A growing concern

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Having started out as a practical forester with an interest in ecology, John Jeffers found himself increasingly involved in statistics as a way of making

sense of the world. His career led him ultimately to the planning and man-

agement of ecological research, and the monitoring of change in the British

landscape, including the extent of fallout from the Chernobyl accident.

those days, there were very few of the bed-and-breakfast establishments that are now so com-mon everywhere. We were paid a special subsist-ence allowance on top of our normal salary, but this was not enough to cover the cost of staying in hotels, except for the odd night in order to make sure of getting a bath.

The sample plot party travelled to every county of England, Scotland and Wales, provid-ing a unique knowledge of the British country-side and its forests. It was an opportunity to experience living in rural communities and to learn something of their concerns at that time, and it was also perhaps the best introduction to British forestry that it was possible for a young man to have.

Discovering statistics

For 2 months of each winter, the sample plot party came into the main research station at Al-ice Holt in Hampshire to work up the measure-ments collected during the year. It was during these periods of intensive calculation that I was introduced to methods of mathematical statistics that stimulated my interest in characterising the growth of forests from the careful measurements that we were making in the fi eld. It was an in-terest that grew as I read more and more about statistical theory and methods, and which led, over a period of several years, to my being trans-ferred to working full time on the design and analysis of forestry experiments. Subsequently, I took the examinations of the Institute of Statis-ticians, passed the Civil Service Limited Competi-tion to the Statistician Class, worked briefl y for the Ministry of Agriculture, Fisheries and Food,

I left school at 16 to join the Forestry Commis-sion, fi rst as a forestry apprentice for 1 year in the New Forest, and then for a 2-year training course at the Benmore Forester Training School in Argyll. I had worked at two wartime forestry camps run by the Scouts and greatly enjoyed the physical work in the woods, but I was also strong-ly infl uenced by an introduction to ecology from my headmaster during my last year at school. He had stimulated my interest in the interactions be-tween organisms and their environment and the countryside generally. Forestry seemed to be an ideal career in which to pursue that interest.

Introduction to research

At the end of my 2-year course of practical for-estry training, I was appointed to the sample plot party of the Forestry Commission Research Branch. Between the two World Wars, the For-estry Commission established a series of perma-nent sample plots in plantations of a wide range of different species and on an equally wide range of habitats across England, Wales and Scotland. By measuring the trees on these plots regularly, usually every 3 years, we intended to build up our experience of tree growth and volume, in or-der to improve the management of the forests and the choice of the most appropriate species for individual sites. The work of the sample plot party entailed a semi-nomadic existence during the spring, summer and autumn of each year. We travelled from plot to plot by truck and then looked for somewhere to live for the week or two that we would be in that area, usually by asking at the local post offi ce if they knew anyone who might let rooms for some or all of our party. In

“The whole Chernobyl episode illustrated the value of a simple

survey, soundly based statistically, and exploiting available expertise

and equipment”

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determining the structure, composition and processes of terrestrial ecological systems and the abundance and performance of individual species and organisms. This research was re-quired to provide a sounder scientifi c basis for predicting and modelling future environmental trends, and especially those resulting from hu-man activities.

The need to monitor change in the coun-tryside was an obvious priority. While with the Forestry Commission, I had been involved in a discussion on the feasibility of a census of Brit-ain’s rural land and I remembered a comment by Frank Yates, the principal statistician at Roth-amsted Experimental Station and one of the originators of modern survey design, that the monitoring of change in the countryside was impossible without a sound basis for the strati-fi cation of the whole landscape. Stratifi cation is a statistical device whereby the variability of a population is reduced in order to improve the precision of estimates that are derived from samples.

“The monitoring of change in the countryside was impossible without a sound basis for the stratifi cation of the whole landscape”

One of ITE’s fi rst research objectives, there-fore, was to explore possible ways of stratifying rural land in order to improve the precision of sample surveys. At the Forestry Commission I had used a technique called association analysis as a means of analysing large amounts of survey data, and I had written the necessary computer programs for the analysis. ITE’s scientists were already engaged in a survey of woodlands and, after some initial trials, had begun an extensive survey of Cumbria, based on a sample of 1 km squares. They collected a large number of map-based data for each of these sample squares, including the presence or absence of almost all of the features shown on a 1-inch Ordnance Sur-vey map. The analysis of these data suggested a classifi cation of the land area of Cumbria into 16 main types which, when examined in detail, looked extremely promising as a preliminary stratifi cation for sampling.

Grid squares with similar features came to-gether in this classifi cation in such a way that there was less variability within each of the 16 types than in the total set of sample grids. Fur-thermore, on the basis of the principal charac-teristics identifi ed by the classifi cation, it was possible to assign any other grid square to one of these 16 main types.

The result of the Cumbria exercise suggested that it would be feasible to extend the classifi -cation to the whole of England, Wales and Scot-land, and a new set of 1 km grid squares was selected as a systematic sample representing this larger population. The outcome was even

Monitoring landscape change

However, a further major change in my career occurred in 1968 when I was appointed as Direc-tor of one of the Nature Conservancy’s research stations. Then, in 1972, I was made Deputy Director, and then Director, of the Institute of Terrestrial Ecology (ITE) which was created with the reorganisation of the research activities of the Nature Conservancy. My concern now was with an improved understanding of the factors

and then was appointed as Principal Statistician to the Forestry Commission Research Branch. There followed a period of intense activity during which the research of the Forestry Commission developed rapidly, and during which we became one of the fi rst forest research organisations in the world to acquire our own electronic compu-ter. This opened up the scope of our research possibilities and greatly increased our access to more powerful methods of data collection and analysis.

