematis lasiantha was rejected, after an examination of the locality field revealed that the coordinates for this record were erroneous. This resulted in 150 vouchers of 80 taxa. Note that some of the San Diego vouchers also appear in the Consortium records. Only the Plant Atlas records are identified with collector. The dominant collector by far in the San Diego records was jb2 with 51 vouchers; the next largest collector had 7 vouchers.
The determinations for all San Diego Plant Atlas vouchers were all marked as verified by Jon Rebman except for the single voucher of Pectis papposa var. papposa which most likely had simply not yet been processed yet. There are many vouchers of this taxon nearby.
The size of the area delineated in red in the map above is roughly 51 square miles. However, the San Diego Plant Atlas voucher search covered eight Plant Atlas Grid Cells, a total of 72 square miles. On 21 November 2014, I examined the localities in the Consortium of all the species from this voucher set that we have not observed in this area, and tossed species without vouchers actually in the target area.
On 16 December 2007, there were 95 total unique taxa found by combining the two searches. Two of these taxa, Isocoma acradenia var. acradenia and Helianthus niveus ssp. tephrodes, did not appear in Floristic Area #16 in Duffie Clemons' 1985 Checklist of Vascular Plants of the Anza-Borrego Desert, but are present in the 2006 San Diego County Checklist.
Since 16 December 2007, I have augmented the vouchers as I have come across additional records in the course of other work. In particular, in late November 2008 I added a few records from searches for species that I had observed in the Santa Rosa Mountains but which had no vouchers recorded in my database.
The total number of vouchered taxa was 98 on 7 December 2008 from the first voucher search. Only 60 taxa were vouchered from the georeferenced vouchers retrieved on 30 November 2013. After tossing those species without vouchers actually in the target area, on 21 November 2014 the total number of taxa with vouchers is 97.
Fig. 2 shows the locations where we have recorded GPS points for individual species in this area.
Fig. 2. Locations where we have recorded GPS points for individual species in the Borrego Badlands area as of 15 December 2014. GPS Points from later surveys are not yet included in these maps. Left: map of individual GPS points. Note that some locations have as many as 40 species recorded at the same point. Right: cluster version showing how many points are in each area.
Click on the maps for larger versions.
Field surveys were done of the following areas:
- Ella Wash to Vista del Malpais along Ella and Short Wash, returning via Palo Verde and Smoke Tree Wash, on 4 December 2008 (by Tom Chester, finding 46 species) and on 11 March 2009 (by Tom Chester, Mike Crouse and Dave Stith, finding 81 species). A total of 6.0 unique miles were surveyed, with a total of 87 species from the union of the two surveys.
- the Arroyo Salado / Seventeen Palms / Five Palms Spring area on 19 December 2008 (by Tom Chester and Mike Crouse) and 23 March 2009 (by Tom Chester and Mike Crouse). A total of 4.4 unique miles were surveyed, with a total of 78 species from the union of the two surveys..
- The portions of Inspiration Wash and Fonts Point Wash near Highway S22 on 28 December 2005 (by Tom Chester) and 11 December 2007 (by Tom Chester). A total of 1.5 unique miles were surveyed
- A loop containing Fonts Point on 15 December 2007 (by Tom Chester, Wayne Armstrong). A total of 2.0 unique miles were surveyed, finding just 23 species.
- A loop from the Borrego Dump site, through the Borrego Dunes into the Borrego Badlands Area on 20 February 2009 (by Tom Chester, Michael Charters and Dave Stith). This survey was partially in the Borrego Valley area, and partially in the Borrego Badlands area. It has not yet been processed for the flora on this page.
- A survey in the Beckman Wash area on 10 January 2010 by Tom Chester, Anne Kelly, RT Hawke, Aaron Schusteff, Bill Sullivan and Pam Pallette. A total of 0.7 unique miles were surveyed, finding 29 species.
- Fonts Point on 15 November 2014 (by Keir Morse), adding six species to the Fonts Point flora.
