Extinctions and colonisations Derek Middleton (FLPA)
EXTINCTIONS AND COLONISATIONS You will probably be aware <strong>of</strong> some <strong>of</strong> the flora and fauna that have become extinct in the UK over time, from striking mammals such as wolves, which were wiped out by around 1680, to delicate flowers like summer lady’s tresses, which had disappeared by 1959. However, keeping a close track on losses in recent years is surprisingly difficult. Fewer than 50 species have been declared extinct in the UK since 1970, but this underestimates the true number, because we know so little about much <strong>of</strong> our native wildlife. It is usually easier to detect the arrival <strong>of</strong> a new species than the final disappearance <strong>of</strong> a threatened species. In better studied groups, we know that 1–2% <strong>of</strong> species have been lost from the UK – far too many. Thankfully, very few UK species have become globally extinct: most can still be found elsewhere in their range. However, this is not always the case. One <strong>of</strong> the most high-pr<strong>of</strong>ile global extinctions <strong>of</strong> a UK species involved the great auk, a large flightless seabird that once nested in large colonies on our northern coasts. The species was driven to extinction by the mid-1850s as a result <strong>of</strong> centuries <strong>of</strong> intense human exploitation – it now provides a powerful lesson in just how much damage people can cause. Other lost species include the interrupted brome, a plant which was last recorded in the wild in Cambridgeshire in 1972 (but later reintroduced to three sites). We can only hope that other UK wildlife thought to be globally extinct may yet be found in other places, like the Ivell’s sea anemone, which was only ever known in one lagoon in Sussex. Since 1970, hundreds <strong>of</strong> species previously unknown in the UK have been found here. Some <strong>of</strong> these are long-established members <strong>of</strong> our native wildlife that had simply eluded detection before, such as the Alcathoe bat, which was not found until 2010 1 . Such additions reflect advancements in our understanding and technology, but they do not tell us much about what is happening to our flora and fauna. However, there are a large number <strong>of</strong> species that are new arrivals to the UK, some <strong>of</strong> which have colonised naturally – for example, over 27 species <strong>of</strong> moth have colonised the UK since as recently as 2000, many feeding on non-native plants 2 . Not all colonisers have arrived naturally though. Many new plants, fungi and animals have been imported – either accidentally or deliberately – from all over the world. This process started a long time ago with Neolithic farming; a surprisingly high proportion <strong>of</strong> the UK’s wild flowers, including many <strong>of</strong> our most familiar species such as the common poppy and snowdrop, are “archaeophytes” (introduced pre-1500) or “neophytes” (introduced after 1500). Arable land and brownfield sites are <strong>of</strong>ten dominated by these plants. Whilst many <strong>of</strong> these introductions are harmless, some non-native species have a devastating effect on our native wildlife. The number <strong>of</strong> non-native species arriving as a result <strong>of</strong> human actions is increasing, and their impact on other wildlife is intensifying. Case study Non-native crayfish invasion Signal crayfish The American signal crayfish was introduced to the UK in 1976. As elsewhere in Europe, its appearance resulted in a devastating decline in native crayfish, because it carries a water mould that kills them 3 . It also affected fish stocks and damaged habitat. Another five non-native crayfish species are now found in the wild in the UK, putting further pressure on our native white-clawed crayfish, which has disappeared from much <strong>of</strong> its former range and continues to retreat ahead <strong>of</strong> the northward spread <strong>of</strong> alien species. Some new species have colonised the UK naturally, but many species have been accidentally or deliberately introduced. Case study Starry Breck lichen The rare starry Breck lichen was known in just a few places in the Breckland <strong>of</strong> East Anglia. It was last seen around 2001, and now seems to have disappeared completely 4 . Despite being fully protected by law, this species probably declined because <strong>of</strong> changes in its habitat. Unsuitable grazing and enrichment from nitrogen pollution are thought to have contributed to its demise. These factors still threaten other species in Breckland and throughout the UK – if we do not act, some may go the same way as the starry Breck lichen. MalcolmSchuyl (FLPA) STATE OF NATURE 2013 71