Purity Irungu and the other womenfolk of Kamangura village used to trek the 10km to Gathiuru forest in central Kenya each day to gather wood for cooking.
"I would need a load of firewood large enough to fill a pick-up truck every month," explained the 38-year-old mother of three. "But the firewood was not enough, so we would cut down trees."
Nowadays, thanks to an energy-saving cookstove, Irungu walks to the forest far less often to fetch wood. She is part of an innovative scheme, known as "Payments for Ecosystem Services" (PES), which rewards local people for protecting natural resources.
According to Tony Simons, director general of the Nairobi-based World Agroforestry Center (ICRAF), PES works in three main ways. Communities can be paid to stop activities that harm ecosystems, or they can be paid to do something new that supports ecosystems. The third option is for communities to co-invest in an activity that has good returns for the ecosystem, such as energy-efficient cookstoves.
"The activities must trigger transformation and make sense to the farmer, the village head or even the forest dweller," Simons said. "PES can either be in (the form of) cash, or by offering incentives and skills transfer."
A growing number of experts say PES could be a workable alternative to green schemes that aim to generate revenues by trading carbon credits. These have proved disappointing in many cases, not least because carbon prices have plunged in the past couple of years.
In Kamangura, non-profit group Nature Kenya and the Gathiuru Community Forest Association persuaded villagers to stop harvesting firewood from the forest in exchange for cheap cookstoves that use less fuel.
Association members were able to buy the stoves at a subsidised price of $1.70, far less than the market price of over $30, explained Harriet Gichuru, Gathiuru site manager for Nature Kenya. The money goes to purchase more cookstoves, which are made locally, for new members.
Under the deal, villagers are only permitted to collect firewood in specific places, to ensure forest conservation.
"Nowadays I use firewood collected from my farm because I don't need much," explained Irungu. "I use the lengthy hours I spent gathering firewood in the forest before to do chores like feeding domestic animals, fetching water and even doing casual jobs."
TREE LOSS THREATENS FOOD, BIRDS
Nature Kenya's Gichuru linked the encroachment of local people into Gathiuru forest with a decline in staple food production in Irungu's village.
Located on the flanks of the Mount Kenya Forest, the village has lost crops to erratic weather and spells of prolonged drought - a situation local elders blame largely on the loss of trees in Gathiuru.
Gichuru said the decline in forest cover was also threatening the Abbott's Starling bird, which is only found in the Mount Kenya Forest and parts of Tanzania, and now faces extinction.
The forest - also under the management of the Mount Kenya Biodiversity Conservation Group, a community-based organisation - is an important bird reserve that is home to some of the world's unique species, including the endangered Abbott's Starling.
"It likes to perch on high tree canopies," explained Gichuru. "But tall trees have disappeared because of illegal timber logging and forest encroachment."
Amid growing risks for the forest and its wildlife, Gichuru and other conservationists realised they must convince the inhabitants of villages like Kamangura to stop depleting forest resources.
This was not an easy task, because preventing rural communities from exploiting ecosystems can have a negative impact on their often fragile livelihoods.
So they decided to try the PES approach, hoping it might persuade Irungu and her peers to let the forest be.
More than 130 homes are now equipped with energy-saving cookstoves, and they seem to be having the desired effect.
"Cases of illegal encroachment into Gathiuru forest are now rarely reported," Gichuru said. "This proves that communities are willing to be involved in conservation if they are given alternative and workable livelihoods."
'PEOPLE STOP DOING THINGS WITHOUT PAY'
The Kenya Forestry Service (KFS) says similar PES schemes are being put into practice across the country's five "water towers" - forested mountain areas - thanks to climate change adaptation funding from donors and the national budget.
According to ICRAF head Simons, the real cost of releasing a tonne of carbon dioxide into the atmosphere is about $50 to $60, while it takes about 2,000 litres of water to produce a tonne of carbon. So if the carbon price is just several dollars a tonne, as it is now, that values water very cheaply too.
"Why should a small-scale farmer or a forest dweller or a sub-national jurisdiction manager maintain something that is good for everybody for such low prices? People stop doing things when you don't pay them," Simons said.
The forest service believes PES is possible in Kenya because most industries depend on the forest ecosystem in one way or another.
KFS assistant director Daniel Mbithi said water and forest conservation are among the sectors where Kenya is implementing PES. "Most of our agriculture depends on rainwater, but rain formation and rainfall are influenced by our forests," he said.
Meanwhile, opinions are divided over the future of carbon trading schemes in Kenya. In late January, the World Bank issued the first carbon credits from its Kenya Agricultural Carbon Project.
The first of its kind under a new carbon accounting system for sustainable farmland management, the project is expected to generate revenues of some $600,000 by 2017, though it is unclear how much of this will go to its 60,000 participating farmers.
Not all are convinced of the potential benefits. Three years ago, horticulturalist Gerald Gwatu learned at a chief's meeting that he could earn money from trees by joining community reforestation efforts. So he established a tree farm at his home in Mwati village in central Kenya.
"You can see the trees are big enough to harvest for firewood or charcoal," said the 38-year-old. "But I have not received a single payment from the carbon trading project. I would be better using my tree farm for other purposes that bring me money."
Supporters of "Payments for Ecosystem Services" say it could be a credible alternative to carbon-based finance, especially if carbon prices stay low.
"PES is the way to go because it engages the community on a day-to-day basis," said Joseph Ngondi of the Kenya Climate Working Group, an NGO. "Carbon trading is based on theory and so it cannot work for Africa."
Kagondu Njagi is an environmental writer based in Nairobi.