Political parties in developed countries have made various promises to plant billions of trees. And many private companies have also got in on the act. EasyJet has promised to plant as many trees as required to offset its carbon emissions by 100%. Trees have become environmental superheroes. And we can understand why: as they grow, they become carbon sinks. So trees have become a painless solution to climate change for many experts. According to a study, planting 3 trillion trees worldwide would be enough to absorb two-thirds of carbon emissions generated by human activity, without eating into farming land or pasture. This theory has been questioned by recent studies. Forests would be less effective carbon sinks than we think. They could even make carbon emissions worse. The dark colour of forests could actually warm the ground which they cover. In addition, some volatile organic particles produced by trees to attract pollinators could transform into greenhouse gases. Other particles interact with car emissions, making global warming worse. This does not mean that we should stop planting trees, but we need additional policies like reduced consumption of fossil fuels.