Wednesday, 18 August 2010

Signs of the times: Summer #12

More comparisons between the British countryside of today and that from 1959-1961 in the paintings of Charles Tunnicliffe in the Ladybird "What to look for..." series of books.

"Oh, the summer night
Has a smile of light
And she sits on a sapphire throne."

Barry Cornwall

(Copyright: Ladybird Books)

Summer Picture 12
I think this is the first night-time picture of this series of posts. It shows a roadside scene with a hedgehog that “has “frozen” in sudden alarm” in the verge, as car headlights illuminate a floral scene of Plantain with its brown seed heads already formed, the ground-level yellow-flowering Common Bird’s-foot Trefoil, the tall, pink-flowered Betony, grasses and White Clover, all underlain by a carpet of ground ivy. A pair of slugs are perilously close to the hedgehog. Male and female Drinker moths are also lit up in the headlights, while the “cuckoospit” foam “homes” of froghopper larvae adorn the stems of the Betony. The following discussion of the fate of the picture’s represented features is quite lengthy as there are several interesting stories raised by this collection of species (well, they interest me at any rate), so apologies for the length – I hope you think it is worth it if you make it to the end!

The hedgehog (Latin name: Erinaceus europaeus) may be the native British mammal most popular with the citizenry of the country while, at the same time being perhaps the one most often killed accidentally by the same citizenry in their cars. The hedgehog belongs to the insectivore (“insect-eating”) mammal order (Insectivora) along with, in Britain, the mole and the shrews. This implies that hedgehogs are insect feeders when, although they will take larger ground-living insects, they will also feed on other invertebrates, such as slugs and snails, and will take eggs and chicks from the nest of ground-nesting birds. The Joint Nature Conservation Committee (JNCC) Review of British Mammals summarises the habitat preferences of the hedgehog as follows:  “Found throughout mainland Britain up to the treeline, but scarce or absent from very wet habitats, areas of large arable fields and conifer plantations. Although there are occasional records of animals foraging at higher altitudes…, they are probably absent from many upland areas, especially in Scotland. They are also found on many islands, often as a result of introductions... Recent (1970s and 1980s) introductions include North Ronaldsay (Orkney) and St Mary's (Isles of Scilly)… Hedgehogs are most abundant where there is close proximity of grassland to woodland, scrub or hedgerow, and they are present in virtually all lowland habitats where there is sufficient cover for nesting. They are common in suburban areas, but generally scarce in coniferous woods and marshy and moorland areas.”

As hedgehogs are largely nocturnal foragers, we probably underestimate how many are living around us. I recall some research a couple of years ago that concluded that if you are regularly seeing a hedgehog in your garden, their population density and ranging behavior mean that there may be up to 26 hedgehogs actually visiting your garden. So what has happened to hedgehog populations in recent decades? The most recent estimate, in the JNCC review is, very approximately for a total pre-breeding population of about 1,555,000; 1,100,000 in England, 310,000 in Scotland and 145,000 in Wales. At the beginning of the 20th century, hedgehogs were described as plentiful throughout the greater part of Great Britain, in spite of constant persecution by farmers and gamekeepers, though scarce in the northern highlands of Scotland. The JNCC review records that, with hedgehogs being introduced to western Ross-shire in 1890 in baled hay and to the eastern parts of Sutherland and Caithness, it would appear that hedgehogs were extending their range in Scotland in the second half of the 19th century.

But it is very difficult to know exactly what is happening to population trends for a cryptic night-time mammal like the hedgehog. The JNCC report pulls together evidence from a range of published and unpublished studies that suggest that the British hedgehog population is probably shrinking. Data from a survey called the National Game Bag Census suggest a steady reduction in the numbers killed, possibly dating from before the 1960s. Whether this is the result of a population decline due to an increasing loss of suitable habitats, or a change in gamekeeping practice, is not easy to determine. There are separate estimates of around 100,000 hedgehogs killed a year on the British road network (the hedgehog in this picture is identified, in the book’s accompanying text, as having frozen in alarm as the car headlights appear – smart hedgehog!).

