Why German trees are (and aren’t) dying

Pascal Bürkle

Hi, it’s Pascal, a developer at Datawrapper. This week I’ll take a walk through the German forests and look into why trees are dying and how bad the situation is.

Forests are essential to life. They serve as our world’s natural “green lungs,” providing homes for a wide range of other plant and animal species, supplying valuable timber resources, and offering protection against floods and landslides.

In the last 20 years our planet has lost more than 100 million hectares of woods, or about 2.5% of its tree cover. Deforestation and forest loss is an extremely big global problem, but due to a variety of factors it affects some countries a lot more than others. For this Weekly Chart I wanted to look at the health of the trees closest to me, in German forests.

Germany has about 90 billion trees covering an area of 11.4 million hectares, which is 33% of its total land area. That’s more than the global average of about 29% tree cover. Germany’s net tree cover is pretty stable, and has been for the past twenty years — also very different from the world at at large, which has lost about 100 million hectares of trees in that time. But, as we can see from this chart, there’s still a fair amount of gross tree loss happening in Germany. That’s what I’ll be looking at today.

Wildfires

One reason this topic has been on my mind is all the news in the world about wildfires. Often caused by human activity, they move about 6 meters per second on average and can have catastrophic effects on forests, wildlife, and people. In countries like Australia, Russia and Canada, fires are an extremely big problem and, along with agriculture, the biggest factor in the loss of tree cover.

In the last 22 years, 6,750 hectares of tree cover have been lost to fires in Germany. That’s about the area of Nuremberg, a city with a population of 500,000 people. However, to put this into perspective, Germany has lost about 1.23 million hectares of tree cover in total since 2001. This means wildfires are only responsible for about 0.5% of this loss, similar to other central European countries.

So wildfires are not a big problem for German forests. What does cause tree loss in Germany?

Heat, drought, and the beetles

Taking a look at this map, we can see that most tree cover loss in the past 12 years has been in central Germany, and especially in the state of North Rhine-Westphalia. Forests in this area date back to large-scale reforestation projects of the early 19th century and after the Second World War. These projects mostly planted conifer trees like pine and spruce, which were chosen for being robust, able to cope with difficult ecological conditions on clear-cut land, and providing high timber yields. Given the limited resources at the time, this was a great achievement.

The downside of these forests is that they are monocultures: All the trees have a similar age and general growth structure, which makes them much less resilient to pests. While deciduous trees like oak and beech can recover from infestations, conifers mostly can’t. To make things worse, intense periods of heat and drought make trees weaker but harmful insects like bark beetles stronger — and Germany, like many places, is getting hotter and drier every year. With the weak forests being unable to withstand the damage, sacrificing trees in a large-scale felling is often the last but most effective way to stop the spread by removing the bark beetles’ food source.

Between 2018 and 2021 the state of North Rhine-Westphalia lost more than 25% of its pine forests, in some parts even over 70%, due to the consequences of heat, drought, and pests. Other species like spruce (the second most common tree in Germany) and less common ones like sycamore and larch are also affected and show considerable damage.

Dr. Frank Thonfeld of the DLR Earth Observation Center (EOC) describes the situation as follows: “The annual forest survey reports drawn up by public authorities now make it evident that the condition of German forests has continuously deteriorated already for a long time. But the damage caused in the last few years is unprecedented.”

The current state

The numbers we looked at until now all are strictly presenting the loss. They ignore the vast amount of forest that is regrowing, naturally or due to active reforestation and replanting efforts. So in total the area covered by trees in 2000 and 2020 is very similar. However, the increased rate of loss and environmental changes in recent years is concerning and may become a problem if not handled well.

Fortunately, there are efforts being made to adapt existing forests to the new circumstances and improve their resilience to drought and heat stress. Every year, thousands of hectares of forest are converted from spruce or pine monocultures to mixed forests with a broader structural and genetic diversity. Decreasing the amount of resinous trees (like pine and spruce) also reduces the risk of forest fires.

Another good sign is that our forests are growing older than before, with 24% of trees being older than 100 years and 14% being older than 120 years. The mean tree age of 77 years has risen by about 4.5 years since 2001.

If you’re interested in exploring the data in detail yourself or checking out other countries, head over to globalforestwatch.org, which has great visualizations and a lot of data.

That’s it from me for this week! I hope you found this little forest exploration interesting. We’ll see you next week!

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Pascal Bürkle

(he/him, @pabueco) is a full-stack developer working on various aspects of the Datawrapper app. In his spare time, he loves exploring random ideas, starting way too many side projects, and playing all kinds of video games. You can see more of his work at his website pabue.co.

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