The role of nature in fighting the climate emergency has been one of the biggest environment stories of this year. That’s because scientists no longer believe that emissions reductions will be enough to limit global heating to the 1.5C to 2C promised in the 2015 Paris agreement. That means that as well as limiting future emissions, we must focus attention and resources on finding ways to draw greenhouse gases that have already been released out of the atmosphere.

Carbon capture and storage (CCS) has long been viewed as an important tool. Increasingly, however, scientists believe that natural climate solutions could prove more effective than technological ones. A recent paper calculated that restoring nature could provide a third of the CO 2 reductions needed by 2030 to keep heating below 2C, and in March the UN declared that 2021-30 would be a decade of ecosystem restoration. In the UK, the Committee on Climate Change advised the government that to meet its goal of net zero carbon by 2050, 107 hectares (267 acres) would have to be planted with forest every day: perhaps 1.5bn new trees in all.

This is the background to the choice of trees as the theme for this year’s Guardian and Observer charity appeal. At the end of a tumultuous 12 months of environmental politics, during which the Guardian and the UK parliament were among organisations to declare a climate emergency, we are offering our support, and that of our readers, to four charities that are doing what we believe to be some of the most important work in the world. Last year, thanks to the incredible generosity of readers, we raised £1,127,000 for charities working on immigration issues in the wake of the Windrush scandal. As the Guardian’s editor, Katharine Viner, and colleagues prepare to take donations over the phone in our annual telethon on Saturday, we hope for an equally impressive result.

Stories about rewilding, ecosystem restoration and the school strikes movement have provided much-needed hope to people dispirited by the lack of climate progress globally. But the news from Brazil, where rainforest deforestation is once again accelerating and actively promoted by the president, Jair Bolsonaro, could not be more disturbing. The Amazon is the world’s biggest carbon sink and the threat that its destruction represents is existential. So while three of this year’s charities – Trees for Cities, Trees for Life, and the Woodland Trust – work in the UK, Global Greengrants Fund UK will use donations to protect the Amazon, through a network of grassroots relationships with the land rights and indigenous activists at the forefront of this struggle.

Just as defending the Amazon is about people as well as trees, any project to increase tree cover in the UK must involve communities as well as landscapes; Trees for Cities specialises in deprived areas and neglected city spaces. Wherever they are planted, or allowed to regrow naturally, trees must not be viewed as a panacea – or allowed to become a displacement activity or greenwashing tactic. The overwhelming climate priority remains drastic cuts in emissions – 7.6% annually, according to the UN. But the palpable enthusiasm for rewilding, and tree planting, that has taken root over recent months deserves to be nurtured. As opinion polling also shows, increasing numbers of people understand that nature is endangered, and want to mend it. Our Christmas appeal seeks to harness this spirit of reparation.

Telethon phonelines are open 10am-6pm (GMT) on Saturday. Call 0044 203 353 4368 or donate online here