Massive geopolitical shifts seldom announce themselves with a bang. They tend instead to creep up slowly, until it's hard to be sure exactly when they began. I remember going to buy some steel about six years ago, and being staggered by the price. "Ah," the man in the hardware store explained, "it's the Chinese, you see. They're buying up so much steel, the price has gone through the roof." The last time I visited my brother, all the lead had been stripped from his garden shed – the second theft in two months – thanks to rocketing lead prices. And it must have been around the time of the Iraq war that I recall first hearing someone say the next big war would be fought over water. At the time the prediction had sounded far-fetched; these days, it's a commonplace.

These sort of random, disconnected events look neither random nor disconnected once you read Dambisa Moyo's account of what's happening to the world's commodities. In 1950 the world's population stood at 2.5 billion; by last year it had reached 7 billion, and is projected to hit 10 billion by 2050. With almost all the population growth occurring in the emerging economies, by 2030 some 2 billion people will have joined the global middle classes. "Put another way," Moyo writes, "in less than 20 years we will witness the creation of a middle class of roughly the same size as the current total population of Africa, North America and Europe." Naturally, they will want mobile phones, fridges, cars and washing machines; 2,000 new cars already join Beijing's streets every day. In 2010 China had 40 cities with populations of more than a million; by 2020 it plans to have added another 225. The implications for the world's commodity resources are stark and sobering: global demand for food and water is expected to increase by 50% and 30% respectively by 2030, the pressure on copper, lead, zinc and corn is already becoming unsustainable, and no one has a clue where the energy we'll need is going to come from.

If Moyo's calculations are correct, we are in big trouble – which makes the central premise of her book, Winner Takes All, all the more arresting. Governments across the world, she writes, have singularly failed to grasp what's coming – with one sensational exception. "Simply put, the Chinese are on a global shopping spree." State-sponsored Chinese corporations are busy buying up commodities across Africa, North America, the Middle East, South America – anywhere they can – in a concerted strategy to seize control of resources before the rest of the world wakes up to the looming crisis. They're striking deals with what she calls the "axis of the unloved" – developing countries rich in commodities but poor in political and economic capital – in return for much needed investment, employment and infrastructure. Extravagant shoppers, the Chinese are happy to pay over the odds, treating their trading partners not as poverty-ridden charity cases nor political pariahs but valued commercial equals. But when the resources begin to run dry, the consequences will be catastrophic. Already, since 1990 at least 18 violent conflicts worldwide have been triggered by competition for resources. If nothing is done now, warns Moyo, commodity wars on a terrifying scale are all but inevitable.

To western eyes, Winner Take All makes for scary reading. Viewed through Chinese eyes, on the other hand, it's an altogether different story. For all its premonitions of armageddon, the book's tone feels more congratulatory than cautionary – reflecting the particular perspective of its author.

Moyo stepped off a transatlantic flight only hours before we meet, but arrives looking like a supermodel, shrugging off jet lag with the indifference of someone who, when asked where she lives, replies: "Oh, on a plane." Born in Zambia in 1969, she spent her first eight years in the US before returning with her parents, both economists, to the capital, Lusaka. At 19 she left again for good, acquiring a masters from Harvard and a doctorate from Oxford, and working for the World Bank and Goldman Sachs, before publishing her first book, Dead Aid, in 2009.

A turbocharged attack on aid, it caused quite a sensation – here was an African denouncing western aid as patronising and counterproductive – earning Moyo the nickname "the anti-Bono" and securing her reputation as a box-office star of the global high-finance circuit. Her second book, How The West Was Lost, was a devastating obituary of America's supremacy, the cause of death diagnosed as a fatal overdose of greed and laziness. With blue-chip western academic credentials, yet a distinctly non-western way of looking at the world, she was named one of the world's 100 most influential people by Time magazine. Yet her latest work, she says, was inspired by her own ignorance.

"I'm pretty savvy; I kind of understand what's going on in the world. So I was quite surprised to learn how little I knew about commodity scarcity. I was very shocked by my own ignorance. It just seemed to me surprising that the only country that seemed to be doing something in a very systematic and deliberate way was China."

Winner Take All is presented as a warning to the west – it's subtitled China's Race For Resources, and What It Means For Us – but the book reads more like a hymn of praise to China. When I ask if she regards its story as scary or thrilling, she doesn't hesitate. "Oh, I think it's fantastic. I think it's fundamentally fantastic – and also in the literal sense of the word. You know, it's fantastic – it's a good thing – but also 'fantastic' as in something really tremendous. They bought a mountain in Peru – half the height of Mount Everest – they bought the mineral rights. I flew in from Canada this morning, where they've done a laptops-for-pork deal. They're importing beef from Brazil, and in return they'll build roads and railways. It's just an amazing display of discipline, and a systematic approach – it's unparalleled. I don't know any other country that does it in this way."

If anything, the chief inspiration for Winner Take All seems to have been Moyo's irritation with western attitudes to Chinese growth. "There is this obsession with China being a culprit," she agrees. "Even now, people will still say: 'Oh, the reason why the United States' economy is not doing well is because the Chinese are manipulating the exchange rate,' or, 'The Chinese have human-rights issues,' and, 'The Chinese don't do democracy, and the Chinese cheat.' You know, it's always about the Chinese, and no one actually takes a step back and thinks: 'Gosh, actually, it's our fault that productivity is declining. It's got nothing to do with the Chinese.'"

