The Chinese company building the multimillion-shilling Nairobi Expressway has until the end of March to plant 3,000 assorted seedlings along the 27km stretch.
Environment watchdog Nema wants China Road and Bridge Corporation (CRBC to ensure that trees felled during the project are replaced.
The order to CRBC took effect last month, Nema Director-General Mamo Boru Mamo said.
The project led to the cutting down of at least 2,500 trees, he said.
“Under the provisions of (the environmental impact assessment), we have directed the Chinese company to undertake greening up of Nairobi Expressway,” he said.
“We estimated that they had removed 2,500 trees during the construction and we want them to plant at least 3,000 assorted tree seedlings to replace the tree cover lost during the construction process.”
The greening will go hand in hand with a beautification programme already underway.
At least 13 different species of trees were lost to make way for a four-lane dual carriageway that starts in Mlolongo and ends at the James Gichuru junction in Nairobi.
“We have directed them to undertake the greening in addition to the beautification programme using tree seedlings, especially on the wayleaves,” he said.
The construction of the expressway led to the loss of biodiversity in the capital city, with some environmental groups saying more than 4,000 young and mature trees were cut down.
The contractor was supposed to plant trees elsewhere – five trees for every one cut down – to replace the lost vegetation, said the Kenya National Highways Authority.
“We expect that the trees will mitigate noise pollution and also provide required environmental service and also improve aesthetic value of the environment and reduce the concrete jungle,” Mr Mamo said.
The seedlings, he said, must be in line with the Kenya Forest Service guidelines in order to avoid introducing invasive species.
“They have three months to have the seedlings in place. We know they have already engaged clients and we will have routine monitoring of the seedlings they will be planting, which have to meet KFS guidelines,” he said.
Nairobi has over the years lost its vegetation due to encroachment and infrastructure development such as roads and buildings, resulting in a decline in forested land and green spaces.
Different reports have said that the city lost 22 percent of its green spaces between 1988 and 2016.
