As climate change takes a toll on yields across the country, scientists are encouraging farmers to grow eucalyptus tree due to its unrivaled ability to weather changes in climate with findings showing a one-hectare piece of land which has 840 eucalyptus saligna trees being capable of sequestered 337 tonnes of carbon over eight years.
Farmers who have traditionally relied on the tree for commercial purposes like timber, charcoal making and other uses are now being encouraged to expand area under cultivation as scientists discover the tree’s unrivaled ability to weather changes in climate. A study by Kenya Forest Research Institute (KEFRI) reveals that the tree could be used to mitigate the devastating impact of global warming.
The study aims to estimate the carbon sequestration ability of Kenya’s three-most common exotic tree species; the eucalyptus, pine and cypress trees, compared to one of the most common indigenous tree species in the same area – the indigenous cedar.
The study found that in Central Province, a one-hectare piece of land with 840 eucalyptus saligna trees sequestered 337 tonnes of carbon over eight years. Sweden, which was recently ranked the world’s top country in fighting climate change according to the 2012 Climate Change Performance Index, produces 50,600 tonnes of CO2 emissions a year.
“The result was determined by calculating the amount of carbon that had been sequestrated by Eucalyptus saligna and two other different types of exotic tree species, namely; Pinus patula (pine), which sequestered 99.4 tonnes of carbon in a period of 10 years, and Cupressus lusitanica (Cypress), which sequestered 73.3 tonnes of carbon in eight years. This was then compared to the indigenous cedar tree species grown in their favourite ecological zones,” said Dr. Vincent Onguso Oeba, the lead investigator of the study who also heads the Biometrics division at KEFRI said in an earlier interview.
“The indigenous cedar (Juniperus procera) in its best ecological zone in Central Province, with 587 trees on a one-hectare piece of land, was able to sequester only 55 tonnes of carbon in a period of 19 years,” said Oeba. However, the exotic eucalyptus tree has not received government nod's as such. In 2009, the then Minister of Environment John Michuki issued a directive that all eucalyptus trees growing near water sources in the country be uprooted in an attempt to lessen the impact of the country’s drought.
In Central Province, some farmers who had invested in improved eucalyptus tree species had no choice but to cut them down. However, Nyaga’s woodlot survived because it was more than 30 metres away from the nearest stream. The law allows for exotic trees to be planted in excess of 30 metres away from a watercourse that is more than two metres wide.
“If you plant eucalyptus trees near waterbeds, the roots will sense the presence of moisture, and will thus open the stomata very wide allowing a lot of water to be lost from the soil. But if the same trees are planted in a high-land area, they will sense the reduced soil moisture content, and thus close the stomata as much as possible to retain the little available water,” explained Muraya Minjire, a tree nursery expert working for the Tree Biotechnology Project.
At the moment, KEFRI is monitoring the carbon sequestration ability of 10 more indigenous tree species. “We are also in the process of developing internationally-accepted equations that will be used locally to accurately estimate the amount of carbon a given tree is able to sequester from the atmosphere at a particular age so that people who are involved in the carbon business will be able to understand the trade,” said Oeba.
According to the study, carbon quantification should be species specific in order to strengthen accounting systems for greenhouse gas emissions. “We also need to include the aspect of tree species in climate change adaptation policy,” said Oeba.