19 Mar 2019 Story Ecosystems and Biodiversity

Learn about the value of indigenous trees—and plant one!

Photo by Michael Muratha

“This tree grows on one mountain in Malawi and there are hardly any left,” says botanist Mark Nicholson, manager of a remarkable 40-hectare forest near Nairobi, Kenya, planted with over 650 species of indigenous trees and shrubs.

“Almost everything here in the forest, including what are now large trees over 20 metres high, has been planted since 2000, and we’ve seen a big increase in biodiversity,” says Nicholson. “When we first came, all the trees were exotic, non-native species, like cypress, wattle, eucalyptus and pine. We recorded only 35 species of birds. Now that number is up to 187 and in 2015 the colobus monkeys came back after an absence of 80 years. They came back because indigenous trees provide food for them.”

In the lead-up to the International Day of Forests on 21 March, UN Environment is collaborating with Nicholson and his Plants for Life International, a non-governmental organization, to raise awareness of the importance of indigenous trees for local ecosystems. On the day itself, the UN-REDD Programme and Plants for Life will have a stand on the UN compound in Nairobi with hundreds of tree seedlings comprising 12 different species of indigenous trees. UN staff and their families will be encouraged to sponsor tree-planting or take away and plant seedlings in their gardens or school compounds.

“The theme of the International Day is ‘Forests and Education’, and our aim is to get a message out that indigenous tree and shrubs are vital for healthy biodiversity and human well-being,” says UN Environment ecosystems expert Tim Christophersen.

Brackenhurst seedling propagation area: some seedlings can take over a year to germinate. Photo by Michael Muratha

Some trees “fix” nitrogen while others produce quality mulch, which enriches the soil. Other woods can be ideal for carving or produce high-quality timber. Certain species of indigenous olive trees, for instance, don’t produce olive oil but make excellent furniture. Many people are unaware of the medicinal value and income-generating capacity of some indigenous tree species.  

UN Environment and the Food and Agriculture Organization of the United Nations are leading the recently announced implementation of the UN Decade of Ecosystem Restoration 2021-2030, which will require a massive expansion of successful pilots such as the Brackenhurst restoration effort.

The Bonn Challenge is a global effort dating back to 2011 to bring 150 million hectares of deforested and degraded land into restoration by 2020. By now, countries have already pledged even more: 170 million hectares (as of February 2019) and 350 million hectares by 2030. As part of the Challenge, Kenya is aiming to plant trees on 5.1 million hectares of degraded land—an area the size of Costa Rica. Kenya’s official replanting policy recognizes the importance of planting indigenous trees.

All UN programmes and agencies are signed up to the 2030 Sustainable Development Goals. Goal 15 is set to “protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss.”

The UN-REDD Programme, a collaborative programme on Reducing Emissions from Deforestation and Forest Degradation in Developing Countries, was launched in 2008 and builds on the convening role and technical expertise of the Food and Agriculture Organization of the United Nations, the United Nations Development Programme and UN Environment.

Prunus africana leaves are highly medicinal for BPH (benign prostatic hyperplasia). Like almonds, they contain small and harmless amounts of cyanide. Photo by Michael Muratha


Plants for Life is a member of Botanic Gardens Conservation International, the world's largest plant conservation network.

Nicholson’s forest, known as Brackenhurst Botanic Garden, is about 2,000 metres above sea level and 30 kilometres north of Nairobi.

“The exotic trees that were planted here previously grow so fast that they extract large quantities of soil water. They dry up the soil, and so streams can run dry for several months a year. Now, thanks to all the indigenous trees we’ve planted, we have streams all year round,” says Nicholson. “We’ve recorded a lot more species of animals, birds, butterflies and other insects over the past 18 years.”

He lists his main goals as ecological restoration, biodiversity conservation, and income generation, including from understorey coffee, indigenous vegetables, and offcuts in a country desperate for fuel wood.

“Indigenous African ebony has been almost wiped out because no one plants it,” says Nicholson. “It’s sad to see 400-year-old specimens being cut down. If Kenyans take a long-term view and plant trees for their grandchildren, they will leave a valuable legacy.”

Did you know there are over 600 species in the Euphorbia family in East Africa? Some of the large Euphorbia trees live in dry areas so they have lost their leaves altogether in response to water stress and photosynthesize only through their stems.

Education and research are a key part of the work of Plants for Life. Brackenhurst runs courses on ecological restoration, plant propagation, botanical identification, ethnobotany, floristics and invasive species control.

The seed propagation area boasts several hundred seedlings of Widdringtonia whytei, the extremely rare “hard softwood” tree from Malawi mentioned by Nicholson. “We will grow these as part of our ex situ conservation programme:  when a plant is endangered in its place of origin (in situ), one tries to grow it in other safer places.”

For further information, please contact Tim Christophersen, head of UN Environment’s Freshwater, Land and Climate Branch, and Chair of the Global Partnership on Forest and Landscape Restoration: Tim.Christophersen