Mathematical modelling to protect native species

For nearly 10,000 years the red squirrel has been a part of the UK's natural heritage. Previously widespread across the country, our only native species of squirrel is now under serious threat of extinction, its numbers having declined dramatically since the 1950's, plummeting from around 3.5 million to around 140,000 today.

Native species are a critical part of biodiversity and the demise of the red squirrel gives much cause for concern. The impact of grey squirrels – introduced by the Victorians from North America – has been catastrophic for the reds. Acting as fatal carriers of squirrelpox, but immune to the virus themselves, the greys have devastated the red squirrel population which, with no immunity to the virus, has quickly succumbed to the disease.  

There is an economic impact as well: it is estimated that the invasion of grey squirrels have cost the British economy £14million per annum (The Economic Cost of Invasive Non-Native Species on Great Britain. CABI, 2010, VM10066).

Without conservation management red squirrels are likely to disappear from the UK mainland altogether, but their conservation is a complex matter. Mathematical modelling research, led by Professor Andy White at Heriot-Watt's Maxwell Institute, is helping to influence practical methods that could stem the tide of the species' decline.

Shaping conservation and forest management strategies to protect red squirrels

Professor White's work has had direct impact on policy decisions to protect red squirrels in Scotland – including incorporation into the Scottish Strategy for Red Squirrel Conservation – and has influenced management practice employed by conservation agencies, such as the Red Squirrel Survival Trust which works to protect red squirrels on Anglesey, Wales. 

The modelling research has also been extended to answer specific red squirrel conservation issues faced by forest management practitioners, and provides an exemplar of how modelling can help managers objectively balance the differing pressures of multipurpose forestry. It underpinned a special report prepared for Forestry Commission Scotland to provide advice and guidance for the management of red squirrel populations exposed to squirrelpox virus, and was used as the template for the red squirrel conservation strategy adopted on the national forest estate in Dumfries and Galloway.

Broadening understanding of the processes underlying ecological invasions

Professor White's work is demonstrating how mathematical modelling techniques, which include a realistic representation of the heterogeneous spatial structure of natural systems, can inform and help direct conservation strategies to protect endangered species.
His team's research, which employs deterministic and stochastic mathematical modelling, was the first to show that squirrelpox accelerates the process of replacement, and that disease was a clear causative factor in the decline of red squirrels in the UK. It also provided information on the predicted spread of squirrelpox throughout Scotland, and demonstrated that the exclusion of grey squirrels – from protected ‘stronghold' regions that support populations of red squirrels – was sufficient to protect reds from replacement. 

Ecological modelling focusses on the use of mathematical models to understand ecological processes and ecosystem function, and Professor White's research is broadening understanding of the processes underlying ecological invasions, ultimately leading to more robust conservation practice.