Planting forests for climate change

As well as cutting carbon emissions to limit climate change, scientists in Switzerland have reported that increasing the amount of forest on the planet should also be a major priority. According to calculations, 1 billion hectares of new forest would lock away over 200 billion tonnes of carbon: that’s enough to keep temperature rises by 2050 to within 1.5 degrees Celsius. But have we got the space for all these trees? And can this really work? The new study suggests that we do and it can, but we need to act fast. University of Connecticut ecologist Robin Chazdon, who wasn't involved in the work, took a look at the figures for us...

Robin - Bringing back about one billion hectares of forest cover would help to limit the effects of global warming to only 1.5 degrees by 2050. This would be additional forest cover because we have lost a tremendous amount of forest cover already.

Chris - What's the proposed mechanism? Because a forest is only a temporary stopgap, isn't it, in the sense that a tree pulls some carbon out of the atmosphere, granted. But, as soon as that tree gets burned or it rots down, the carbon goes straight back into the atmosphere so it's not a permanent way of sequestering carbon like the coal and the oil that we burned and then released the carbon from in the first place...

罗宾-这是真的。但是当你恢复一片森林you have more than one tree and you have trees that are continually growing over time. So even if individual trees may die you have new trees coming up, and after that forest reaches an equilibrium point then you have more long-term or almost permanent storage unless some disaster happens.

Chris - So how does this sit with what we anticipate human population is doing? Because the reason at the end of the day that we have declining forest cover, is chiefly because humans have gone in there with chainsaws.

Robin - Exactly. I think we need to consider this from a very holistic perspective. In addition to protecting what forests currently remain on our planet we need to find ways to continue to source our products without further deforestation, and we need to replenish forests on land that has been cleared and is currently being used for crops or for grazing land.

Chris - But the human population's going up not down and we can't even feed the ones we have got at the moment. And so you're advocating, or this paper is advocating that we pull even more land back and turn it back into forest, as well as, in some way, feeding an increasingly hungry population?

Robin - I think the key is that, first of all, not all of the cleared land in our planet is being used effectively to produce food and not all that food is getting to the people who need it. It's not just a matter of creating more forests and protecting them, it's also a matter of improving the delivery of agriculture, the sustainability of agriculture, and the distribution of food to needy people.

Chris - So this group are advocating that we need about a billion hectares more forest than we currently have, and that includes recouping some of what's been lost, but does that prediction also take into account land loss owing to climate change? Because if one looks at the models of what we think climate change is going to do to the planet we think that the available land area that we can depend on is going to shrink.

Robin - Yes. And if we don't act quickly to begin to restore the tree cover it's going to become virtually impossible in the future because climate change is already affecting the ability of trees to grow and the ability of forests to remain. And the simulations done in this paper highlight the urgency of beginning restoration and reforestation now. But I would caution that we don't need quick fixes, we need quality fixes. We need intelligent planning and we need to think about the social and economic issues as well, because the new forest cover that we need, needs to endure and it needs to be beneficial. It's not just a question of throwing trees on the ground and planting trees and wishing for the best. I think there's a huge array of social issues and economic issues that also need to be confronted as part of this activity.

Chris - And are people, do you think, politically, internationally on board with this?

Robin - Well, we do have many obstacles and certainly our political leadership in many countries is putting obstacles in place. But there are many grassroots efforts and there are many international organisations and programmes that are getting countries on board. For example, the Bonn challenge which has over 47 countries that have made commitments for restoration within their countries. Over 170 million hectares have been committed and I think as scientists we need to point out what we need to do and how we can do it.