Derek Ratcliffe

Conservationist who identified the harmful effects of pesticides on birds of prey

Derek Almey Ratcliffe, ecologist and science director: born London 9 July 1929; field staff, Nature Conservancy (later Nature Conservancy Council) 1956-70, Deputy Director (Science) 1970-73, Chief Scientist 1973-89; married 1978 Jeannette Chan-Mo; died Newcastle upon Tyne 23 May 2005.

Derek Ratcliffe was the outstanding field naturalist and conservationist of his generation. No one in Britain, quite possibly in Europe, matched his knowledge and expertise over so broad a range, from birds and mountain vegetation to the ecology of bogs and the biogeography of mosses and ferns. His contributions to field study were matched by his record as a government scientist who made a major contribution to the policy and practice of nature conservation in Britain during the second half of the 20th century.

Above all, he will be remembered for his pioneering work on the effects of pesticides on birds of prey. His survey of the peregrine falcon in 1961-62 for the British Trust for Ornithology was ostensibly to provide facts and figures to the Home Office. Pigeon fanciers had complained that the falcon's appetite for racing pigeons was ruining their sport, and petitioned the Home Secretary to remove legal protection from the species. However Ratcliffe and his volunteer surveyors found that the peregrine was in fact in rapid decline. By 1963 its numbers had fallen to below half of their pre-war level and it had ceased to breed in southern England and most of Wales.

Early on in the survey, Ratcliffe discovered a nest with addled eggs and sent one to a government laboratory for analysis. The egg contained high levels of pesticide residues. Ratcliffe had a hunch that pesticides were responsible for the large number of broken eggs he was finding. Using his friend Desmond Nethersole-Thompson's contacts, he was able to investigate numerous egg collections and, by comparing the weight of eggs past and present, determine that the shells had grown thinner and so were more prone to breaking.

His meticulous study provided the most detailed evidence of the effect of persistent pesticides like DDT and dieldrin on wildlife. Ratcliffe's short paper in Nature in 1967, followed by a detailed one in the Journal of Applied Ecology in 1970, must be among the most quoted in ecological science. They led to hundreds of follow-up studies worldwide which demonstrated how pesticides were seriously reducing the breeding performance of birds without killing them outright.

Ratcliffe extended his studies of eggshells to the golden eagle, which was suffering from the "sublethal" effects of the pesticide dieldrin, then used in sheep-dips. His work helped convince the Commons Advisory Committee on Pesticides to recommend restrictions on the most damaging agricultural pesticides. As a result, birds of prey, including the peregrine, began to recover. Today there are more peregrines nesting in Britain than at any time during the last century, and they are even colonising cities.

In 1965, Ratcliffe masterminded a grand inventory of Britain's wildlife and wild habitats. Like the peregrine survey, it began with a limited set of aims, but under Ratcliffe's direction broadened out into something much more ambitious. To justify its programme of nature-reserve acquisition, the Nature Conservancy was asked by government to prepare a "shopping list" of places it needed to complete a representative series of protected habitats. Ratcliffe used the opportunity to explore the flora and fauna of little-known parts of Britain.

He developed a method for comparing one place with another and evaluating their importance. Using criteria such as extent (the bigger the site, the greater the diversity), "naturalness", "fragility" and "typicalness", he in effect discovered which places are the most important for wildlife and so deserving of protection. Completed by 1970, A Nature Conservation Review was the most thorough survey of Britain's wild places ever made. It became the cornerstone of the Nature Conservancy's policy of site selection. But, worried about the implied costs, the Treasury delayed publication of the review until 1977.

Derek Ratcliffe was born in London in 1929, the son of a cinema pianist and a teacher of French and English. His first experiences of wandering "where the wild creatures and plants drew me" was in London's parks and green spaces, and on his grandfather's farm near Cromer in Norfolk. In 1938 the family moved to Carlisle, where Ratcliffe was a pupil at Carlisle Grammar School. The shy, usually silent boy also began to attend Carlisle's active Natural History Society, which somehow managed to keep going throughout the Second World War.

He met his lifelong mentor there in the person of Ernest Blezard, the curator of natural history at Tullie House Museum. Blezard was an all-round field naturalist with an encyclopaedic knowledge, especially of upland birds. He taught the young Ratcliffe to make meticulous and accurate field records, and also instilled in him a strong sense of public duty. Beneath his quiet persona, Ratcliffe was a restless, energetic youth with an unquenchable thirst for field exploration. He became an avid nest-finder, and hence a fearless climber of trees and crags. However he was not a collector; his purpose was to inspect a nest, not to loot it.

