Young people "know less and care less" about the natural environment than older age groups, Alastair Lavery of the Royal Society for the Protection of Birds told the conference.
Studies for the society show that 44 per cent of 16-24s could recognise a house sparrow, against 65 per cent of those over 55. When asked where swallows go in winter, 46 per cent of 11-14s said they flew to Africa, against 72 per cent of those over 55.
Knowledge about the birds, bees and much else increases steadily with age, suggesting that some things have changed radically in recent decades. When asked whether learning about nature is time well spent, 49 per cent of under-31s said it was, in contrast to 85 per cent of those over 60.
Dr Lavery, chair of the sustainable development education liaison group, said a study from the United States, likely to be replicated here, showed that in 1981 the average time primary children spent out of doors each day was 86 minutes: this had shrunk to 42 minutes by 1997.
While young people's pattern of daily life was changing, so was the approach to outdoor education. In 1982, there were 163 residential providers, against 60 to 70 in 2000. Similarly, in 1979 there were 45 full-time equivalent teachers with a formal outdoor education remit in one local authority, against seven in 1999.
Dr Lavery lamented the lack of precise Scottish statistical evidence but said his "gut feeling" was that schools had lost opportunities to bring young people into contact with the natural world.
Don Ledingham, acting head of education in East Lothian and a former physical education teacher, said planning around A Curriculum for Excellence presented the most exciting opportunities for schools since the 1960s. "It is critical we do not blow it," Mr Ledingham said. Outdoor learning had to "get away from the image of the bad boys trip" and be available for all. It had to draw in all teachers to be sustainable and not just the specialists.
At Dunbar Grammar, 90 pupils were doing the Duke of Edinburgh Award Scheme, all first-year pupils went away for a residential experience, all 700 pupils walked two miles to a barbecue in John Muir Country Park and groups picked up litter locally.
A group of 25 are travelling again to California to walk in the footsteps of Muir in Yosemite National Park and re-establish the link with Muir's birthplace in Dunbar. Muir was the pioneer of the environmental movement early last century.