Conservation policy and practice usually value native species of plant over introductions: they are our particular responsibility just as Eucalypts are the Australians’ and Sequoias the Americans’. Native usually means those plants that arrived under their own steam after the last glaciation and formed part of our natural vegetation. However, while the nativeness concept seems simple there are more twists and turns that at first appear.
For example, some proponents of rewilding use previous interglacials as a model of what natural landscapes might look like to sidestep the consequences of the extinction of mega-fauna by Paleolithic peoples. If that approach were taken with plant nativeness it would bring in some interesting plant species, since at various times rhododendron and Norway spruce have been present in what is now Britain.
Norway spruce and rhododendron have been ‘native’ to Britain in the distant past.
There are then the species thought to be early, probably accidental, introductions which are classed as archaeophytes (present before 1500) in the Atlas of the Flora of Britain and Ireland (Preston et al., 2002). Some of these are arable weeds, such as corn cleavers, that are the subject of active conservation programmes. Others such as white dead-nettle are just accepted. Sycamore, classed as neophyte (recorded only post-1500 in the wild), but arguably an archaeophyte, have been the subject of major conservation control programmes.
Ploughing part of an SSSI to benefit corn cleavers; white dead-nettle, another archaeophyte.
Attitudes to sycamore are changing because of its potential in the face of loss of ash and because of claims that it may even be native. Reclassification has affected other species. Snowdrop has at times been argued as native to Britain but is classed as an introduction. May Lily has been classed as an introduction in the past but is now accepted as native at some sites.
Snowdrops and May lily.
Species that have obviously been introduced beyond their range, as with beech in northern England and Scotland are treated as not native to those areas, even though they may now be fully naturalised. On a smaller scale, I found soft shield fern in Wytham Woods this summer – a first record for the site. It is not that common in the surrounding 10 km squares and the spores probably blew in from a nearby garden. So, it may not be from a natural population, but as far as I am concerned it is now part of the native list for the Woods.
Naturalised beech in north-east Scotland; soft shield-fern, a recent invader of Wytham Woods.
Species ranges also change over time: might beech have reached Scotland by now without human help and how could we tell? Its distribution on the continent has been changing over the last few thousand years (Bradshaw and Lindbladh, 2005). Other changes in species distributions are happening because of climate change, most obviously with some invertebrates and birds. There are rather few reported range shifts for woodland plants as yet, probably because of their low dispersal ability and the fragmented nature of ancient woodland in Britain. If we accept that humans are the major cause of both the climate change and the woodland fragmentation, there is then a case for arguing that we should also intervene in helping species cope with these problems by translocating plants. We might also accept the odd near-continental species that escapes from gardens into woods.
Liverleaf, an attractive species from the near-continent that occasionally escapes from gardens into woods.
Molecular analysis is throwing up other intriguing questions on origins (Preston et al., 2012). The Welsh poppy is a native species in Wales, but many of the populations elsewhere, thought to be derived from garden escapes, seem to have genetic links to a different glacial refuge in the central and eastern Pyrenees. The native genotype seems to be in slow decline, but the otherwise almost indistinguishable version is expanding its range. Is that good or bad news for poppy conservation?
Welsh poppy, a native species but non-native genes in this case
As a teenager I was into English folk music and we put great store on songs deemed to come from the ‘oral tradition’, the real folk songs. Yet that did not stop us also joining in with recent ones written by Ewan McColl or Tom Paxton where they were good ballads. In the same way perhaps we should become more accepting of non-native species in the face of rapidly changing environments. Last summer I revisited Urquhart Bay Alderwood on the shores of Loch Ness. The Woodland Trust noticeboard referred to control of Himalayan balsam and Japanese knotweed as invasive species, but seemed accepting of the abundant sweet cicely, goutweed, pink purslane, honesty, lupins, fringe-cups and Welsh poppy.
Urquhart Bay with its interesting flora including stands of goutweed and fringecups.
BRADSHAW, R. H. W. & LINDBLADH, M. 2005. Regional spread and stand-scale establishment of Fagus sylvatica and Picea abies in Scandinavia. Ecology, 86, 1679-1686.
PRESTON, C. D., PEARMAN, D. A. & DINES, T. D. 2002. New Atlas of the British and Irish Flora: An Atlas of the Vascular Plants of Britain, Ireland, The Isle of Man and the Channel Islands Oxford, Oxford University Press.
PRESTON, C. D., VALTUEÑA, F. J. & KADEREIT, J. W. 2012. The intriguing case of the Welsh poppy Meconopsis cambrica. British Wildlife, 24, 16-20.