It is likely, however, that changes in agricultural landscapes over the past few decades would have had a greater effect on hedgehog numbers than either gamekeepers or road traffic, particularly the change from permanent grassland and rough grazing to arable farmland, a less suitable habitat for hedgehogs due to it supporting a lower earthworm population. In addition, the removal of hedgerows and resulting increase in field sizes limits the availability of nesting sites, further reducing the suitability of arable land for hedgehogs; the JNCC concludes that a shortage of suitable nesting sites generally may be a factor limiting hedgehog numbers.

There is also a suggestion that pesticide residues from agrochemicals and garden pesticides, especially molluscicides (that’s slug pellets to you and me!), potentially have an impact through the food chain, but no data have been collected on the pesticide levels present in hedgehogs, with still less available on their effects on the hedgehog population overall. The final pressure on hedgehogs identified is that of climate change – hedgehogs must reach a minimum weight of 450g in order to survive a normal period of hibernation. Hot dry summers reduce the availability of earthworms and other invertebrate prey of hedgehogs, and this may have a significant impact on hedgehog numbers and/or the survival of young. The Mammal Society provides an interesting information sheet on the hedgehog here. If you want to make your garden more hedgehog-friendly (and who wouldn't?), you could do worse than look at this website here.

The Drinker moths (Philudoria potatoria) in the picture are a widespread and abundant moth species throughout Britain, found in all sorts of open habitats. Natural England says of this species: “This large moth is common and widespread in Great Britain, and can be found in gardens where there are stands of coarse and lightly managed grasses.”

Of the plants in the picture, the plantain in the bottom right is probably the most widespread in Britain. It looks to me like the Ribwort plantain (Plantago lanceolata), a perennial plant found extremely widely on all but the most acidic of soils. The New Atlas of the British and Irish Flora reports that its habitats range across: “meadows and pastures, in upland grasslands, on rock ledges and crevices, sand dunes and cliffs (including sites subject to sea-spray), on roadsides and river banks, in cultivated and waste ground, in lawns and on walls.” The New Atlas reports that there has been no change in its distribution since the 1962 Atlas. Richard Mabey's Flora Britannica has a fascinating account of the games traditionally played by children with this aprticular species, for eample a substituted form of conkers using plantain stalks and heads instead of horse-chestnuts on strings - my own childhood experience was of using plantain seed heads to make little pop guns, folding the stalk over on itself and pulling the resultant “catch” against the seed head to fire it at the target, usually your friends!

The flower heads of the White Clover (Trifolium repens) are quite distinctive, just above the hedgehog’s head. The New Atlas identifies that this species, recorded it seems in almost every 10 km square in Britain, occurs “in grasslands on all but the wettest or most acidic soils; also on waste ground and in other ruderal habitats. It is very tolerant of grazing, mowing and trampling and is often scarce or absent in taller grassland. It is very widely sown as a component of short and medium term leys, and on roadsides, and many commercial cultivars are available.” It also reports that there has been no change in the distribution of this ubiquitous species since the 1962 Atlas.

I admit that the tall, leggy pink flowering plant, the Betony (Stachys officianalis), shown here above the hedgehog, is not a species I had even heard of before I embarked on this Ladybird book project. And checking its distribution in the New Atlas, its range barely reaches Scotland. According to the New Atlas, Betony has: “suffered local losses in England and Ireland as a result of the loss and improvement of permanent pastures, the ploughing of fields to the edge of woods with consequent loss of the marginal flora and the shading of woodland grassland following a decline in coppicing.”

This last cause of problems for this species, caused by the withering of a traditional form of management of copses and woodland, illustrates well the extent to which much of our “countryside” and all of its associated riches of wildlife (“biodiversity” simply being the current in vogue term for this richness) has been created by (and is dependent for its ongoing survival on) human action and management. Britain is not particularly rich in species per se, when compared to some of the “biodiversity hotspots” on the planet, but what it does have is a remarkable diversity of habitats for such a small island archipelago, from the remaining pockets of truly wild and relatively undisturbed habitats, such as large areas of our marine habitats (particularly in Scotland), the high montane habitats of the Cairngorms and small areas of Caledonian pinewoods, to traditionally farmed landscapes such as the machair grasslands of the Outer Hebrides and northwest Scotland, and the range of different agricultural, woodland, urban fringe and urban environments created and maintained by human activity.

