INTRODUCTION

 A. Spalding

1. The aims of this book

This book builds on the 1st edition which aimed to fill a gap in our knowledge about the wildlife of Cornwall and the Isles of Scilly. It is intended to follow in the tradition of the Victoria County History (Page, 1906), which established an inventory of key wildlife species in Cornwall at the end of the 19th century and which is a still a key reference for naturalists today when studying changes in the distribution of species over the years. In the following chapters we attempt to list those species present in the region which are nationally rare, locally scarce or under threat. So-called “flagship species” are included where they are special elements of our local cultural background, for example Scilly Shrew, Cornish Chough, Cornish Bladderseed, Cornish Clingfish and the Cornish Sandhill Rustic. This book also highlights the importance of certain key species when setting nature conservation priorities for habitats.

 The book is based on the simple idea of rarity. Rarity can be based on geographical distribution, the number of separate or linked populations, the abundance of individuals within those populations, or the frequency of genotypes; geographical distribution is used here. There is no necessary implication of threat; nationally rare species can be abundant where they occur and their conservation may be secured by the creation of targeted nature reserves or management plans. Some of the more widespread species may in fact be under greater threat: species such as the commoner moths which we take for granted are currently suffering large declines, all the more drastic because they have been largely unreported. In fact, rarity is rarely used by itself to denote conservation importance. The 2007 Biodiversity Action Plan process used four scientific criteria for the selection of terrestrial/freshwater species: international threat, international responsibility and moderate decline in the UK, marked decline in the UK and the catch-all criterion of “other important factors”, which includes extreme threat linked in some cases to restricted geographical range. Rarity is a key factor in just two of these categories - international responsibility (where the species is rare or absent outside the UK) and “other important factors.” (BAP species occurring in the region are listed in this volume). Nevertheless, rarity is a useful method of separating species from the vast number of common species and allows us to list the key elements of the wildlife that occur in the region.

 2. Selection criteria for Red Data Book species

 The concept of Red Data Books is a simple one, in use for about 30 years. For this book, standard Red Data Book criteria have been used for many of the terrestrial groups, where RDB is the occurrence in 15 or less 10km squares nationally and NS/NN is the occurrence in between 16 and 100 10km squares nationally. The criteria Nationally Scarce/Notable have been sub-divided for some groups into Notable A (occurring in between 16 and 30 10km squares nationally) and Notable B (occurring in between 31 and 100 10km squares nationally). The category Locally Scarce is used where species occur in less than five 10km squares within the region (out of 64 10km squares within Cornwall and four in the Isles of Scilly). Species selection is simplified where there is a national Red Data Book for a particular taxonomic group or an annotated list with RDB or NS notations. In many cases, section authors have interpreted the RDB categories broadly so that species they consider to be key species within the region can be included; the rationale behind the book is to be inclusive and comprehensive, not rigid and restrictive. Thus the categorisation of the less well-known marine species relies on published data, the authors’ experience and numbers of records for sea areas.

 3. Climate change

 It is now generally accepted that climate change will cause increased temperatures and changes in precipitation patterns and cause sea levels to rise around the world (Cowie, 2007). Sea levels have been predicted to rise by 0.09 to 0.88m by the end of the 21st Century (IPCC, 2002) due to terrestrial ice melt and thermal expansion (Cowie, 2007). In Britain the situation is complicated by the fact that the land is rising in the north and sinking in the south (Hopkins, 2008), and in some places such as western Scotland sea level may actually fall in relation to the land due to isostatic rise (Cowie 2007); in Cornwall and the Isles of Scilly sea levels are likely to rise but less than for south-eastern England. Changes in sea levels in the region, recent in geological time, are still visible along the Cornish coast and in the Isles of Scilly, where the islands separated into their current conformation perhaps within the last 1000 years (Thomas, 1985). It is not impossible that a period of faster sea level rise may yet take place, and an 80m increase would occur in the event of total terrestrial ice melt (Cowie, 2007). It is estimated that temperatures will rise between 1.4 and 5.80C by the end of the 21st century (IPCC, 2002) and exceptional heatwaves can be expected to be around 6.50C warmer than those at the beginning of the century (Cowie, 2007). If the Gulf Stream weakens or shifts southwards as a result of new ocean and atmospheric circulation patterns occurring due to a major freshening of seawater (Cowie, 2007), winters could become harsher or become warmer at a slower pace than the summers. In addition to higher temperatures, there are likely to be increased periods of drought and heavy precipitation events will be more common (IPCC, 2002).

 Possingham (1993) suggests that plants and animals will respond to climate change in one or more of the following ways:

 • tolerating change without adaptation

• adapting genetically

• changing distribution

• becoming locally extinct.

 It can already be seen that climate change is affecting the national and international distribution and abundance of a wide range of species. Many species are changing their distributions, either within their habitat or by moving to other habitats. There have been many cases of species moving latitudinally towards the poles or vertically up hills and mountains as climate warms (IPCC, 2002), perhaps as much as 6.1km per decade towards the poles (Parmesan & Yohe, 2003). Root et al. (2003) found that 80% of the species they investigated showed changes shifting in the direction expected with temperature-related shifts, with species at higher latitudes reacting more strongly than species at lower latitudes to changes in temperature. Franco et al. (2006) found that the southern warm range margins of some butterfly species are as sensitive to climate change as are the northern/cool margins, whilst Hickling et al. (2006) found that some of the less well studied groups show an even stronger response to climate change than butterflies and birds, with major latitudinal shifts revealing substantial changes to species’ ranges. Whilst land use change has probably been the strongest driver of 20th century change in the distribution of species, climate change has also been a significant cause (Parmesan & Yohe, 2003). Within Cornwall, we can already see that some species are moving within habitats to cooler areas, for example from south to north-facing slopes where the mean temperatures are lower.

 Where does this leave wildlife species in Cornwall? Marine species dwell in habitats with high levels of connectivity, so that they can respond to changes in temperature perhaps more easily than terrestrial species – although even here species may be restricted to small areas of inter-tidal habitat isolated from adjacent areas. Terrestrial species with particular habitat requirements and low mobility may become isolated in small patches from which they are unable to move as the habitat becomes unsuitable; species with limited climatic ranges and restricted habitat requirements and occurring in small populations are especially vulnerable to local extinction (IPCC, 2002). It is perhaps still too early to predict the potential losses and gains from climate change; in particular, changing precipitation patterns are hard to predict. In some cases, loss of species may be attributed to the effects of climate change; Parslow (2007) attributes the decline of Shore Dock in the Isles of Scilly to the incremental loss of coastal margins to sea level rise. Certainly, habitat management for species needs to take account of possible changes in niche occupancy, otherwise some of the key species may disappear from our nature reserves. It may also be necessary to take the bold step of moving threatened species to new areas that may be outside their current or historical range, where they will be able to cope with the effects of higher temperatures, changing precipitation patterns and perhaps rising sea levels (see for example Hoegh-Guldberg et al., 2008). Climate change represents one of the major challenges to the conservation of wildlife within the region. It is already considered to be a factor for the conservation of several species mentioned in the following accounts and it is to be hoped that this book will provide a baseline audit against which the effects of climate change can be measured.