Kenya is planning to erect thousands of miles of electric fencing around its key national parks and to double the number of armed guards to protect water sources and stop impoverished people felling trees, as the effects of climate change become more serious.

A drought that has left more than five million people without food this year, combined with changing weather patterns and rapid population growth, threatens a triple catastrophe within 10 years, according to Julius Kipng'etich, director of the Kenya Wildlife Service, the government's paramilitary organisation responsible for managing 26 national parks and their wildlife.

"The long rains have failed for the first time. The implications for food security and water scarcity and energy are profound. Kenya will face these three crises in the next 10 years without a doubt. If we carry on the way we are going, in 20 years the consequences will be horrific", Kipng'etich told the Observer.

Five of Kenya's national parks provide drinking water and hydroelectric power for almost 80% of the country as well as being major centres of wildlife. But several have been invaded by squatters after the former president, Daniel arap Moi, gave politicians land in forested parks in the 1980s.

The 15,000 people who now live illegally in the heavily forested 400,000 hectares (999,600 acres) of Mau park in the west of Kenya have cut down nearly 104,000 hectares of trees in 15 years. The government has pledged to evict them, but has so far failed to take action. Other parks have been invaded by people taking cattle to graze or by charcoal industries.

The Mau is the largest forest in Kenya, and is considered critical for safeguarding water supplies there as well as in neighbouring Sudan and Uganda. Millions of people depend upon the 12 rivers that flow from the mountainous area, and which provide water for the tea, livestock and energy industries. Other forested parks provide water for the capital, Nairobi, and hydroelectric power stations. Trees are an essential part of the water cycle as they promote the formation of clouds – cutting them down inevitably leads to lower rainfall.

Last week the wildlife service said it planned to double the number of armed guards in Kenyan parks over the next five years and was studying whether to put electric fences around Mount Kenya, the Mau forest, Mount Elgon and the Cherangani hills. The model would be a 250-mile fence which has almost been completed around the Aberdare mountain range by the Kenya-based conservation group Rhino Ark.

"Kenya is destroying itself. The population has reached an unsustainable level. We are killing ourselves slowly by destroying the forests and settling there. Destruction of the Mau is like dancing with death. We should see environmental destruction as a greater threat than anything else," said Kipng'etich.

Environmentalists foresee a vicious circle where human and wildlife conflicts will escalate with climate change as east African rains fail and people are forced to enter protected areas in search of food for animals and water. Destruction of the forests will devastate wildlife and further reduce water supplies to Kenya's cities.

"Once you have people in the forest, you cannot control what they do. Kenya depends on these forests. You cannot solve the problems of food and water by allowing poor people to go into the forest. People are undermining the future of Kenya by growing food in the forest," said the Kenyan environmentalist and winner of the Nobel peace prize, Wangari Maathai.

Britons fund nearly 50% of the wildlife service through park entry fees paid by 300,000 visitors a year. Britain will now be asked to contribute to a €100m (£90m) European commission fund to help Kenya adapt to climate change. The income from the fund is intended to be used to help communities prepare for expected water shortages and extremes of weather.