- A 5.5 mile loop from the beginning of the Thimble Trail at S22, to roughly south 0.7 miles, then west 2.3 miles toward the hill called Paint on the topo map near Fonts Point Wash, then return on the north side of those Badlands Hills. This survey was done by Tom Chester, Keir Morse, Adrienne Ballwey, and Whitney Meier on 10 December 2014, finding 41 species.
- Two separate short surveys done on 15 December 2014 by Tom Chester, Keir Morse and Adrienne Ballwey in the area of the southern Thimble Trail. One survey was of 1.8 miles in a tributary to Short Wash just north of the southern end of the Thimble Trail, finding just 20 species. Another survey was of just 0.2 mile southwest of the south end of the Thimble Trail, finding just 14 species.
- A survey of Inspiration Wash to Inspiration Point on 9 January 2016 by Tom Chester, Keir Morse, Fred Melgert, Carla Hoegen, and Don Rideout. One new species was added to the Borrego Badlands Flora, a single plant of Orobanche cooperi.
- A survey of two of the upper tributaries of Fonts Point Wash to the Rim on 13 January 2016 by Tom Chester, Mike Crouse, Kate Harper, and Keir Morse.
Field Work near Fonts Point Wash
I recorded all species seen in the parts of Inspiration Wash and Fonts Point Wash near Highway S22 during targeted searches for Pilostyles thurberi and Psorothamnus emoryi on 28 December 2005, augmented by one species seen on 11 December 2007. A total of just 23 species were found in those searches.
Wayne Armstrong and I recorded all species seen on 15 December 2007 in a 2 mile loop containing Fonts Point; just 24 species were found in that search.
A total of 35 taxa were found in those December searches; 11 of those 35 taxa, 31%, are not among the 16 December 2007 vouchered species.
On 15 November 2014, Keir Morse added five species to the Fonts Point flora, and one species to the Inspiration Wash and Fonts Point Wash near Highway S22 flora.
Field Work from Ella Wash, Short Wash, Vista del Malpais, Palo Verde Wash and Smoke Tree Wash
On 4 December 2008, I recorded all species seen on an 8 mile loop trip from S22 at Ella Wash to Vista del Malpais along Ella and Short Wash, returning via Palo Verde and Smoke Tree Wash. A total of 44 taxa were found that could be fairly confidently identified, and are given in the checklist below. Three other species were seen: an unknown dead annual like Chaenactis; a dead Cryptantha species probably distinct from the C. barbigera in the checklist; and a dead annual grass that may have been Schismus barbatus.
Dave Stith, Mike Crouse and I did this loop again at prime time on 11 March 2009.
Field Work from Arroyo Salado / Seventeen Palms / Five Palms Spring area
Mike Crouse and I surveyed this area on 19 December 2008 and again at prime time on 23 March 2009.
Field Work from Beckman Wash area
On 10 January 2010, Tom Chester, Anne Kelly, RT Hawke, Aaron Schusteff, and Pam Pallette surveyed a 0.7 mile loop, finding just 29 species. Annual germination was almost non-existent on this survey, except for Brassica tournefortii.
Summary of Checklist and Species Not Found
As of 20 November 2014, the total number of taxa presented below is 133, 125 of which are native (the list may have been updated after this summary was done). The list contains 134 entries, since the species Cryptantha barbigera is given as well as its two varieties found here, since the earlier surveys did not distinguish the two varieties.
It is likely that this area may have the lowest native biodiversity of any part of San Diego County for the following reasons:
- there is little total elevation relief;
- the landscape is similar throughout the Badlands;
- much of the landscape is eroding rapidly, with very steep slopes, preventing plants from getting established; and
- much of the soil is highly alkaline, which is not tolerated by most species.
An area of this size, roughly 51 square miles, in most of the rest of San Diego County would have roughly 500 native species, whereas this area has just 135 so far recorded. Oddly, the next most depauperate area in my database is San Clemente Island, with 233 native taxa in 57 square miles.