Measuring standing sample trees with the permanent sample plot party in 1946


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better than we had hoped, eventually produc-ing a classifi cation of grid squares into 32 main types. The resulting ITE Land Classifi cation later became the basis for much of the research that we did on land use change, including a survey of agricultural land across Britain as a whole. Sur-prisingly, this approach was heavily criticised by other scientists, and even as late as the end of the 1980s there were colleagues who were un-able to see the value of an ecologically based stratifi cation for the purposes of understanding and prediction.

There had been several previous attempts at countryside surveys, but they had all failed be-cause of the lack of a sound statistical base, but it was now possible to complete such a survey on a stratifi ed random sample of grid squares from Britain as a whole. The fi rst completed survey, in 1978, looked at vegetation and soils, and subse-quent surveys in 1984 and 1990 added assess-ments of land cover (using both remote sens-ing and ground surveys), linear features such as hedgerows and fi eld boundaries, and the state of freshwater conditions in lakes, rivers and streams. Further repeated surveys have contin-ued to reveal the changing face of the British landscape.

Chernobyl depositions

Among the earliest infl uences on the ITE research programme was the need to monitor the distri-bution of radionuclides, initially the fallout from international atom bomb tests. As a result, a new “clean” radionuclide laboratory was set up in the Merlewood Research Station in Cumbria. Fieldwork on radionuclide monitoring also began around ex-isting nuclear reactors and power stations.

However, the most important extension of this research occurred after the Chernobyl disas-

land and in North Wales were suffi ciently high for precautions to be necessary. I received a se-vere reprimand for passing that information to the Ministry of Agriculture, but I was more con-cerned to know that the appropriate precautions had been set in motion. The Ministry then took the necessary precautions and some of these ar-eas are still under strict control today.

The whole Chernobyl episode illustrated the value of a simple survey, soundly based statis-tically, and exploiting available expertise and equipment. The survey revealed that there were only a few places in the UK where depositions of radioactive caesium from Chernobyl on grass-land were suffi ciently serious for precautions to be taken against the risk of contamination of the human food chain. The results were, in fact, highly encouraging and served to reduce the fears of the public that had been grossly exag-gerated by unnecessary secrecy. There were sim-ilar depositions on woodlands and heathlands, and I regret that we were unable to convince any agency to fund a survey of these habitats. The outcome of the Chernobyl accident was the addition of an easily recognised source and quantity of radioactivity to complex ecologi-cal systems. We should have taken advantage of that situation to determine the subsequent pathways and decay of the radioactivity, but the dependence of research on the funding of short-term projects made such an initiative im-possible.

“With the growing recognition that the natural resources of our world are being depleted at a rate that is unsustainable, there is an urgent need for scientists to monitor and, if possible, to predict the changes that are taking place in our world”

With the growing recognition that the natu-ral resources of our world are being depleted at a rate that is unsustainable, there is an urgent need for scientists to monitor and, if possible, to predict the changes that are taking place in our world. Statisticians have a crucially im-portant role to play in guiding the collection of the information necessary to monitor these changes and to understand the complexity of the world’s economic, social and ecological systems. Much of the popular emphasis today is on the analysis of data, but good design of the initial data collection is an essential pre-requisite for valid analysis and interpretation. The international nature of this challenge offers today’s young statisticians an exciting and ful-fi lling opportunity.

Where has statistics taken you? If you would like to tell your personal statistical story, please e-mail signifi [email protected].

ter in April 1986. Warned by colleagues in other countries that there had been a sudden increase in levels of radioactivity in their environments, ITE staff collected samples from the high fells of the Lake District during the weekend after the announcement of the disaster in the Ukraine. To our surprise, we found very high levels of two isotopes of caesium in these samples, in pro-portions that identifi ed the distinct footprint of Chernobyl radioactivity.

As the most likely pathway of radioactive caesium to humans was through animals grazing on grass pastures, I decided to initiate an im-mediate survey of grassland throughout Britain. We had the necessary expertise and equipment, and could also organise the collection of sam-ples through the wide geographical distribution of ITE’s research stations. Even more importantly, we could design a very effi cient sample survey by using the stratifi cation provided by our land classifi cation.

Interestingly, I was instructed to stop the survey when the government heard that we had embarked on it. However, it was an instruction I chose to ignore, and several weeks later I was asked whether, by chance, the survey had gone ahead as there was now national interest in the results. We were, in fact, able to pinpoint very accurately where there had been signifi cant depositions of radioactive caesium on grass-lands in the UK. However, the government be-came very sensitive to any suggestion that we might tell members of the public or the media anything that might reveal the results of our surveys.

I was especially concerned that no measures were being taken to prevent sheep from critical areas, where there were very high levels of cae-sium depositions from Chernobyl, entering the human food chain. Depositions in parts of the Lake District, in the Southern Uplands of Scot-


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