One in five British mammal species face a high risk of extinction, according to a report that involved data analysis by the Centre for Ecology & Hydrology.
The study, led by The Mammal Society, is the first comprehensive review of mammal populations for more than 20 years.
It has produced the first approved “Red List” for native British Mammals, highlighting species that are at risk of extinction within the next 10 years. The wildcat, greater mouse-eared bat and black rat are considered the most endangered species, while the Society says urgent action is also needed to save the red squirrel, water vole and grey long-eared bat.
Mammals such as the hedgehog and water vole have seen their populations reduced by up to about 70% in the past 20 years.
Loss of habitat through development and agricultural practices, use of pesticides and road deaths are all putting pressure on these species, according to the report, and its authors hope it will help prioritise conservation actions and set an agenda for future research efforts.
Dr Colin Harrower, a Spatial Data Analyst at the Centre for Ecology & Hydrology (CEH), was a co-author of the report, Review of the Population and Conservation Status of British Mammals. He analysed data from more than 1.5 million reported sightings of 58 terrestrial mammal species spanning 22 years (1995-2016).
There were a number of sources of sightings, including information from the Biological Records Centre (BRC), which is run by CEH, and data from wildlife groups.
Dr Harrower then used the sightings from England, Scotland and Wales to produce estimated ranges for each species.
The estimated ranges were then linked to habitat types using CEH’s Land Cover Map 2007, which maps out broad habitat across the UK, to determine the areas of each habitat within the species range. The areas of each habitat were then multiplied by density projections – pre-determined estimates of population of a species in each certain type of broad habitat – to give total numbers.
The study found that the geographical ranges of 18 species have increased since 1995, four have declined and 22 have remained stable. A lack of data prevented assessment of the remaining 14 species. The species that have increased their geographical range since 1995 included otter, pine marten and polecat; red, fallow and roe deer; the greater and lesser horseshoe bat; and beaver and wild boar.
Dr Harrower said: “A key aspect of the Centre for Ecology & Hydrology’s remit is to measure and explain the causes of long-term, large-scale changes in animal and plant populations.
“CEH worked in partnership with the Mammal Society to analyse data to provide up-to-date estimates of geographic distribution and trends for terrestrial mammal populations in Britain.
“Records obtained from the public through citizen science activities are a key resource and were crucial to this study. This includes members of the public going out for a walk who can - via an app such as Mammal Tracker - record what species they see, when and where.”
Following the study, which was funded by Natural England, Natural Resources Wales and Scottish Natural Heritage, The Mammal Society is now calling for more research to be carried out urgently to get a clearer and more accurate picture of Britain’s mammal populations.
CEH scientist Prof Richard Shore, who is chair of the Mammal Society’s Scientific Advisory Committee and was a co-author the report, said: “The information that the report presents provides a key tool for assessing conservation status. It gives us more confidence about the distribution of species in terms of geographical location and habitat.”
“The report also flags the uncertainties around the population estimates and trends, highlighting where our knowledge is poor and further study is needed.”
There were sightings from practically every area in Britain. The most frequently sighted species was hedgehog (more than 140,000 sightings from 1995-2016), followed by rabbit, grey squirrel and fox (at least 100,000 sightings each).
The rarest mammal in terms of number of sightings were Orkney vole, Alcathoe whiskered bat, black rat, lesser white-toothed shew (less than 100 each). The most widely distributed species was rabbit, closely followed by hedgehog, otter, mole and fox.
The historic comparison for data were The Atlas of Mammals in Britain (1993) by the Institute of Terrestrial Ecology, a forerunner of CEH, for distribution and the 1995 Harris Report for population numbers.