Although the number of species may be small, any area that contains Southern California's Most Unusual Wildflower, along with rarely-seen southern California species such as Orcutt's woody-aster, Xylorhiza orcuttii and Algodones Dunes sunflower, Helianthus niveus ssp. tephrodes, is still of major botanic interest.
It is interesting that the list contains no lycophytes (Selaginella), no ferns, and no gymnosperms. Table 1 gives the most common Borrego Desert species that are not known from the Borrego Badlands.
Table 1. The Most Common Borrego Desert Species That Are ***Not*** Known From The Borrego Badlands
# areas Common Name Scientific Name 54 Gander's cholla Cylindropuntia ganderi 43 teddy-bear cholla Cylindropuntia bigelovii 42 California trixis Trixis californica var. californica 42 common phacelia Phacelia distans 41 San Felipe dogweed Adenophyllum porophylloides 39 woolly lipfern Cheilanthes parryi 38 rock hibiscus Hibiscus denudatus 38 jojoba Simmondsia chinensis 37 Parish's viguiera Bahiopsis parishii 37 California buckwheat Eriogonum fasciculatum var. polifolium 35 Engelmann's hedgehog cactus Echinocereus engelmannii 34 thick-leaved ground cherry Physalis crassifolia 34 California fish-hook cactus Mammillaria dioica 31 chuparosa Justicia californica 31 arrow-leaf Pleurocoronis pluriseta 31 desert woolly-star Eriastrum eremicum ssp. eremicum 30 whispering bells Emmenanthe penduliflora var. penduliflora 30 star-flowered bedstraw Galium stellatum 30 California fagonia Fagonia laevis 29 Mojave ragwort Senecio mohavensis 29 western tansy-mustard Descurainia pinnata 29 bajada lupine Lupinus concinnus 29 Wright's buckwheat Eriogonum wrightii var. nodosum 28 Mormon tea Ephedra aspera 27 Vasey's sage Salvia vaseyi 27 apricot mallow Sphaeralcea ambigua var. ambigua 27 threadstem Pterostegia drymarioides 27 Anderson's boxthorn Lycium andersonii 26 California matchweed Gutierrezia californica 25 desert lotus Acmispon rigidus 25 purple three-awn Aristida purpurea 25 desert spike-moss Selaginella eremophila 24 curvenut combseed Pectocarya recurvata 24 California juniper Juniperus californica 23 Fremont pincushion Chaenactis fremontii 23 linear-leaved stillingia Stillingia linearifolia 23 desert apricot Prunus fremontii 22 star gilia Gilia stellata 22 London rocket Sisymbrium irio 22 California filago Logfia filaginoides 22 short-winged deerweed Acmispon glaber var. brevialatus 22 intermediate larkspur Delphinium parishii ssp. subglobosum 22 ayenia Ayenia compacta 21 Texas filaree Erodium texanum 21 boundary goldenbush Ericameria brachylepis 21 desert dudleya Dudleya saxosa ssp. aloides 20 desert brickellia Brickellia desertorum 20 beetle spurge Euphorbia eriantha 20 short-bannered coastal lotus Acmispon maritimus var. brevivexillus 20 white fiesta flower Pholistoma membranaceum
Checklist for Borrego Badlands
- Notes on the Scientific Names Used At This Site and
- Information about the order in which the species are presented, and the links from the Scientific Name and Common Name.
An asterisk before the common name indicates a non-native species.
The column #V gives the number of vouchers for this area, with a maximum value of 9.
The columns with the header #Pls gives the minimum number of plants for each species observed in each area, up to a maximum of 99, except for the species observed by Keir Morse, which have the entry KM.
The column headers for the individual areas are:
- IW: Inspiration Wash to Inspiration Point, including the other upper tributaries of Inspiration Wash
- FP: Fonts Point Wash to Fonts Point, including the other upper tributaries of Fonts Point Wash
- TT: The Thimble Trail north loop
- EW: The Ella Wash loop
- AS: The Arroyo Salado loop
These areas are in order from west to east.
