Tom Lodge: This spiralling crisis in Zimbabwe threatens the future of Africa

Migration and electoral aspirations will cease to act as safety valves and urban anger will explode

The clashes between land invaders and white farmers in Chinhoyi last week represented a new threshold for communal conflict in Zimbabwe. Twenty-three farmers are now awaiting trial in prison after having being denied bail in the wake of skirmishes with Zanu-PF "war veterans". For the second time in two months, farmers had assembled a "reaction stick" to protect themselves. Both sides in the conflict employ the bitter lexicon of the Chimurenga War, evoking passions which as each day passes seem less and less susceptible to external diplomacy.

Neither the latest joint initiative by Commonwealth foreign ministers nor the threat of American sanctions are likely to deflect Robert Mugabe from the course he has taken to ensure himself victory in next year's Zimbabwean presidential elections. His own country's history is instructive: Ian Smith's Rhodesia survived 16 years of international ostracism and a decade of guerrilla war before he abdicated authority. By 1978, with half its farms affected by the insurgency and with most of its managerial workforce in uniform, Rhodesia was probably closer to the "meltdown" that the International Monetary Fund predicts for present-day Zimbabwe.

Of all the sources of pressure that brought about eventual Rhodesian capitulation, South African threats to withdraw economic support were certainly the most compelling. But Robert Mugabe has yet to experience anything resembling a threat from his soft-spoken neighbour, the President of South Africa. Although Thabo Mbeki laconically conceded in a BBC interview that Mr Mugabe wasn't listening to any advice from Pretoria, his spokesmen later insisted that South Africa was not contemplating any change in its policy of political dialogue and economic engagement

Two considerations explain the South Africans' reluctance to use the economic leverage they possess as Zimbabwe's main supplier of food, power and fuel. The public reason offered by foreign affairs spokesmen is that South African threats or sanctions would precipitate total economic collapse and a huge intensification of political conflict, events which would harm the region as a whole. As the situation in Zimbabwe deteriorates, this first rationale for restraint is probably becoming less compelling. Even so, Mr Mbeki will still be reluctant to adopt any course which will set him apart from pan-African opinion, particularly at a time when South Africa depends on consensus among African statesmen for its leadership role.

For the time being, therefore, Mr Mbeki will be glad to use the Commonwealth initiative as an alibi for inaction. Sooner or later, though, events will compel the South Africans to take a tougher line. "Meltdown" might be an overstatement but, with nearly a year to go to the presidential elections, pinning hopes on a democratic resolution to the crisis or a Zanu-PF palace-coup seems unrealistic. Neither are likely without external inducement. Too much harm may be done in the interval. In any case, if Robert Mugabe declares a state of emergency as he has threatened to, in response to US sanctions legislation, then the election won't happen until he has used martial law to destroy any organised opposition.

The consequences for the region will be catastrophic; lacking the capital resources for its own regeneration, it depends on foreign business confidence. If southern African leaders are prepared to tolerate total democratic breakdown in Zimbabwe, they can give up any prospect of fresh investment.

Already, Zimbabwe's economic plight is beginning to threaten the region's food security. Ten year's ago Zimbabwe was a net food exporter. Today it must import 800,000 tons of cereals to feed its population; this year's harvest will be down by 25 per cent from last year's. Tobacco exports are in sharp decline as well, making it harder for the country to pay for the food it will need to buy abroad.

Well managed land reform can increase productivity, but Zimbabwe's "fast track resettlement" of 2,500 farms has merely resulted in commercially productive land being transformed into squatter encampments incapable of feeding the cities which accommodate about a third of the population. Some 340,000 farm workers will lose their jobs if the government implements its threat to expropriate another 5,000 farms.

In the cities, 400 industrial companies closed doors in the past twelve months; unemployment, now at 40 per cent, is unprecedented. In July, a 70 per cent fuel price rise prompted a two-day general strike.

Protest has been relatively orderly so far; most commentators agree that violent political activism is still largely state sponsored and, moreover, located in the countryside. Zimbabwe's city dwellers have yet to witness on a large scale the food riots which analysts have been forecasting, though during the fuel strike bread delivery trucks were overturned and set alight.

Sooner or later, though, cross border migration and electoral aspirations will cease to act as safety valves and urban anger will explode. If that happens, the loyalty of Zimbabwe's already demoralised army will be put to its severest test. Helping peasants move house to white farmland may not be what soldiers expected when they joined up but it probably didn't cause them any moral anguish. Enforcing martial law against their kinsfolk in the townships will be a different matter.

Militarised political conflict in Zimbabwe – a real prospect when the government starts using soldiers to suppress civilian protest – is a threat which the region cannot ignore. Unofficial immigration across the Limpopo to South Africa is now running at about 100,000 a year.

Mr Mbeki is unlikely to issue public ultimatums, but Harare will soon learn that in a state of emergency, petrol, electricity and grain will require cash up front at commercial prices – and that deliveries may be subject to delays. The 200 holes in the border fence will be mended and there will be no more shopping visas issued to Zimbabweans at Beit bridge. South Africa will halt its negotiations to buy Zimbabwe's bankrupt state businesses. Discreet economic bullying might just be enough. Mr Mbeki must know this just as he knows that another year of Robert Mugabe will turn his African Renaissance into just another pipedream.

The writer is Professor of Political Studies at the University of the Witwatersrand, South Africa.