The hypocrisy of western criticism is, she says, quite breathtaking. We accuse the Chinese government of meddling in free-market capitalism, clean forgetting that US farm subsidy programmes and Europe's Common Agricultural Policy have condemned Africa's farmers to poverty. The US is perfectly happy to take China's money – more than $1tn worth of government bonds – yet expects the emerging markets to say: "No, we don't want Chinese money because there's an issue of human rights." We complain that the Chinese are paying too much for commodities, instead of wondering whether China might in fact have grasped their true value. And we have the nerve, she marvels, to accuse China of neocolonialism, failing to understand that "the rest of the world actually thinks what China is doing is pretty damn clever". It was the west which got rich by invading and plundering the rest of the world, whereas China is engaging with it on respectful, peaceful, generous terms.

"What the Chinese are trying to do – move a billion people out of poverty – is just an unheard-of thing in history. The fact that they have moved 300 million in 30 years is unheard of. It took Britain 156 years to double its per capita income. It took America 57 years, Germany 65 years. It's taken the Chinese 12-and-a-half years."

Moyo stresses more than once: "I'm an economist, not a political scientist," and her writing is full of the maddeningly opaque jargon of commodity trading. Yet the book's fundamental message seems to be as much about the contrasting politics of Washington and Beijing as commodity prices. She is always described as a passionate free-market capitalist, so I ask how that fits with her admiration of China.

"I have to tell you, this is my favourite thing about being raised in Africa; we don't do labels very well, we don't do this, 'Oh, you're a Democrat; oh, you're a Republican.' Because we live in the real world. There's not a single country that actually approaches economics in a pure, free market, capitalist way. I like the free market – but it very much exists only in textbooks. If I had a choice, and we could live in a very pure world, I would be a supporter of the free markets. But because we don't live in that world, I do really admire what the Chinese have done. Having the good fortune of being born in Africa – I absolutely love the fact that I was raised and born in Africa – I love people who deliver results."

Moyo's critics say her predictions of a commodity crisis are alarmist, failing to account for future technological solutions to shortages. People have been worrying about unsustainable population growth ever since Thomas Malthus in 1798, goes this critique, and yet the world always somehow manages to muddle through.

"Right, but the people who are saying: 'We'll muddle through,' are people sitting in the west who get clean water when they turn the tap on. If you're in India, and the Brahmaputra river is being rerouted by the Chinese, you're not muddling through; lives are being lost. Wars are being fought right now. 'Oh, we'll muddle through,' is a very western view, because you're not killing each other yet, and oil prices haven't risen to $1,000 a barrel. If you live in a poor country, where you have to walk miles for water, or you have to fight for water or resources, it is already happening." She invests her money in technology and innovation, she adds. "And my sense is that we're not close to any big discovery in any of the categories – land, water, energy and minerals – that has made me not nervous about the coming headwinds."

Other critics dismiss her predictions of scarcity as miscalculations based upon a flawed assumption that China and other emerging markets will continue to grow at their recent prodigious rate – when in fact, their economies are starting to slow, and have probably already peaked. "People do not understand," she says, with a hint of weary incredulity, "that the Chinese government will and can do pretty much anything to make sure they don't have a recession. They're not going to sit there and do nothing while an economy slows down to 5% growth a year. They will have a political problem; they will have Tiananmen Square, they will have people on the streets. So what do they do? They'll turn the taps on." The notion that African aspirations could now be switched off strikes Moyo as equally laughable. "I go to Africa all the time. You talk to a young person and tell them they can't have Facebook? Seriously? You try telling them that."

It's not hard to see why Moyo is such a hit as a public intellectual. But when we come to the logical conclusion of her thesis, her position seems to become somewhat illogical. She calls for the creation of a global body focused exclusively on commodity issues – but when I ask what it would look like, her only clear stipulation is a central role within it for China. If China is winning the commodity race, its interest in any such body strikes me as doubtful, but Moyo thinks self-interest will ensure their support for a strategy to prevent resource depletion and consequent conflict. "I think the world will be drawn into a war for resources," she says firmly. "I think we'll see more wars."

Yet if all her predictions are correct, at that point surely the Chinese will flex their considerable military might in order to protect the worldwide interests they've paid for. It would be perverse of them not to, wouldn't it? Moyo flatly refuses to see it.

"They have been very deliberate in their speeches that this is about the peaceful rise of China. And by the way, what kind of campaign would they launch? They would go to all those countries and be fighting in all those different countries at the same time? I don't know how they would be able to do it. I can't play that scenario out." Perhaps my scepticism is simply evidence of the sort of suspicious western mindset Moyo scorns, but I wonder if her determination to champion China might not be in danger of tipping over into blind faith.

Moyo is clearly well aware that her critics dismiss her as more of a showy controversialist than a sober-minded thinker. When I ask about the factual errors that have been seized upon in all three books – in Winner Take All, for example, she says Opec stands for Oil Producing Exporting Countries – she bristles defensively. "Well, I wish I had been more perfect. But my book hit the New York Times bestseller list last week, and people seem interested in what I have to say." She considers it "rather cheap" to indict a book because of a few inaccuracies, and suspects critics make so much of her mistakes because they cannot forgive the heresy of Dead Aid. "They think I'm speaking out of my place." As for "the anti-Bono" nickname, "I absolutely despise it. When people make those type of cheap headlines, it takes away from fundamental points."

There certainly seems to be more than a hint of subtle prejudice in some of the comments she has attracted – both positive and negative. Nigel Lawson called her "confused" and "muddled" in a BBC radio debate, while his son Dominic has praised her as "a very serious lady indeed", and I can't imagine him describing a white male equivalent as a "very serious gentleman indeed".

She has homes in New York and London, but is anxious to point out: "That sounds all very glamorous, but it's just where I throw my stuff," and insists: "My core, core, core: I'm an African." I ask to what extent she suspects her work is viewed through the prism of her identity as an African woman. "Woman? Zero. African? 100." Given her own emphasis on the influence of African origins on her work, I can't work out if she considers this unfair or not.

"I think," she reflects with an elegant shrug, "I'm kind of a hard bird to figure out."