No column is given for the Beckman Wash survey, or the surveys at the south end of the Thimble Trail.
Note that monsoonal species are not well-represented in the checklist for all areas due to a lack of summer / fall surveys in good monsoonal years, and winter annual / perennial species are not well-represented for some areas due to the lack of surveys in those areas in good winter rainfall years.
On the 12/4/08 Ella Wash survey, a dead skeleton of what appeared to be a Nemacladus species was found. That doesn't appear in the checklist since the determination could not be made to species.
Version for printing, without lines and other text on this page: html (5 pages) or pdf Clickbook booklet (1 double-sided page). (See printing instructions for an explanation of these options)
# Famil Scientific Name (*)Common Name #V # Plants IW FP TT EW AS Eudicots 1 Amara Tidestromia suffruticosa var. oblongifolia Arizona honeysweet 1 5 5 1 2 Apocy Asclepias albicans white-stemmed milkweed 1 1 3 Apocy Asclepias subulata rush milkweed 4 7 7 1 1 4 Apocy Funastrum hirtellum rambling milkweed 1 5 Apoda Pilostyles thurberi Thurber's pilostyles 2 11 35 6 Aster Ambrosia dumosa burroweed 4 99 99 99 99 99 7 Aster Ambrosia salsola var. salsola cheesebush 3 1 99 99 8 Aster Baileya pauciradiata Colorado Desert marigold 4 9 Aster Bebbia juncea var. aspera sweetbush 99 5 10 Aster Calycoseris wrightii white tackstem 1 1 30 11 Aster Chaenactis artemisiifolia meally white pincushion 1 12 Aster Chaenactis carphoclinia var. carphoclinia pebble pincushion 2 99 13 Aster Chaenactis carphoclinia var. peirsonii Peirson's pincushion 2 14 Aster Chaenactis stevioides desert pincushion 1 99 30 15 Aster Dicoria canescens desert dicoria 5 10 99 16 Aster Encelia farinosa brittlebush 4 2 10 99 17 Aster Encelia frutescens button encelia 3 18 35 40 2 18 Aster Geraea canescens hairy desert-sunflower 3 15 50 99 99 19 Aster Helianthus niveus ssp. tephrodes Algodones Dunes sunflower 2 20 Aster Helianthus petiolaris ssp. canescens gray desert sunflower 5 2 21 Aster Isocoma acradenia alkali goldenbush 1 50 99 99 50 22 Aster Malacothrix glabrata desert dandelion 1 50 20 23 Aster Monoptilon bellioides desert star 2 99 40 24 Aster Palafoxia arida var. arida Spanish needle 4 20 30 99 50 30 25 Aster Pectis papposa var. papposa chinch-weed 1 99 15 99 26 Aster Perityle emoryi Emory's rock-daisy 1 20 50 27 Aster Psathyrotes ramosissima turtleback 5 28 Aster Rafinesquia neomexicana desert chicory 1 99 50 29 Aster Stephanomeria pauciflora wire-lettuce 1 15 50 10 99 20 30 Aster Trichoptilium incisum yellow-head 1 31 Aster Xylorhiza orcuttii Orcutt's woody-aster 2 70 6 2 50 32 Bigno Chilopsis linearis ssp. arcuata desert-willow 1 99 33 Borag Cryptantha angustifolia narrow-leaved cryptantha 4 20 30 1 99 99 34 Borag Cryptantha barbigera bearded cryptantha 1 50 1 35 Borag Cryptantha barbigera var. barbigera bearded cryptantha 36 Borag Cryptantha barbigera var. fergusoniae Santa Rosa Mountain bearded cryptantha 37 Borag Cryptantha costata ribbed cryptantha 1 38 Borag Cryptantha