If State of the World, the annual report from the Worldwatch Institute in Washington, is the environmentalist's bible, then Lester R Brown, its founder, is the Old Testament prophet. Meeting him in London for the UK publication of the 1995 report, he was only just off the evening flight from Brussels, where he had been briefing the European Parliament, and before that in Davos at the World Economic Forum.
The tiredness showed, but the missionary zeal was undimmed: "The great issue of our time is re-establishing a stable relationship between the 5.6 billion people in the world and the natural systems and resources on which we depend. Unfortunately, things are becoming more unstable all the timeIwe are winning some battles, but we are still losing this war."
Grand warnings such as these, delivered in a quiet but intense tone, punctuate Lester Brown's conversation, interspersed with a welter of alarming facts and figures: the fish catch from the Black Sea has dropped from nearly 7 million tons a decade ago to 100,000 tons; in the Ivory Coast, export earnings from tropical hardwood forests have fallen from $300 million (Pounds 191 million) a year to just $30 million (Pounds 19.1 million) because, like many other developing countries, it did not practise sustainable forestry; and the sturgeon harvest from the Caspian Sea, once the world's source of caviar, has been reduced to 1 per cent of the level 50 years ago.
Since it first appeared in 1984, State of the World has never made cheerful reading. "We would like to write a positive report," says Lester Brown, almost apologetically, "showing, for example, that world population growth had slowed dramatically, or that carbon emissions were continuing their steady decline. But such a report is not possible."
Lester Brown's environmental career, which has won him many accolades including the 1989 United Nations' Environment Prize and the 1990 World Wide Fund for Nature Gold Medal, began on his father's farm in New Jersey, where he and his younger brother grew and sold tomatoes while still at school. After a degree in agricultural science and six months in India, he became an international agricultural analyst in the US Department of Agriculture and, in 1969, helped establish the Overseas Development Council. In 1974 he founded the Worldwatch Institute, an independent research agency with a staff of 30 based in Washington, dedicated to making information on global environmental issues more accessible.
State of the World is now its chief publication, comprising a large volume of data gathered and analysed by institute staff. The main theme of this year's report is the disastrous effect that destruction of the earth's natural systems - its fish, its forests, even its water - is having on the economic output all over the world. It also includes a paper on the serious threat to world food supplies posed by the population growth in China - 14 million people a year - and a survey of developments in solar and wind power.
"Our main aim is to try to improve the quality of decision-making around the world," says Lester Brown, "whether it is an energy minister in Indonesia, or a couple trying to decide whether or not they should have another child, or wrestling with life-style questions such as whether to use plastic or paper. "
One of the virtues of the institute's approach, he says, is that it is global and interdisciplinary. Environmental, economic and political systems are crucially intertwined, but all too often specialists in one field fail to take account of others.
The yearbook's usefulness has not been overlooked: it is now published in 23 languages and has a first print-run of 100,000 in the US, where it is read by corporation heads as well as in colleges. Almost every college uses it on at least one course, Lester Brown says, and it is also used in some high schools. Its influence percolates down to younger children: it helped, for instance, to inspire the cable television entrepreneur, Ted Turner, to produce the highly successful "green" cartoon, Captain Planet and the Planeteers.
"Ted and I were talking about how we had reached the point when there simply wasn't time to train a generation of teachers, who would then educate a generation of students, who would then become decision-makers.
"If we followed that route, time would run out. So Ted's idea was to go to the kids directly, through a cartoon series."
Again underlining the urgency of the task, Lester Brown adds: "We are the first generation whose actions will quite literally shape the future habitability of the planet. No other generation has had the capacity to do that."
There has, however, been some progress, notably the phasing out of chlorofluorocarbon (CFC) emissions damaging to the ozone layer, which have been reduced by 60 per cent since 1985. But although a sizeable step forward, it was a relatively easy one, he says, since it was neither too difficult nor too costly to develop alternatives to CFCs. Getting nations to move on the two most critical issues - stabilising the climate and curbing population growth - is far more problematic.
On the first question, Lester Brown believes a shift from a fossil-fuel-based global economy to a solarhydrogen-based one could be technically possible within a few decades, although there is not yet the political will for it. The recent flooding in northern Europe may not have been a direct result of global warming, he says, but is nevertheless the sort of extreme climatic behaviour that will become more common as global warming proceeds.
"When you get more energy in the system, a few more degrees can generate an enormous difference in storm intensity, drought or flooding. The earth is only 7degF warmer than at the peak of the last Ice Age - not very much in degrees, but huge in terms of the effect on the system."
As for population growth, Lester Brown castigates political leaders for barely raising the subject. "It is not a question of whether a couple can afford more than two children, it's a case of can the planet afford it? I think the answer is probably not. Political leaders ought to be saying that."
Young people, he believes, are genuinely concerned about environmental problems. "My impression is that they sense more clearly that it's their future that is at stake." But they need more guidance, more education. Getting involved with single-issue projects, such as recycling, as many of them do, is not a bad start. "The downside is that they can end up thinking that's it. It's important, but it's only part of what is needed."
Studying a local eco-system, such as a pond or woodland, is something most schools in this country do from the infants upwards, and is a useful way of developing children's understanding of natural processes and cycles, Lester Brown says, "giving them a sense that we are a part of nature, not apart from it".
State of the World itself is already picked up by "all serious geography departments" in secondary schools here, according to Graham Ranger, education secretary of the Geographical Association, because of its new data and often provocative points of view. But its format - densely informative articles which do not lend themselves well to maps or graphics - means teachers "have to do some work on it" before it is useful in the classroom.
Concepts like "sustainable development" and "biodiversity" may be watchwords of a publication like State of the World, but are only just beginning to make their way into British geography syllabuses and textbooks, Mr Ranger says. Climatic change has been taught for a long time, he says, but population has tended to be approached mechanically, in terms of birth and death-rates. Looking at the problems of population growth, or the idea of sustainability, can be taxing for teachers.
"There can be difficulties in turning conceptual subjects such as these into learning activities. And teachers need considerable support because it can feel quite threatening to them; they maybe lack the confidence to tackle global question where they can't provide answers.
"Pupils also may find these things threatening, but I think they do cope, as long as it is taught on their level."
And what of Lester Brown himself; doesn't he ever find it threatening, or even depressing, to battle against such huge and daunting questions every day of his life?
"People often ask me if I'm an optimist or a pessimist", he replies, with a gentle smile. "I think I must be a congenital optimist to have been doing this work for 20 years".
He does admit, though, that it was a pleasant relief recently to spend some time with his daughter, a vet in Colorado, helping her inoculate heifers and treat sick dogs. Here at least was the satisfaction of problems that could be fixed - and quickly, too.
State of the World 1995, Pounds 12.95. Earthscan Publications, 120 Pentonville Road, London, N1 9JN.