Your article (Planting billions of trees ‘best way to save planet’, 5 July) cites Tom Crowther, who led the research, as saying: “Personally, Brazil would be my dream hotspot to get it right – that would be spectacular.” And a dream it will remain until his exciting plan is rooted more firmly in global socioeconomic reality.

At the moment, far from replanting cleared land, Brazil is surging ahead with forest devastation on a frightening scale. Just-published official figures show an extraordinary 769 sq km, an area larger than the whole of Middlesex, was felled in June. The destruction of the Amazon forest, which Brazil successfully curbed after 2012, is roaring ahead again. Over 50% more trees were felled in June 2019 than in June 2018.

This is largely because Brazil’s president, Jair Bolsonaro, is an unabashed ally of agribusiness and is turning a blind eye to illegal deforestation. He reacted angrily to criticisms of Brazil’s environmental policies made by Angela Merkel and Emmanuel Macron at the recent G20 meeting. Earlier this week, he said he had flown over Europe twice and had not seen “even a square kilometre of forest”, adding: “They have no authority to discuss the environmental issue with us.”

But Bolsonaro cannot be blamed for all the problems. The Amazon forest is being cleared so that Brazil can produce more beef and soya to send abroad. Much of the trade is handled by multinationals. This will stop only if there is a major shake-up in the world food system. Consumers worldwide must stop eating food that is causing forest devastation.

Brazil’s thousands of indigenous and peasant communities have profound knowledge of the forest and would like nothing more than the power to protect it and replant devastated areas. But at the moment they are still being dispossessed. The first step in realising Crowther’s dream is to put an end to their expropriation.

Sue Branford

Clun, Shropshire

• Before we get too excited by this study, ponder the caution by its leader that it will take 50-100 years to have full effect – and reflect that the International Panel on Climate Change “warns that we have only 11 years to halve global emissions to meet their 1.5C target” (Letters, 28 June).

Peter Greaves

London

• Tree planting may have “mind-blowing” potential to tackle the climate crisis. However, the climate crisis is just one symptom of our continued destruction of the planet. The climate crisis has barely got going, but we are already in the midst of an extinction crisis that could soon rival that of the Cretaceous, when the dinosaurs became extinct. Today, we are losing species at a mass extinction rate, and at this point it’s nothing to do with climate.

Planting billions of trees will accelerate the extinction crisis, since closed canopy forest is not the natural state of most areas of continents. During the ice ages, and the intervening interglacials that dissected them, areas that we regard as natural forest today weren’t closed canopy, but instead were savannah or steppe, habitats that also absorb and store a great deal of carbon.

Covering these areas with closed canopy forest will reduce biodiversity and condemn many species to extinction – species that still survive in the remaining fragments of these habitats, or in the farmland that we have replaced them with. Planting billions of trees may be one way of solving the problem, but will create more. Perhaps we can just produce less carbon in the first place. We have the technology, and we know how to make it work.

Martin Dohrn

Bristol

• Your article reinforces the idea that the only way to get a tree or forest is to plant it. Creating woods in the way promoted by Defra grants and the Woodland Trust results in serried ranks of trees in plastic tubes that are often left long after they should be removed. Planting saplings grown abroad is almost certainly how ash dieback came to Britain.

Any piece of land, anywhere in the world below the tree-line, left alone without any human interference or expense, will undergo a natural growth via scrub to a fully mature forest of properly native trees. As it does so, it will be taking lots of CO 2 out of the atmosphere.

Whether the new forest is planted or natural, when it is mature it no longer has any good effect on CO 2 levels: the rotting dead leaves and fallen trees release exactly the same amount of CO 2 as the trees take in by photosynthesis. To make a mature forest a contributor to CO 2 reduction you need to cut down the mature trees and use the wood for building (or burn it to replace fossil fuels). Then let the felled forest regrow.

Dr David Corke

Director, Organic Countryside CIC

• I have been concerned about deforestation since I was a teenager. I specifically recall a national campaign in 1973, bearing the slogan “plant a tree in 73”. Sadly this didn’t have an impact beyond our shores.

Valerie Binsted

Cheadle, Cheshire

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