All that's green is not gold - Frans-Jan W. Parmentier

At the failed climate summit in Madrid it became, once again, abundantly clear that international climate policy is completely dysfunctional. After 25 climate summits, global emissions are still rising, while they need to be reduced by at least 7% per year in order to avoid global warming of 1.5 degrees – which the World Meteorological Organization reported before the climate summit.

Incidentally, the biggest problem with the negotiations was not that there are countries which deny climate change. No, that's an exception nowadays. It's much simpler: while everyone speaks highly of saving our climate, there is no one who wants to pay for the costs. In search of cost-effective ideas, the widespread planting of trees is often presented as a universal remedy to all our problems. Forests absorbs CO₂ without having to pay much attention to them, and at the same time you can sell it to the public as nature restoration. Last week, the EU announced this as an integral part of the "European Green Deal". If the extra wood production can be used for environmentally friendly solutions such as biofuel, perhaps it's even possible to make a profit. You can't imagine a brighter green future, right?

The climate potential of tree planting does appear huge. A study in the scientific journal Science last summer claimed that newly planted forests could capture a quarter of all CO₂ present in the atmosphere. Unfortunately, the study appeared to have overlooked a number of important issues, and the potential was overestimated by a factor of five. Dozens of prominent scientists recently criticized the study in the same journal. They highlighted two main issues that are all too often forgotten by the proponents of forest as a cheap climate measure.

It really matters a lot where you plant a tree, for two main reasons: snow cover and soil type. Anyone who has stood on a snow covered field on a sunny day knows that this is blinding to the eye. But if you plant a forest in the same field, the dark tree trunks absorb sunlight. We call this difference in the reflection of sunlight the albedo effect. Conifers are the worst, since at least deciduous trees lose their leaves in the winter. During the dark winter, the albedo effect is not a big problem, but there are also tree planting programs in places such as Greenland where snow cover can last well into May, when there is plenty of sunlight. This is also the case in the mountains and in northern Scandinavia. Planting a forest in these regions can lead to a local warming that offsets the climate benefit of the extra CO₂ uptake.

But the most important advantage of tree planting, the CO₂ gain, does not apply everywhere either. The soils of the world hold much more carbon than all the trees combined. Peatlands have particularly carbon-rich soils, but in the past many of them have been drained to be able to plant forests. When this is done, a lot of CO₂ is released from the soil, instead of being collected. The planting of trees can also negatively influence the balance between soil and atmosphere in grasslands or heathlands. Moreover, these are unique ecosystems that are essential to stop the loss of biodiversity. It is therefore a much brighter idea to better protect the nature that we already have than to replace it with a forest that we do not need.

Because Europe's forests are already doing well, and Norway is no exception. Calculated in volume, there are three times as many trees in Norway than a century ago. Because of the high demand for wood in the past, most forests had been thinned out, which is why many new trees were planted in the mid-20th century. Now, decades later, they are still increasing in size. Also, global warming has caused the tree line in the mountains to go up, and many hut owners have lost their view because of the encroaching forest. No, we don't have a shortage of trees.

Trees can make a modest contribution to solving our climate problems, but planting them randomly can do more harm than good. Moreover, a misleading representation of forest as the ultimate climate solution can also be counterproductive – if it is misused as an excuse not to reduce fossil emissions. Because that's where the solution to the climate problem lies: that we tackle it at the root.