Amid the rocks, canyons and cactus of Arizona, an Englishman is laying down gardens. The object? To put an end to zoos. By Caspar Henderson
"There were storms to the south and masses of clouds that moved slowly along the horizon with their long dark tendrils trailing in the rain. That night they camped on a ledge of rock above the plains and watched the lightning all along the horizon provoke from the seamless dark the distant mountain ranges again and again".

The American south-west, described here by the novelist Cormac MacCarthy, captured popular imagination long ago. Its vast canyons and brilliantly coloured rocks feature in a thousand Westerns. And the saguaro, or "organ pipe" cactus, would come high on any list of the world's oddest-looking plants.

But, in a landscape that's almost a movie cliche, an iconoclast from the foggy shores of Britain is fomenting a revolution in public awareness and understanding of ecology. David Hancocks aims to do nothing less than drive the very idea of the zoological gardens into extinction - and replace it with something altogether new.

Hancocks is director of the Arizona-Sonora Desert Museum, which is in fact a zoo - or, as it now terms itself, a regional "biopark". Only a few acres in extent, the museum is second only to the Grand Canyon itself as the most popular visitor destination in the state of Arizona. Much of the natural history of the Sonoran Desert, which stretches from southern Arizona down into Mexico and is larger than Britain, is crammed into a tiny space perched on a mountainside. Its grounds afford a stunning view across untold miles of desert - rather as Hancocks's vision seeks to break the straitjacket of established thought.

"You have an 18th-century view driving what should be a 21st-century institution," he says, contending that zoos provide false comfort in the face of the most rapid extinction of species for about 65 million years. "Zoos have been saying for the last decade that their primary purpose is conservation, but I fear this is little more than a useful shield. They are saving species that are important to zoos, not necessarily to nature. In reality, they may well be doing a disservice to nature. We need to take a new, holistic view."

Hancocks never saw himself as a modern Noah. Studying architecture in London in the 1960s, he was appalled by the inhuman "machines for living" that characterised so much of British design at the time. Half-jokingly, his then girlfriend suggested that if he wanted to understand what kind of space people needed he should work with animals. Hancocks thought about it, and got a summer job at London Zoo. "The first day I started work I walked into a shed, one-third of the size of this office we're sitting in now. Nothing but bare concrete. It was the home of Guy the gorilla. He'd been sitting there, in solitary confinement, for 25 years." So, he says, "I came to work in zoos because I hated them".

In the 1980s, Hancocks was first architect and then director of the Seattle Zoo, in the rainy northwest of the US. Determined to create more than a series of "boxes for Linnean categories", he insisted on combining botanical with zoological exhibits, and (against all the most prestigious scientific advice) created habitats with abundant vegetation for the zoo's gorillas.

This spring he is overseeing the creation of the world's largest set of pollinator gardens, created to attract the vast range of animals that interact with plants in one of nature's most intricate and extraordinary dances. An already extensive butterfly garden, with scores of attractant flowers, is being moved and expanded. Another garden is being planted with species including Datura and Oenothera, which flourish in the desert and whose flowers open at night, to encourage the large and astonishingly agile hawk moths. Other areas will feature yucca plants and yucca moths, on which they depend, and a display of agaves pollinated by migratory bats passing through the Sonoran. And in the summer, the existing cactus and succulent garden will also get a native bee garden and "nesting ramada", offering plentiful burrows and holes, which bees like.

"Pollination", explains Hancocks, is "one of the simplest stories of interconnectedness." The new gardens are to be a living testimony to a "Forgotten Pollinators" campaign, co-ordinated from the Desert Museum.

The campaign is a call to arms and national policy in the face of what Gary Nabhan, the museum's director of science, calls an impending ecological crisis. He explains that human-induced changes in populations of pollinators, which include bees, butterflies, moths and bats, threaten a ripple effect on disparate species, ultimately leading to a "cascade of linked extinctions".

The causes are overuse of chemical pesticides, unbridled development, and conversion of natural areas into cropland where a single crop is planted - that is, monocultured. Already, he says, "the once-abundant honey bee is suffering dramatic population declines throughout North America". The ramifications for farming are potentially grave: crops such as tomatoes and alfalfa, a basic livestock feed, depend on pollination.

It has been more than 30 years since Rachel Carson predicted a "silent spring", devoid of the chorus of insect-feeding birds, one where "no bees droned among the blossoms". Carson, who was writing about animal deaths caused by the build-up of DDT, also suggested that fruitless autumns would become more commonplace. Perhaps more than any other warning in the past 50 years, it changed the way farmers, wildlife managers and policy-makers perceived environmental protection. But, of all her commentaries, the one that has been least heeded or understood was her warning that habitats are being fragmented by physical destruction and chemical disruption.

"We are only beginning to understand even the most obvious relationships between flowers and their pollinators," says Stephen Buchmann, a research entomologist at the Carl Haden Bee Research Center and adjunct professor at the University of Arizona, who co-ordinates the Forgotten Pollinators campaign with Nabhan. The Sonoran Desert offers the ideal natural laboratory. "It is the most bee-rich piece of real estate in the world," says Buchmann. Some 1,500 bee species - from the giant carpenter bee to tiny leafcutter and sweat bees - thrive on about half as many kinds of native plants.

That diversity flies in the face of an ecological truism, that the farther you travel from tropical zones, the fewer species of animals and plants you encounter. Yet bees are nowhere so abundant as in savannahs and deserts, and no desert is as hospitable to them as the Sonoran.

Looking back, Hancocks says: "Britain probably has more zoos than anywhere else in the world. It's a wonderful legacy, but it's time to move on. Very few of them do much work of true scientific or educational value. Both Britain and the rest of the US should ditch the old zoo model, and create regional `bioparks' and study centres like the one we're building here"n