Life in the Undergrowth uses the latest photographic technology to reveal the previously unseen workings of a strange and often spectacularly beautiful world that underlies our own. "If you lost ants and millipedes and earthworms, the ecosystems would collapse before you knew where you were," Sir David Attenborough says.
"They pollinate the flowers, they provide food for a great number of vertebrates - reptiles and mammals and so on - they fertilise the soil, they turn over the soil, they get rid of dung, they are the basic foundations."
Most people know that insects are invertebrates but, as Sir David points out, not all invertebrates are insects. "Insects have just six legs, and there are lots of things in the undergrowth that have more than that - centipedes, millipedes and spiders and so on.
"They were the first animals by several hundred million years to get on the surface of the land; they colonised the land from the sea long before any of our ancestors did. They are in consequence the basis of every ecosystem."
Over the last 20 years Sir David has made TV series about birds, mammals, the oceans, plants, fossils and man. "The one thing missing is a series about amphibians and reptiles, and we're working on that at the moment, but it's at least another two years down the line. And that will be the set!" But why has it taken so long to get round to the invertebrates?
One reason, he says, is because being small, they are hard to film. But new electronic cameras have made it easier. "If you are trying to get any depth of focus on, say, a spider, you may have to throw so much light on it that you fry the poor thing. You certainly don't allow it to behave in a normal fashion. But new optical gear enables us to film them better than we've ever done before."
At the end of each of the series' five programmes, there is a 10-minute section, co-produced by the Open University, which explains how some of the images were captured. Emerging butterflies, courting damselflies, ants milking aphids and what earwigs get up to at night are just a few of the fascinating sights uncovered by the hi-tech cameras.
And it's fascination that is the key to Sir David's extraordinarily successful approach to making wildlife programmes over the last 50 years. "The reason I make natural history programmes is because I am fascinated by the natural world. I think for a lot of people one of the great pleasures of being alive is trying to find out about the natural world and understanding the way it works. I have an extraordinary number of letters from people whose lives have been illuminated, during good times and bad, by contemplation of the natural world."
How optimistic is he about the future of the natural environment? "It's difficult to give a succinct answer," he says. "The hopeful thing is that more people and more politicians are aware of the dangers that face us all. From that point of view there is some reason to think that maybe we will get our act together and clean up the seas and the air.
"Against that is the fact that the problem itself is much greater. The population of the world has doubled since I was born. Nearly all these problems arise from density of population. People want more and more food and they want more and more commodities. I am sure the earth is going to have fewer species in years to come than it does now.
"If you said, 'OK, it doesn't matter, we won't bother about that', you'd lose much more than if you spent a great deal of time going around saying, 'Do you realise what we're doing?'."
His favoured approach to conveying environmental messages to the viewer is, however, a subtle one. "My own view is that it would be a disaster if every natural history programme was a conservation programme. Of course there must be, and there are, programmes about ecology and about climate change and the loss of species in general. But if they were all like that, you would be throwing out the baby with the bath water.
"I'm not grinding an axe, I'm doing it because I think it is one of the great pleasures in life. Nobody is going to save whales unless they know what whales are and why they are amazing."
The popular OU/BBC2 programme Rough Science returns this week for its sixth series, with presenter Kate Humble. Filmed among the spectacular peaks of Colorado's Rocky Mountains, the science and ingenuity show sees plucky boffins Mike Bullivant, Jonathan Hare, Ellen McCallie and newcomer Hermione Cockburn tackle a series of scientific and physical challenges at 3,000m, using the rich natural resources of the region.
For the new series the Open University has produced a set of Science Survival Cards available free to viewers who do want to try it at home - subjects include generating your own electricity, making your own sun block and producing safe drinking water. Rough Science is due to be broadcast on BBC2 at 7.30pm on Wednesdays, starting from 2 November.
John Windell's interview was first published in 'ozone', the OU listings magazine. 'Life in the Undergrowth' is due to be broadcast on BBC 1 starting on Wednesday 23 November. Check listings for details.
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