ganderi Gander's cryptantha 2 39 Borag Cryptantha maritima Guadalupe cryptantha 1 10 99 50 99 40 Borag Eucrypta micrantha desert eucrypta 1 41 Borag Pectocarya heterocarpa chuckwalla pectocarya 2 50 42 Borag Pectocarya platycarpa broad-fruited combseed 1 43 Borag Phacelia crenulata var. ambigua heliotrope phacelia 1 99 99 44 Borag Phacelia crenulata var. minutiflora little-flowered heliotrope phacelia 1 1 3 45 Borag Tiquilia palmeri Palmer's coldenia 3 30 50 99 99 4 46 Borag Tiquilia plicata plicate coldenia 50 99 50 47 Brass Brassica tournefortii *Asian mustard 2 50 80 99 99 99 48 Brass Dithyrea californica spectacle-pod 2 30 49 Brass Lepidium lasiocarpum ssp. lasiocarpum hairy-podded pepper-grass 2 5 10 99 99 50 Brass Streptanthella longirostris longbeak streptanthella 99 51 Cacta Cylindropuntia echinocarpa silver cholla 1 50 45 75 20 6 52 Cacta Cylindropuntia ramosissima pencil cholla 15 4 30 53 Cacta Ferocactus cylindraceus California barrel cactus 2 54 Cacta Opuntia basilaris var. basilaris beavertail cactus 15 2 2 55 Caryo Achyronychia cooperi frost mat 1 1 10 56 Cheno Atriplex canescens var. laciniata Caleb saltbush 1 15 50 99 40 57 Cheno Atriplex hymenelytra desert holly 4 50 99 4 99 99 58 Cheno Atriplex polycarpa cattle saltbush 20 99 2 20 30 59 Cheno Chenopodium murale *nettle-leaved goosefoot 2 60 Cheno Salsola tragus *Russian thistle 2 15 1 61 Cheno Suaeda nigra bush seepweed 30 62 Cleom Cleomella obtusifolia Mojave cleomella 2 99 63 Eupho Chamaesyce abramsiana Abrams' prostrate spurge 99 64 Eupho Chamaesyce micromera Sonoran spurge 99 99 65 Eupho Chamaesyce polycarpa small-seeded spurge 3 35 99 99 5 66 Eupho Croton californicus California croton 8 50 40 99 67 Eupho Ditaxis lanceolata narrowleaf ditaxis 1 1 68 Eupho Stillingia spinulosa annual stillingia 3 69 Fabac Acmispon strigosus strigose lotus 1 50 4 70 Fabac Astragalus crotalariae Salton milk-vetch 4 99 5 1 71 Fabac Astragalus didymocarpus var. dispermus dwarf white milk-vetch 1 72 Fabac Astragalus lentiginosus var. borreganus Borrego milk-vetch 6 73 Fabac Dalea mollis silky dalea 3 99 74 Fabac Dalea mollissima downy dalea 2 sp1 75 Fabac Lupinus arizonicus Arizona lupine 2 99 99 76 Fabac Parkinsonia florida blue palo verde 2 30 77 Fabac Prosopis glandulosa var. torreyana honey mesquite 1 1 1 40 78 Fabac Psorothamnus emoryi Emory's indigo-bush 2 30 95 60 10 79 Fabac Psorothamnus schottii indigo bush 75 99 5 99 50 80 Fabac Psorothamnus spinosus smoke tree 30 99 30 81 Fabac Senegalia greggii catclaw 20 50 82 Fouqu Fouquieria splendens ssp. splendens ocotillo 2 99 99 99 50 30 83 Geran Erodium cicutarium *redstem filaree 1 1 84 Krame Krameria bicolor white rhatany 50 99 99 50 50 85 Krame Krameria erecta Pima rhatany 2 99 86 Lamia Hyptis emoryi desert-lavender 1 50 20 87 Lamia Salvia columbariae chia 1 88 Loasa Mentzelia albicaulis white-stemmed blazing star 10 10 89 Loasa Mentzelia involucrata bracted blazing star 1 1 20 90 Loasa Petalonyx thurberi ssp. thurberi Thurber's sandpaper-plant 2 50 30 5 91 Malva Eremalche rotundifolia desert