Making tree-planting count

Political gimmick or killer app for Africa’s climate? It depends on the way you do it. 

The news: Kenya took the unusual step of declaring a national holiday this week to plant 100 million trees – two for every citizen. 

• The government supplied 150 million seedlings in public nurseries.

• Software recommended species by location and monitored progress.

Numeric ambition: Few could fault Kenya’s goals.

• Plant 15 billion trees by 2032

• Increase national forest cover from 7% to 10%

The logic: Tree planting can have massive benefits in terms of carbon storage, soil preservation, biodiversity conservation and livelihoods for local communities. 

• Forests support the livelihood of 1.6 billion people worldwide in timber harvesting, other forestry products and tourism. 

• John Clark, CEO of Tupande by One Acre Fund, said, “Trees are one of the most important livelihood assets for a farmer.” 

Quality matters: What’s often overlooked is that tree planting has its pitfalls.

• Will the trees live long enough to store significant amounts of carbon? 

Survive & thrive: Best practices are hard to follow on colourful mass activations.

• Local residents need to look after the trees for decades, so best to get their buy-in. 

• Paying local communities for maintenance reduces incentives to cut down trees. 

• Figure out beforehand what grows well where, and when it should be planted. 

• Avoid monocultures to ensure biodiversity and sustain supportive ecosystems.

• Trees need enough water – best to figure out supply and infrastructure. 

The backlash: When such practices are ignored, the result is often damaged ecology.

• Reducing biodiversity

• Threatening water supplies

• Making ecosystems less resilient

• Speeding extinctions by introducing competing foreign species

• Increasing temperatures as some trees absorb more heat than grasslands

Not new: In the 19th century, South Africa planted Australian acacias to stabilise dunes and produce timber. But they lowered the water table and even depleted it in places.

• The country now spends millions of dollars every year to remove them. 

Complex dynamics: Determining when tree-planting removes carbon can be difficult. 

• Existing ecosystems in open areas may already function as carbon sinks. 

• When one then plants trees, this might only add marginally more carbon storage.

• In some cases, land clearing and frequent tree harvesting in fact lead to a net negative impact. 

Done right: The Great Green Wall project across 20 countries in the African Sahel once aimed to fight desertification by planting a continuous line of trees.

• But maintenance turned out to be near-impossible in vast uninhabited areas.

• The project adapted and became a mosaic of green land use practices managed by local farmers instead.