This diversity of habitats has created a wide range of niches for different species, likely to be far greater than that in pre-settlement Britain, when wild forest, dominated largely by oak or pine, stretched from coast to coast, and open habitats, other than high montane, coastal dunes, and wetlands were much more restricted. What we see as countryside today, or at least perhaps up until the period of real agricultural intensification since the Second World War, is the product of hundreds, perhaps thousands of years of forest clearance and extensive (i.e. lower intensity) land management and agriculture. What has lost out over this long, long timescale has been forests and, particularly in the last century, wetlands, but Britain would not have the wide array of grasslands, lowland heathlands and other open habitats, and all their associated species, without this history of land-use.

Of course, things went very pear-shaped in the 20th century in a well-documented tale of agricultural intensification and urban development, the effects of some of which on Britain’s wildlife have been touched on so far in this series. Humans, eh? Can’t live with ‘em, can’t live without ‘em...

Returning to the detail of the picture, the small yellow flowering Birds-Foot Trefoil (Lotus corniculatus), shown bottom left and centre right, is also a very widespread species of British grasslands and is absent from only the most acidic and least fertile of grassland soils. “Bird’s foot” comes from the long, narrow seed-pods which look like one; trefoil means “three-leaved”, although, for accuracy’s sake, it is actually five-leaved with two folded back, giving the impression of three.

This species could be the first wild flower that I remember learning as my dad taught me that, as well as being called Bird’s-foot Trefoil, it is given the common name “Bacon-and Eggs”, as the flowers, although shown as yellow here, often also have big splashes of a deep red/pink that looks like cooked bacon! I remember being told this when I was five or six, at Yellowcraig, a sand-dune system on the East Lothian coast for which my dad was the Ranger. Funnily enough, my wife Olivia learned another common name, “Fingers-and-Thumbs, Bellies-and-Bums” for the same plant. And if you read about this species in Richard Mabey’s “Flora Britannica", he reports that one author collected over 70 traditional names for this obvioulsy popular little flower.

I am most familiar with this lovely little plant from coastal dunes and their associated grasslands, as this is the semi-natural grassland habitat I encountered most frequently while growing up as a young, budding naturalist in East Lothian, where most of the other lowland semi-natural grasslands fell under the plough decades, if not centuries earlier (see “Betony” text above).

Funnily enough, the other habitat where I have seen this commonly (other than while hill-walking, where it is frequently seen) has been on roadside verges where, I suspect, the combination of good drainage and some fertility from nitrogen oxides in exhausts, combined with some salt from road treatments in Winter, simulates the conditions somewhat of coastal grassland. I say “funnily enough”, as I was expecting, as has been the case with some other plants in this series of posts, to find that its distribution in Scotland (and Britain more widely) has been extended along the road network, through natural spread and also from deliberate seeding as part of planting schemes for new road developments. But, on consulting the New Atlas, it seems that the: “overall distribution of this species is unchanged since the 1962 Atlas, despite the fact that it is suppressed in improved pastures and is possibly a poor competitor where grazing ceases.” It adds, however, that “Alien genotypes, introduced from seed mixtures, occur on roadsides”, so perhaps these plants shown here aren’t actually from native stock! Although, as this picture was painted before 1960, who knows whether Britain was importing foreign seed mixes for grassland planting schemes at that time, or whether this ecologically unfortunate practice has emerged since then?

Finally, the white, frothy “spit” at the junctions of the leaves and stems of the Betony have been secreted by the larvae of froghoppers, insects from the order of Bugs (Hemiptera), and are commonly knwn as spittle bugs or spit bugs. You can read more about froghoppers here. I tried to track down information about the trend in these insects in the past 50 years,since the book was published but, working from home using the usual search engine approaches, I could find nothing. I did find a general comment on such problems at the website of Buglife, the Invertebrate Conservation charity: "One of the problems facing invertebrate conservationists is our lack of knowledge on their exact status. Perhaps this is unsurprising given that there are 40,000 species and only a few hundred experts who are studying them. However what we do know presents a very worrying picture. Many species are in decline, and significant numbers of species are definitely or feared to be extinct.

  - Worldwide, an estimated 570,000 species could be extinct by 2100.
  - The British Red Data Book for Insects, published in 1987, includes 1786 species whose continued existence is threatened - and that is just for the best known groups."

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