Award-winning British science journalist Fred Pearce has written about the environment and climate change for 40 years but remains optimistic.
In his book A Trillion Trees - How We Can Reforest Our World, Pearce argues that if we give it room, nature will restore itself.
A trillion more trees in the world could undo much of the damage deforestation has done, Pearce tells Kathryn Ryan.
Despite gloomy headlines, quite a lot of reforestation is already happening.
“In lots of places forests are starting to regrow, usually because farmers are abandoning farmland, it's happening quite a lot in Europe, particularly Southern Europe, where populations are getting quite old, and people are abandoning their farms.
“In Eastern Europe where the old collective farms disappeared after the collapse of the Soviet Union, people again just walked away.
"Even in parts of Africa where people are moving to the cities and leaving behind farms. Wherever people abandon farms, trees come back,”.
This trend gives Pearce hope.
“Because nature is still strong. We talk about 'fragile nature', but actually, I don't buy that, nature is quite strong, nature will come back. And the more we give nature a chance to do that by just giving room really, it'll happen, we can have a trillion more trees.”
We can let nature do the heavy lifting, he says.
“We can put trees in the wrong places if we get very obsessive about planting trees. We go around planting, trying to plant trees, in deserts or on grasslands and we destroy a lot of ecosystems doing it.
“Nature has been busy working away at this for millions of years, nature does know about planting trees and about restoring forests and it's what nature does, it's adaptable.
“If the circumstances change, then different seeds will germinate, and different trees will grow.”
There is plenty of available land on which we can allow this to happen, Pearce says.
“There is a lot of land; messed-up forests, degraded forests, forests that have been partly logged and left behind, a lot of former farmland, there is an awful lot of land … we have enough land for a trillion trees.”
Costa Rica is a reforestation success story, he says.
“Thirty years ago the president decided that he was going to stop destroying the forests to create pastures to grow beef to sell to American burger chains, which is what was happening in that country, and to restore the forests.
Costa Rica had previously been a leader in deforestation, with forest cover dropping from 70 percent of the country down to about 20 percent.
In the 1980s, the government started giving landowners incentives to put in trees or let them re-grow, Pearce says, and now there is 70 percent tree cover again.
Those landowners now making a living from eco-tourism, he says.
“A lot of Europeans in particular, go to Costa Rica to enjoy the rainforest on eco tourist trips, few of them realise that the forest they go to see was cattle pasture just 20 years ago.”
This “amazing transformation” can happen anywhere, and it must, Pearce says.
“We used to have 6 trillion trees, now we're down to 3 trillion. We need to get at least 1 trillion back, we have room to do that.
"But a trillion is a big number that would require 1000 trees every second for the next 30 years. It would be a huge industry, a very disruptive industry if we decided to plant them all.
“So let's let nature do it. And also, let's let local people who know about their land and about their trees and about their forests be in charge of it.”
In A Trillion Trees, Pearce looks at various parts of the world where humans have retreated and nature has famously returned, such as Chernobyl.
“Where humans, for whatever reason, walk away, whether it's a big radioactive disaster, toxic landfill or we just simply abandon farmland or whatever it is, wherever we step back and give nature room, forests will restore themselves, sometimes different forests from the one that we once that we had before.
“But forest will generally restore themselves. And that, for me, is a really important truth. Nature can recover.”
Fred Pearce has been the New Scientist environmental consultant since 1992 and is a contributor to The Guardian and The Washington Post.