A young South African man was talking to a woman selling fruit in the main street of a northern Tanzanian village. 'Do you think you could make one of these?', he asked in rapid Swahili, holding up a lidded box, a simple frame covered with woven banana leaves. 'I'll try,' she replied. 'Come back in a couple of days.'

Jean Du Plessis makes many similar calls in Mto wa Mbu (Mosquito River) near Lake Manyara in his quest to provide some income for the local tribeswomen. 'It's difficult to believe, but there is a litter problem in the Serengeti,' he said. 'People go on game drives and just dump their cardboard and plastic picnic boxes. I'm trying to persuade the local women to make boxes from banana leaves that are biodegradable or that the tourists will want to take home. That way everybody wins: the environment and the people.'

Two days later we returned to the fruit seller and a perfect replica of the original had been turned out. 'It took me a whole day,' she said, 'but I think I will get faster. I could probably make about three a day.' That would represent about an extra £2 a day for her family; not much, but significant in a nation where the average wage is only £35 a month.

Du Plessis, a 26-year-old former ranger, wants Tanzanians to share in the prosperity that big game tourism is bringing to the country, but to do it in a way that does not harm the environment. Going on an African safari is hugely rewarding, he says, but looking at animals from inside a Land-Rover is a bit like sitting in a goldfish bowl; your feet literally never touch the ground, and after a few days you can feel strangely detached from the real Africa and its people.

Serena Active, Du Plessis's new arm of the Serena hotels and lodges group, aims to connect the safari-goer with the landscape and culture. He leads fascinating walks through Mto wa Mbu, describing the crops and meeting and talking to the locals who greet him with undisguised pleasure. These are not Disneyesque 'cultural experiences': no one tries to sell trinkets or entice you into their rudimentary shops; this is a real opportunity to learn about an almost medieval way of life.

We were welcomed by Bibi, an 80-year-old woman who showed us her home; an earth-floored, mud-walled, banana leaf-thatched hut, which she shared with her daughters and numerous grandchildren; children who would benefit directly from the walk we were taking that morning. Some of the profits from the £28-a-head charge go directly to the village. So far Jean has spent about £250 building a kindergarten out of local timber with a £350 concrete toilet block. Eighty children are taught in three sessions every day by a dedicated teacher part-funded by the walking project.

A few days later we sped down the Rift Valley escarpment on a 10-mile mountain bike ride that took us through the village again. Children ran out to greet us and stare at these strange creatures in helmets and backpacks. It was election day and the kindergarten, just like any school in Britain, had been turned into a polling station; a patient, humbling queue forming outside. We rode out to the Masai tribesmen's land on the banks of the lake where young children drove cattle herds 300-strong on to fresh pasture and maribou storks and brilliantly-coloured bee-eaters wheeled overhead in the warm air. The day before we had hiked for three hours with Du Plessis's partner, Megan Craft, amid the stunning scenery surrounding the Ngorongoro crater, a 100-square-mile caldera, formed nearly three million years ago.

We walked away from the crater and up the slopes of Mt Oldeani, passing cattle and goats kicking up clouds of red dust on their way down to drink. We encountered Masai tribesmen, visible for miles in their bright red tunics and armed only with spear and staff. This is a national park and home to all the wild animals of Africa; lion, cheetah, leopard, elephant, buffalo, rhino. While the area we walked was deemed to be away from their normal habitats, each hike is accompanied by an armed park ranger - just in case - but the fearless Masai put their trust in their mystic red and their spears.

We had spent the previous day and that morning in a Land-Rover, touring the crater, marvelling at the huge variety of wildlife, and were ready to stretch our legs. Leading the trek was Tim Mdinka, one of the seven staff employed by Serena Active who act as guides on walks and bike rides, bringing their local knowledge to bear when describing the dramatic landscape, the animals , the plants and the trees. Tim told us about life in Tanzania; how education is compulsory from seven to 14 , but how few go on after that; how families are still having eight to 10 children each; how the Masai honour their cattle (the larger the herd, the higher the status of the herdsman). He stooped down and picked some objects off the ground. 'Here, have these,' he said, handing them to my younger son Nicholas, 'they're zebra teeth.'

A little later he stooped again and picked up something bright; a carefully worked tool, like an arrow head. 'Something from a witchdoctor, I think,' he said and added it to Nicholas's collection.

Over the final ridge we watched the sun set over Lake Eyasi, a lovely sight made even lovelier by a glass of champagne supplied from a Land-Rover waiting to drive us back through the dark to the Ngorongoro Serena lodge. Far below us on the banks of the lake live the 500 members of the Hutza tribe - hunter-gatherers who wear animal skins and eat baboons. No government has yet been able to persuade them to send their children to school.

To help elect a new government, Tim joined us the next day for a lift back to Manyara. He had to vote in his home district, so chose to give up a day and a night to go to the polls; a country that has been independent for only 40 years values democracy rather higher than we do in this country.

We joined Jean again on our final day at Manyara for a hike down a river gorge to the gates of the national park. We were going to spend the whole day in the Land-Rover in the company of our excellent, knowledgable driver, Peter Njau, so it made sense to have a good walk beforehand - and some walk it was. We began by skirting along the edge of escarpment, followed by curious baboons. Jean explained that some 60 troupes live here, each with about 80 members. He pointed out mongoose, civet and bushbuck tracks; a hyenas den - 'don't stand in front of it. They rush out when disturbed'- and a termite mound, a teeming miniature city with 20 million inhabitants. 'They are rather tasty when fried. Like peanuts.'

After showing my sons how the damsel fly traps ants for her supper, Jean led us on a 400ft descent into a river gorge where great trees shaded the sun and water rushed over massive boulders. As we picked our way through the undergrowth, Jean told us of his background; he had worked as a ranger in the Kalahari and Zululand and managed game lodges across Tanzania. It was at Klein's Camp that he met Megan, who was conducting a year's research into the lions of the Serengeti. They both noticed that safari-goers needed to get some exercise after long hours in trucks and came up with their hiking and biking plans earlier this year. Abseiling and climbing followed and next year they plan to launch game-watching from canoes on Lake Manyara.

Mto wa Mbu, in common with a lot of Africa, has its fair share of street children, some abandoned by their parents, but more often orphaned by Aids. Serena Active want to employ about 15 boys to act as canoe crew, maintaining and launching the boats and manning the picnic stops. It's another example of the desire to get the local people positively involved in the benefits of tourism.

It seems a far cry from Jean's days as a game ranger. My sons listened spellbound as he recalled being charged by rhino and buffalo - and meeting lions face-to-face.

'It's the sound of their roars that really shakes you,' he said. 'It goes right through to your bones. But mostly it's a warning; they are not going to attack you, just give you a very, very big fright. You must stand completely still and they'll back off.'

We'll take your word for that, Jean...

Getting there

Serena Hotels has safari lodges and hotels in Kenya,Tanzania and Zanzibar (00 254 2 710511 or mktg@serena.co.ke).

Somak Holidays offer a Serena Serengeti Safari departing weekly from Gatwick for a six-night itinerary which includes one night at Lake Manyara Serena Lodge and two nights at the Ngorongoro Serena Lodge. Prices start from £1,213 per person. This includes return flights on British Airways transfers, game drives, full board and free regional add ons from 11 regional airports. 0208 423 3000 or email: holidays@somak.co.uk

Serena Active charge £28 for long hikes, village walks, biking and abseiling.