Much is written about connecting protected areas with the aim of achieving landscape-scale nature conservation, and the problems of isolation, fragmentation, edge effects and so on in small, disconnected sites are well known, even if some of the mechanisms involved are not fully understood (e.g. Harris 1988, Murcia 1995). There are many examples of areas where species and areas of 'protected' habitat have suffered through a lack of connectivity, both in terms of the landscape itself and the policies and legislation covering them. In Britain, one particular example, the Pashford Pot Beetle Cryptocephalus exiguus, illustrates this issue especially clearly at the national (UK) level.
|C. exiguus, photo © Lech Borowiec|
C. exiguus is a widespread Palaearctic species (in Mongolia and Korea it is known as ssp. amiculus), but in Britain has only been recorded in few scattered sites, mainly in eastern England. Between 1898 and 1954 it was recorded from Freshney Bog, Lincolnshire, but since then it has been known only from a single site - Pashford Poors Fen, Suffolk - with the most recent record from 2000.
|NBN map of C. exiguus distribution|
Pashford Poors Fen is a SSSI (Site of Special Scientific Interest) and a nature reserve managed by the Suffolk Wildlife Trust. Covering 11.3 hectares, it is known for its mosaic of drier grassland and wetter fen areas, both of which support a range of interesting plant and animal species. It is however essentially an ecological island within a sea of intensive land use (mainly agriculture). C. exiguus itself is listed as 'Endangered' (RBD 1) and is covered by the UK Biodiversity Action Plan (BAP). It is a wetland species associated with mixed fen and fen meadow, and although little is known about its biology in Britain, it is believed to feed on Common Sorrel (Rumex acetosa), among other possibile host plants. Targeted survey efforts found small numbers during the 1980s and 90s and concluded that the habitat had degraded to such an extent that it could only support a small population, if any. Although the BAP set a target in 1995 of maintaining the population, and if possible enhancing it with a view to translocating it to other sites, it has not been found since 2000 and BAP reporting in 2005 simply stated 'Target not Achieved'. Given that the species was listed as Endangered in the 1980s and subsequently BAP listed, and the site is a nature reserve designated as a SSSI and managed well by a conservation body, what has happened?
Essentially, this is where the landscape issue comes in. Fojt (1994) noted that fens and their vegetation communities (many of which are localised, some of which are rare, and all of which are of high conservation value) are dependent on calcareous spring water, but that they are threatened by drainage (e.g. for agriculture). Many fens have been damaged by drainage, and although this has been occurring for a long time, spring-dependent communities have often survived. However, more recently there has been increased abstraction of aquifer water, and this fundmentally threatens the ecological functioning of fens both directly and by worsening the effects of droughts (which may well increase in frequency and severity as a result of climate change). Fojt's report notes that changes had already occurred in the species composition of many sites, in some cases changing the type of vegetation community. This of course has knock-on effects on species, such as invertebrates, which rely on particular plant communities. Fojt also notes that groundwater abstraction directly threatens springs and their associated (and nationally important) plant communities although in most cases, the lack of intensive hydrological study makes it difficult to determine the precise impacts of groundwater abstraction on fen water tables. Looking at solutions, Fojt noted that,
"The problem of dehydration due to water abstraction needs to be tackled strategically in the long term, though action needs to be taken over currently existing licences. The alleviation of the problem will be helped if water resource plans accommodate the water demand of those fens with a high wildlife interest."
As with many sites, this true of Pashford Poors Fen which is both small and surrounded by land use which is effectively, through water abstraction and drainage, hostile to its continued well-being, even if unintentionally. In the 1990s, the Suffolk Local BAP stated that action included extension of the SSSI boundary in 1996 to improve control over adjacent drainage ditches, and the installation of additional bunds to attempt to retain higher water levels during the summer. The management plan for the site was rewritten with greater emphasis on the vegetation management of those areas where C. exiguus had been found, focusing on providing an appropriate grazing regime during autumn and early winter. A Water Level Management Plan was mooted to deal with issues relating to control of water resources on the site, but for fens in general these have tended to be inadequate as they do not cover groundwater or water quality.
So, what has happened? Well, no-one knows for certain, but it is likely that C. exiguus is at best extremely rare in Britain, possibly extinct. Of course, it might be rediscovered at Pashford Poors Fen, or indeed at another site. At the Palaearctic scale, it could be argued that this isn't too important - it was rare and localised in Britain even when land management was at least a bit more sustainable (i.e. in the 19th century), and remains widespread elsewhere. However, aside from the intrinsic value of any species as a contributor to national and local biodiversity (and I consider this important in itself), it highlights a major failing in conservation. The site and species were both listed/designated and therefore, in principle at least, protected. The problem had been identified, and required action understood - indeed, as site managers, the Suffolk Wildlife Trust did what they could. Yet, the site has still degraded and the species has probably been lost. Why? Well, it's simply because conservation requirements remain politically a lower priority than many other competing interests. In this case, water abstraction licences for agriculture were granted despite the impact on adjacent wildlife habitat, and regardless of the site's conservation designation and status. This could have been taken into account but wasn't - and so, the fate of the site and species was taken out of the hands of the Wildlife Trust: by the time favourable changes started to be made in policy etc, it was already too late. Still, hopefully the relevant lessons will have been learned...
I could go on about the Government's continued failure to protect Britain's biodiversity (Countdown 2010 anyone...), but - at least for now - I won't. However, this is hardly a unique situation - a recent post by Ted McRae at Beetles in the Bush covers a parallel issue from Missouri - and it seems that, unless conservation requirements become fully integrated and suitably weighted in decision-making and land management/planning processes, it is something that will continue to occur. Still, not all is doom and gloom - since I took over as organiser of the UK Chrysomelid Recording Scheme, two more chrysomelids have been found - Longitarsus symphyti which should be a definite addition to the list, and Smaragdina salicina which is so far known only from a single specimen.
Fojt, W.J. (1994). Dehydration and the threat to East Anglian fens, England. Biological Conservation 69(2): 163-175.
Harris, L.D. (1988). Edge Effects and Conservation of Biotic Diversity. Conservation Biology 2(4): 330-332.
Murcia, C. (1995). Edge effects in fragmented forests: implications for conservation. Trends in Ecology and Evolution 10(2): 58-62.