Vanishing forests have brought flash floods, erosion and mass displacement of wildlife.
This year alone Zimbabwe has earned a record $777 million dollars from tobacco sales mainly to China.
Some 20,000 new tobacco growers have entered the market in the last year - raising production to 250 million kg.
Tobacco has been credited with reviving the rural economy in a de-industrialising country 80% unemployment.
And according to the country's lobby The Tobacco Industry Marketing Board, 32% of growers this year in Zimbabwe are women.
Flue-cured tobacco (also called Virginia tobacco) is Zimbabwe's most lucrative cash crop dwarfing maize, cotton or flowers. Tobacco sales provide 26% of the country's foreign currency earnings. But tobacco has been an outright doom for the country's natural woodlands.
Zimbabwe along with Tanzania and Malawi produce 75% of all tobacco in Africa. Their high quality tobacco attracts cash rich buyers from China, Dubai, Belgium, Japan and South Africa. And Zimbabwe is now the third greatest producer in the world after Brazil and the USA
A deforestation crisis
This story of economic progress is however is a catastrophic environmental disaster for the African country - 15 % of its natural forest has been burnt down as farmers free more land to plant tobacco. On current trends, the country will be a desert in just 35 years from now.
For a grim start, small scale farmers who make up 80% of the country's 87,000 tobacco growers are clearing 5.3 million trees as they expand tobacco plots and triple their profits.
"The national rate of deforestation currently stands at more than 300,000 hectares per annum of which 15% is attributable to tobacco production activities", moans Zimbabwe's watchdog The Forest Commission Agency.
According to the agency, this horror means that Zimbabwe is losing woodlands which are three times bigger than its sprawling capital city, Harare, every year.
Flue-cured tobacco is highly energy-intensive, requiring intense heat to dry out moisture from the crop's leaves. Curing means circulating hot air around the crop for seven days.
This means direct disaster for natural forests as farmers lay their hands on previously protected prime forests. Water bodies are also infected and dried by pesticides as farmers protect their crop from diseases.
Zimbabwe's annual rate of deforestation has risen sharply from the 1.5% recorded in 1997, according to the United Nations Development Programme - and now stands over 20% higher. In the same period the number of tobacco farmers increased from 1,400 to 87,000.
The United Nations Environmental Protection Agency claims that "fuel wood scarcity, land degradation and deforestation in developing countries can be linked to tobacco farming."
Coal or wood?
The heat could be provided by coal, but so long as wood is available cheaply, or even free, for the trouble of cutting it down, it dominates the country's production.
Vanishing forests have brought flash floods, erosion and mass displacement of wildlife.
Small scale farmers who seized swathes of plots from displaced white Zimbabwe farmers in 2000 do not have sufficient money and will to buy coal and dry their tobacco. Coal in Zimbabwe costs a prohibitive $250 per tonne.
Moreover coal fired drying barns need electricity to circulate the heat - and Zimbabwe is chronically short of power. So firewood is the easy, but hazardous, alternative to coal.
Each small scale tobacco farmer in Zimbabwe owns 3.2 hectares of cropped land according to The African Consultancy Intelligence. A smallholder typically grows 1,400 kg of tobacco per hectare, which needs seven tonnes of firewood to cure.
To prepare tobacco for sale nearby forests are cleared and the wood stockpiled to heat and dry the crop. For example, in 2011 around 635,000 tonnes of firewood were used to cure 127 million kilograms of tobacco. According to the United Nations Environmental Protection Agency, this translates to 46,000 hectares of lost forest.
Flash floods and erosion
In Mashonaland province, commonly referred to as the 'Tobacco Belt', deforestation has laid land bare and arid, bringing flash floods, erosion and mass displacement of wildlife.
Here farmers are draining wetlands and drying shallow wells as they extend their fields. In just two years time the province will have no forest left, fears the Consultancy African Intelligence.
Fuelled by China which bought 328 million kilograms of tobacco in 2014, the price of tobacco in Zimbabwe has shot up as high as $6 per kilogram, though prices have since fallen back.
To worsen matters, Zimbabwe farmers prefer tobacco to food crops like bananas, wheat or maize, which has to be sold to the government buying agency at a low fixed price. The agency can also leave farmers waiting for two years for payment.
This leaves the country on the edges of acute hunger as self-sufficiency in food is undermined.
Cut less, grow more!
Small scale farmers are not disturbed by tobacco's severe impact on the environment. The judicial fine for destroying forests in Zimbabwe is too low. Offenders only have to pay $300 no matter how large a forest burnt down.
The country's laws compel flue-cured tobacco farmers to establish fast growing tree species as replacements. "Forests have a paramount contribution to make as engines of future sustainable development", says Mr. Saviour Kasikuwere, Zimbabwe's water and climate minister.
In 2011 the country's largest replanting target was met with 10 million new trees. However there is a doubt how many of the new trees survived due to the wild fires that often accompany tobacco farming.
Farmers are also encouraged to grow fast-growing eucalyptus on their own land to provide the wood. But many are reluctant as this would mean giving up land for tobacco cultivation, while the trees are also highly water demanding.
Rocket barns
In an attempt to tackle the problem British American Tobacco has introduced what it called a 'rocket barn' - a tobacco drying kitchen that uses uses 50% less firewood by burning only wood harvested from commercial forests not natural ones.
'Rocket barns' are more fuel-efficient than traditional drying barns, and work by using emerging exhaust smoke to draw in dry air. They are insulated with 50 millimeters of grass thatch. Its wide chimney not only removes smoke from the furnace but also expells moisture from the barn.
Where conventional tobacco barns use 530 kg of wood to cure 5 bales of tobacco, a rocket barn uses 290 kg of firewood to cure the same quantity according to Zimbabwe's Tobacco Research Board (TRB).
Dahlia Garwe, TRB chief executive, says rocket barns are designed to promote high combustion efficiency minimising the release of ozone pollutants to the air, while "quality of cured leaf is improved in rocket barns. Excessive heat from metal pipes in old barns damages the crop's leaves."
They also use small branches and twigs, she adds, "thus making it possible for the farmers to use branches for curing instead of cutting down the while tree."
The TRB has distributed 10 000 rocket barns to small scale farmers from 2013 at agricultural shows, field days and auctions. Statistics show that 60% of farmers who received bans adopted them.
But other farmers complain of the cost of rocket barns. They cost $800 to $1,200 with labour and building - ruling it out as an option for under-capitalised farmers including most newly established tobacco growers.
Also with the widely fluctuating tobcacco price, farmers feel insecure making long term investments, even if they have retained the money needed from past profits.
Change, or disaster will follow
Tobacco stands as an unhealthy balancing act for Zimbabwe. It is earning vital dollars in the short term, and bringing welcome prosperity to almost 100,000 farmers including women who have benefitted from the country's land redistribution programme.
But the sector must urgently move to more sustainable pratices, or the long term cost will surely prove disastrous for the country and its people not least its farmers.
Ray Mwareya is based in Zimbabwe, where he edits The Africa Scientist magazine.
