VARGINHA, Brazil A freak tornado and floods last month may be a harbinger of a troubled future for Brazilian farmers, who worry that climate change could severely disrupt production in one of the world's breadbaskets.
Rising temperatures, a shift in seasons, and extreme weather in coming decades are likely to cut output in some areas and wipe out crops entirely in others, experts say.
"Brazil is vulnerable. If we don't do anything, food production is at risk," says Eduardo Assad, an agronomist at the government's agriculture research institute, Embrapa.
At stake is a $250 billion farm industry, food for millions of poor and supplies to world markets of Brazil's major export crops such as soybeans and coffee.
Brazil is seeking a leadership role in global climate talks and says it will adopt targets on greenhouse gas emissions, after agreeing last year to slash Amazon deforestation in half. But it has been slow to research climate change, its impact and how Brazilian agriculture can adapt to the changes.
In the poor northeast region, sparse rains will diminish further and temperatures will rise by 3-4 degrees Celsius (5.4-7.2 degrees Fahrenheit) by 2050, compared to a 2 degree Celsius national and global average rise, according to Brazil's National Institute for Space Studies (INPE).
Higher temperatures threaten to wipe out staple foods, such as cassava, for millions of people in the region.
"The northeast will lose one-third of its economy if we do nothing," Environment Minister Carlos Minc told Reuters.
Big export crops are also likely to suffer, according to a study by Assad and Hilton Silveira Pinto, an agronomist at the University of Campinas in Sao Paulo state.
The report, completed in May, says by 2020 soy output will fall by 20 percent and coffee by 10 percent.
Brazil is the leading exporter of coffee, beef, soybeans, orange juice, and other farm products. Only one cash crop stands to gain: warmer temperatures will double the area suitable for sugar cane as early as 2020, Pinto and Assad say.
SIGNS OF CLIMATE CHANGE
There are signs their predictions may be coming true, with last month's unusual tornado becoming the latest example of bad weather to destroy crops and houses in the country's south.
"We're seeing the beginning of climate change. The frequency and intensity of rains changed measurably and will continue to do so," says Jose Marengo, an INPE climate expert.
In Varginha, in central Minas Gerais state, Ivo Bueno Paiva points to his infested and depleted coffee trees. In five of the past 10 years, rainfall was well below the historic average, shriveling leaves and drying out flower buds.
Thousands of small coffee farmers, already struggling with rising costs and low prices, lost money and racked up debt.
"The more the rains change, the more my debt rises," says 76-year old Paiva, who was dressed in soiled trousers and a tattered shirt.
This hilly region accounts for half Brazil's coffee but by the second half of the century may produce no more. "The chances for coffee to survive in southeastern Brazil are slim," the Assad-Pinto study says.
Even slight changes in temperature or precipitation can be devastating for the flowering, growth and harvest of crops.
Excessive spring rains in Brazil's temperate south in recent years have damaged barley and wheat, part of which was processed into animal fodder instead of malt for beer.
As a result, the Cotrijal cooperative in southern Rio Grande do Sul state lost around 1.5 million reais ($830,000) in 2008 and disease from dampness is also damaging wheat production this year. Cotrijal has set up weather stations and asked agronomists at the state university for guidance.
"We can't change our planting calendar or the rains. How can I minimize my risks? We hope science will provide some answers," says Gelson Lima, production director at Cotrijal.
Rising temperatures could eventually cause wheat and barley to be entirely displaced, forcing up imports.
"We may have to replace wheat with cow pastures or tree plantations," says Jose Mauricio, head of wheat research at Embrapa in Rio Grande do Sul.
Technology can help farmers partially adapt to climate change, but results from experiments have been mixed.
At an experimental farm in Varginha, researchers seeking to mitigate droughts plant coffee trees in forests, where it is cooler and more moist. But less light reduces output and the inability to use machines increases labor costs, tests show.
Irrigation is expensive and water sources are scarce.
Government scientist Carlos Henrique Carvalho is working on more heat-resistant coffee varieties with longer roots. But developing new varieties takes over a decade, he says.
Seed company Monsanto will launch drought-resistant corn and soy by 2014 in the U.S. market but only five years later in Brazil. Even these will be only a partial fix.
"They can minimize the impact but won't solve the problem," says Rodrigo Santos, head of strategies and product management at the Brazilian subsidiary of Monsanto.
Even genetically modified plants will have difficulty adapting to temperature increases beyond 2 degrees Celsius, says Assad. Other scientists are more optimistic.
"I'm confident that science can provide 90 percent of the answers to climate change," said Edson Silva, director at the Parana state research company Epagri, which has exported a drought-resistant apple variety to France, Germany and elsewhere.
But research in most farm sectors has only just begun and spending is inadequate. Farmers need capital to migrate crops as well as proper infrastructure for processing and transport.
Developing a new crop costs 12 million reais ($6.7 million) per year over a decade and Brazil spends only a fraction of what it should, says Assad.
"Brazil was slow to believe in climate change, now we need to catch up by spending more -- much more," he says.
(Editing by Stuart Grudgings and Chris Wilson)