In 1947 Ratcliffe won a City Corporation scholarship to study Zoology at Sheffield University. Soon bored by anatomy and dissections, he switched to Botany, which, under the influence of Professor Roy Clapham, offered more scope for field study. After graduating with a first class degree, Ratcliffe won a Nature Conservancy bursary to study hill vegetation. Based at University College, Bangor, where his tutor was the like-minded Paul Richards, Ratcliffe was in his element, using techniques pioneered in Scandinavia to study the natural patterns of plant communities and the way they relate to rock, soil and water.

On weekends off, he went hunting for ferns and mosses with his fellow researcher, Reg Parker. Having acquired a plate camera in 1947, Ratcliffe became a skilled natural history photographer. In 1956 he was awarded a PhD and simultaneously offered a job with the Nature Conservancy.

Ratcliffe completed his National Service in the Royal Army Education Corps at Catterick, where he took charge of the local field club. In 1958 he resumed his studies of hill vegetation, this time as a member of the conservancy's field staff based in Edinburgh. With Donald McVean, his formidable task was to describe and classify natural vegetation in Scotland. At that time Ratcliffe had not even passed his driving test, and so had to move about the Highlands by train and bicycle.

The survey, Plant Communities of the Scottish Highlands: a study of Scottish mountain, moorland and forest vegetation, based on thousands of sample plots all over the Scottish uplands, was published in 1962. The work for the first time made it possible to compare Scotland's wild vegetation with that of Scandinavia and Central Europe. By then, Ratcliffe was perhaps the best-travelled hill naturalist in Britain, able to spot a distant raven's nest by the tell-tale stain on the rock, or find rare alpine plants in remote places no other botanist had yet ventured.

Ratcliffe made his reputation in the 1960s with his contribution to pesticide research and the Nature Conservation Review. His promotion to Deputy Scientific Director at the age of 40 was recognition of his rare versatility as a field ecologist. Three years later, Ratcliffe became Chief Scientist of a reorganised and now purely administrative Nature Conservancy Council (NCC). His job was to oversee a programme of commissioned research with the help of a team of specialists. As the effective number two in the NCC, he also had a say in policy.

Having no great appetite for day-to-day administration (for which he found a deputy), Ratcliffe made his most lasting contribution in stiffening the NCC's backbone to take on vested interests that were destroying wild places. Convinced that nature conservation was doomed to fail if it forever fought rearguard actions, he pushed for a more confident approach. For example, he persuaded the NCC's chairman, William Wilkinson, to criticise the wholesale afforestation of the uplands, thereby precipitating a memorable battle with the powerful forestry lobby in the 1980s.

With his capacity for analysis, Ratcliffe developed the arguments which persuaded politicians to compromise over the afforestation of the "Flow Country" of Sutherland and Caithness. He also led the NCC to champion nature as a "cultural" as well as a scientific asset. The climate has changed so much since then that it is hard to imagine that at the time this was seen as a radical statement.

Although Ratcliffe received numerous national and international awards, he was never honoured by the state. It was widely expected that he would be elected FRS and at least appointed CBE after his retirement in 1989. Probably his outspokenness was held against him. The Times, at least, included him in a list of the century's most influential voices, mainly on the strength of his work on pesticides and habitat evaluation. In retirement Ratcliffe remained active, serving as Vice-President of Plantlife and the British Association of Nature Conservationists, and as an editor of the Collins New Naturalist library.

He also wrote books, including Bird Life of Mountain and Upland (1990), The Raven (1997) and Lakeland (2002), as well as a new edition of his classic book The Peregrine Falcon (1993). His writing was clear, wide-ranging and based on personal observation. His recall of field records was phenomenal. The detailed notes on the excursions of his youth in his memoir In Search of Nature (2000) relied almost entirely on memory.

In retirement, Ratcliffe and his wife, Jeannette, would set off each May to Lapland to study and photograph breeding birds. Ratcliffe had long wanted to observe the summer habitats and behaviour of birds that only winter in Britain. After a dozen seasons near the Arctic Circle, he felt ready to write Lapland: a natural history, which is due for publication in August. He was setting out for another northern expedition when he suffered a fatal heart attack.

Peter Marren