Trees growth rate has increased!

Since 1870, Forests growth in Central Europe has accelerated. This might be due to climate change. According to a study conducted across Europe, trees have experienced a faster growth but with lighter woods.

Trees growing at a faster rate seems to be a great news. This could take in a lot of carbon dioxide and reduce global warming. Increase in wood volume would meet the growing demand for wood. But can climate change actually contribute to good? Well, a team led by Prof. Dr Hans Pretzsch from Technical University of Munich (TUM) analyzed wood samples and reached a surprising conclusion.

In the study, the researchers analysed wood samples from the 1870s to this year with the modern measurement technology. Annual rings and wood density of the samples were measured high-tech procedures. The team concluded that the annually growing wood has gradually become lighter by up to 8-12% since 1900. Simultaneously, the volume growth of the trees in central Europe accelerated.

Which means: Even when the volume of wood produced increased, it contains less solid materials than decades ago. 

What is the Problem with Lighter Woods?

The advantage of lighter wood is their weight. But, it has less solid and low calorific value. Compared to conventional woods, these woods might not be suitable for many applications like construction and energy production. Lightweight wood in trees increases the risk of damage like breakage due to the wind.

Basically for a tree with a  given stem diameter, wood strength, energy content, C-sequestration ability and stability against wind has reduced. The increased early wood fraction suggests that change in season behaviour could be the main cause.

But the major concern is that we could overestimate the current carbon sequestration of the forests if calculated with conventional wood densities. “The accelerated growth is still resulting in surplus carbon sequestration”, says Prof. Pretzsch.

So, current increased wood volume growth rates must not be straightforwardly converted into carbon sequestered. Because the traditional estimate would be too high by about ten million metric tons of carbon per year. 

Which means: we can falsely believe that carbon dioxide is decreasing at a rapid rate, but no. Monitoring and remodelling utilization of carbon and biomass in forests could help avoid such miscalculations.