The 21st March is the International Day of Forests, an awareness day established by the UN Forum on Forests and the Food and Agriculture Organisation, aimed at improving understanding of the importance of forests, and what we can do to maintain their diversity and integrity.

Forests are home to about 80% of the world’s terrestrial biodiversity, with more that 60,000 tree species, and around 1.6 billion people directly depend on them for food, shelter, energy, medicines and income, with the rest of the global population indirectly relying on them for the very air we breathe. The world is losing 10 million hectares of forest each year – about the size of Iceland – which accounts for 12% to 20% of the global greenhouse gas emissions that contribute to climate change. Land degradation affects a further 2 billion hectares – an area larger than South America – increasing the forests’ vulnerability to climate change.

The UK government has planted millions of trees over the last decade and is pledging to plant another million between 2020 and 2024, in an effort to improve biodiversity and sequester carbon. However, Friends of the Earth said this fell far short of what was needed to have a real impact on climate change. It’s important to understand the real effects of carbon offsetting via tree planting, its unintended consequences and potential limitations.

Do they provide an ‘everyone wins’ climate solution? Who do they benefit? Do they have the potential to cause harm? How effective even are they?

Tree planting and carbon offsetting

Carbon offsetting is a way of paying for others to reduce emissions or absorb CO2 to compensate for one’s own emissions. This can be via tree planting, or funding projects using green energy (which may otherwise have used fossil fuels). Tree planting is now being provided everywhere, from holiday-providers to delivery services and beyond, with a myriad of companies claiming to offset emissions with a range of different schemes. 

Many studies suggest that planting trees is one of the more effective ways of tacking land degradation and absorbing excess CO2 from the atmosphere. The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) estimated in 2018 that at least 10% of human-induced greenhouse gas emissions derive from deforestation alone, and other studies have suggested that reforestation could remove three billion to 18 billion tonnes of CO2 per year. In 2017 land use changes – mostly deforestation – contributed four billion tonnes of CO2 emissions to the global total of 41 billion tonnes of CO2. If we stopped cutting down trees in the first place, our annual emissions would be reduced by around 10%. These are all significant numbers.


However, many experts are concerned that offsetting projects don’t lead to the behavioural change we really need to see if we want a palpably different future than the one projected. Offsetting has been shown to encourage people to continue with behaviour they know is harmful, and allows the worst polluters like BP and Shell to continue with unsustainable behaviour, while simultaneously shifting responsibility onto the consumer to reduce damage. Heathrow, too – which hopes to take an extra 265,000 flights a year with a third runway – has stated that it plans to use offsets to make it “carbon neutral” by 2030 and to be “zero-carbon” by 2050, even though it will be directly responsible for releasing millions of extra tonnes of CO2 into the atmosphere with the plans. 

Planting trees, while vital in many areas, cannot be a replacement for not producing emissions in the first place. Due to trees’ slow-growing nature, it can take as many as 20 years to capture the amount of CO2 that a carbon offset scheme promises with the click of a button. Tree planting is not the ‘rapid-response’ action we need when it comes to climate change and GHG emissions – it plays a role in reforesting areas that we can previously deforested, and in mitigating the long-term effects of climate change. However it can only provide a fraction of the carbon reductions needed to keep temperatures below the 1.5C to 2C goals, and must be used in conjunction with behavioural change and other faster-acting climate solutions. 

Concerns have also been raised about the issue of climate colonialism, which has been defined as “the domination of less powerful countries and peoples by richer countries through initiatives meant to slow the pace of climate breakdown”. Carbon offsetting projects, such as tree-planting schemes, are cheaper to set up in the Global South rather than closer to home (which is in as much need of reforestation as anywhere else). Because of this, there is a lack of connection between the people paying for the projects, the companies providing them, and the local people on the ground, including Indigenous People. For example, Amnesty International reports that the Sengwer people of Embobut forest in Kenya were violently forced from their homes and dispossessed of their ancestral lands as part of a government plan to reduce deforestation. The Sengwer people were moved without being consulted, and never consented to the plans for their removal – a violation of both Kenyan and international law. The world’s 370 million Indigenous Peoples make up less than 5% of the total human population but manage over 25% of the world’s land surface and support about 80% of the global biodiversity. Extra pressure in the form of ‘doing good’ from overseas can exacerbate their persecution and expedite ecosystem degradation, rather than the opposite. Climate justice requires an in-depth understanding of the needs of local peoples, and offsetting schemes often do not have this knowledge. Saving the planet cannot come at the cost of the people living on it.

Theoretically, so long as local people are consulted and suitable regions identified for reforestation, tree planting can have positive effects, but only if the right species are used. Many of the trees being planted are monocultures of fast-growing species – useful for carbon sequestration, but provide next to no ecosystem benefits. Biodiversity, or species richness, is crucially important for the success of these projects, provided the species are of local origin and not invasive. Regardless, a large body of literature shows that even the best planned forest restoration projects are unlikely to fully recover the biodiversity of intact forest, which in many cases have taken thousands of years to establish. This shows the importance of preserving what forest we have left, and only reforesting in addition to other measures to address the key causes of deforestation. Prevention is better than cure. 


It is evident that our forests are crucially important to the survival of our planet, and the rate at which we are deforesting the planet, many things need to be done to preserve what we have left and restore what we have broken. Tree-planting carbon offset schemes, however, have limitations due to intrinsic factors, such as how slowly trees grow, to their impact on local communities and species diversity. 

When choosing a carbon offsetting scheme, ask yourself the following questions:

  • Am I doing this to offset guilt as much as carbon? Could/should I avoid doing this polluting activity in the first place?
  • Are the trees native and will they support biodiversity?
  • How long before the trees will absorb the amount of CO2 that the organisation promises? Will they be protected for the decades it takes?
  • Who is planting the trees? Are they being paid/treated fairly?
  • Who is encouraging this offset? If it is an oil or gas company or an airline, think about why they are doing this and what you can do to reduce fossil fuel use in the first place.
  • Look for projects supported by the Gold Standard to quantify and certify impact in line with the UN’s Sustainable Development Goals.