NAIROBI (Reuters) - Kenya said on Wednesday it would plant 7.6 billion trees over the next 20 years to redress decades of chopping down forest cover, the effect of which is now being felt in acute water and power shortages.

Just 3 percent of land in the agriculture-based east African economy is covered by forests that are protected by the authorities, compared with a government target of 10 percent.

“We will have to plant 4.1 million hectares in order to make a percentage that is internationally acceptable,” Environment Minister John Michuki told reporters.

“You are talking about 7.6 billion trees,” he said. “In my estimation, it is going to cost us $20 billion over 20 years.”

That amount is nearly twice the government’s annual spending, which will be about $11 billion in fiscal 2009/10.

By comparison, the authorities in Nairobi expect to spend just over $650 million this year on the country’s crumbling roads, and around $400 million on energy projects.

The impact of forest destruction is being felt by Kenyans, with rivers drying up and hydro-electric power generation, farm production and tourism all suffering as a result.

Kenya’s biggest forest, the Mau, has lost a quarter of its 400,000 hectares in recent years to unchecked human settlement, illegal logging and the burning of charcoal.

A report released by Prime Minister Raila Odinga last month showed that politicians had been allocated large parcels of Mau land by corrupt officials, mostly during the 1990s.

Michuki was speaking at the launch of a solar-charged mobile phone handset costing just 2,999 shilling ($39) by Safaricom, the nation’s leading mobile operator.

There are some 18 million active SIM cards in Kenya. But only about 18 percent of its 36 million people have electricity in their homes. Mobile users in rural areas not linked to the national grid often have problems charging their phones.

(Reporting by Helen Nyambura-Mwaura; Editing by Daniel Wallis)