The planet’s 3 trillion trees anchor complex ecosystems and suck up 30% of carbon emissions from burning fossil fuels. That’s why there are calls for mass tree planting to cover 25% more of Earth’s surface, and governments have pledged to add a trillion new trees. Stewarding existing forests is an important climate solution, but planting trees to cancel out emissions is not. Targeting farmland for tree planting triggers food shortages, forced migration, and violent evictions of Indigenous peoples. Corporations and governments won’t invest in expensive carbon reduction projects when they can win public favor and pay for their carbon sins by planting trees instead.