five-spot 1 5 92 Mollu Mollugo cerviana *carpet-weed 10 93 Monti Cistanthe ambigua desert red maids 1 99 99 94 Nycta Abronia villosa var. villosa hairy sand-verbena 9 1 1 4 99 40 95 Nycta Allionia incarnata var. incarnata trailing four o'clock 1 2 99 96 Nycta Boerhavia wrightii Wright's spiderling 1 2 97 Nycta Mirabilis laevis var. retrorsa Bigelow's desert four-o'clock 2 98 Nycta Mirabilis laevis var. villosa Bigelow's desert four-o'clock 2 99 Onagr Chylismia cardiophylla ssp. cardiophylla heartleaf suncup 1 100 Onagr Chylismia claviformis ssp. peirsonii brown-eyed primrose 2 99 99 99 99 101 Onagr Eremothera boothii ssp. condensata Booth's evening primrose 2 40 40 10 99 40 102 Onagr Eulobus californicus California suncup 2 5 50 1 103 Onagr Oenothera deltoides ssp. deltoides dune primrose 1 20 2 30 1 104 Oroba Orobanche cooperi Cooper's broomrape 1 105 Papav Eschscholzia minutiflora ssp. minutiflora small-flowered poppy 99 99 106 Papav Eschscholzia parishii Parish's poppy 1 41 1 107 Plant Plantago ovata desert plantain 3 50 50 1 99 108 Polem Aliciella latifolia ssp. latifolia broad-leaf gilia 1 40 10 109 Polem Langloisia setosissima ssp. setosissima bristly langloisia 1 40 110 Polem Loeseliastrum schottii Schott's calico 20 25 20 20 111 Polyg Chorizanthe brevicornu var. brevicornu brittle spineflower 2 5 10 99 50 112 Polyg Chorizanthe corrugata wrinkled spineflower 1 99 40 113 Polyg Chorizanthe rigida devil's spineflower 1 5 99 99 20 114 Polyg Eriogonum deflexum var. deflexum flat-topped buckwheat 3 20 2 20 115 Polyg Eriogonum inflatum desert trumpet 1 1 99 10 116 Polyg Eriogonum thomasii Thomas' buckwheat 1 99 99 117 Polyg Eriogonum trichopes little desert trumpet 2 99 99 99 20 118 Resed Oligomeris linifolia lineleaf whitepuff 3 3 99 99 119 Solan Lycium brevipes var. brevipes desert boxthorn 20 120 Solan Nicotiana obtusifolia desert tobacco 2 121 Tamar Tamarix sp. *tamarisk 1 122 Visca Phoradendron californicum desert mistletoe 10 40 123 Zygop Kallstroemia californica California caltrop 99 99 124 Zygop Larrea tridentata creosote bush 2 99 99 99 99 99 Monocots 125 Agava Agave deserti var. deserti desert agave 1 126 Agava Hesperocallis undulata desert lily 4 3 3 99 40 127 Areca Washingtonia filifera California fan palm 23 128 Junca Juncus cooperi Cooper's rush 5 129 Poace Aristida adscensionis six-weeks three-awn 20 60 99 10 130 Poace Aristida californica California three-awn 3 131 Poace Bouteloua barbata var. barbata six-weeks grama 30 10 132 Poace Bromus madritensis ssp. rubens *red brome 2 133 Poace Dasyochloa pulchella fluff grass 50 134 Poace Distichlis spicata saltgrass 99 135 Poace Hilaria rigida big galleta 2 99 99 99 40 99 136 Poace Hordeum murinum *foxtail barley 99 137 Poace Phragmites australis common reed 10 138 Poace Schismus barbatus *Mediterranean schismus 2 99 99 99 99 139 Poace Stipa hymenoides Indian ricegrass 4
Copyright © 2007-2016 by Tom Chester (see list of people who participated in each of the surveys)
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Last update: 16 January 2016