A UNIQUE conservation plan is under way in Kielder forest to prevent England's biggest surviving population of red squirrels from dying out in 11 years' time from a lack of food.

The forest district, where 150m trees span 200 square miles from County Durham to the Scottish border, is one of the few places in Britain where the native red squirrel is still abundant.

Numbers have been declining on a national scale for 125 years - ever since the grey squirrel was introduced into this country - and in 1995 the government listed it as a priority species for conservation.

Researchers from Newcastle university, working with Forest Enterprise which manages Kielder, have helped foresters to redesign the layout of a conservation area which will ensure native squirrels have adequate food and survive for at least the next 40 years.

Forest Enterprise is the management agency of the Forestry Commission, and the plan has the backing of neighbouring private landowners. The Newcastle team hopes to receive support to expand the work to the rest of Kielder district.

Survival of the species as a whole depends on careful management of the forest habitat, and the work has the potential to be applied to conservation areas for squirrels and other endangered species.

Wildlife experts estimate that up to 10,000 native red squirrels live in Kielder forest - England's biggest forest and one of the largest man-made commercial forests in Europe.

They are an added attraction for the half a million visitors to Kielder each year where up to a third of local people work in the tourism industry.

Under the red squirrel action plan, one area, Spadeadam forest, has already been designated as a squirrel conservation area.

University ecologists from the Centre for Life Sciences Modelling have assessed the layout for a similar project at Kidland forest, where several hundred of the animals are said to live.

They found that a felling and design plan which Forest Enterprise was replacing would have drastically reduced food supplies for the squirrels.

The centre, which has an international reputation for expertise in the application of computer models for introduced or endangered species management, developed a computer population model for the squirrels. It is simulates the impact of proposed felling and restocking plans on red squirrel viability.

This work is the culmination of ten years of field and modelling work on red and grey squirrels, and was made possible by the recent introduction of geographic information systems in forest management which hold forest design and felling plans in digitised format.

The 2050-hectare Kidland Forest within Northumberland's Cheviot Hills is considered to be an ideal conservation area for the threatened red squirrel - it is isolated and inaccessible for grey squirrels now colonising Northumberland.

The joint project assessed the suitability of Kidland for red squirrels over the next 40 years, and showed that the felling proposed in the previous design plan for Kidland forest would have removed large amounts of the main source of food for the squirrels - the seeds found in conifer cones.

Harvesting and replanting of timber is part of the normal cycle in a forest. The harvesting of timber is carried out on rotation and the life-expectancy of a plantation depends on the type of tree, the soil and the wind-throw hazard - older trees are at risk of being blown down by strong winds which rip their shallow roots out of the peaty forest soil.

Suggested plans to replace the felled trees with oak in parts of Kidland forest would also have affected the survival of the red squirrel. Broadleaf trees are a source of food for the grey squirrel which can out-compete and replace native reds.

The new forest design involves keeping more mature trees and planting a greater variety of conifers. Plans to plant oak trees have been switched to another area of the forest to ensure grey squirrels cannot replace the reds at Kidland should they get there.

Dr Lurz said: "The availability of a suitable habitat is a key resource determining the presence of a species in a particular landscape.

"When red squirrel population dynamics were simulated based on the current forest composition, the felling plan and possible tree seed compositions, the results indicated that red squirrels in Kidland could be reduced to a handful, fewer than 20, and face local extinction around 2012."

"This would be caused by the reduction in suitable habitat of cone-bearing age over the next 20 years due to timber harvesting.

"If oak trees were planted and allowed to mature, the grey squirrel population was predicted to expand and to reach an average of 80 individuals by 2050.

But he added: "The simulation results of the revised felling and restock plans indicate that red squirrels should persist for the next 40 years until the next rotation"

The development of computer models for native mammals such as the red squirrel and the availability of high quality forest maps or satellite images provides a unique opportunity for the conservation of endangered native mammals.

Mr Graham Gill, forest manager of Kielder district said: "The Newcastle university work has given us a much-improved understanding of the habitat requirements of red squirrels which we are able to put to immediate effect in our redesign of Kidland forest.

"Large conifer forests like Kielder and Kidland are rapidly becoming the last refuge of red squirrels in England, and the decisions we take today have direct influence on the squirrel populations of 40 years in the future.

"Our new forest design plan does not offer any guarantees, but should help tip the balance a little more in this cherished animal's favour.