Photo: Kim Pilegaard

Ten-year journey towards a warm future comes to an end

Friday 20 Mar 15
by Marianne Vang Ryde


Teis Nørgaard Mikkelsen
Associate Professor
DTU Environment
+45 21 33 13 94


Kim Pilegaard
Professor Emeritus
DTU Environment
+45 40 25 68 39
For the past ten years, a hill in Jægerspris, Denmark, has been on a trip through time to 2075—but it’s all over now. The researchers have both good and bad news.

In 2005, it was just a grass and heather-clad hill in the middle of the Jægersprislejren military facility, where young soldiers could train their shooting skills. But then it was loaned out to researchers from Risø National Laboratory for a unique experiment intended to demonstrate how ecosystems respond to the anticipated climate change.

The good news is that the ecosystem proved to be highly robust. The bad news is that the plants’ roots grew so quickly that in the long term, the continued growth of the plants is likely to cause an increase in the release of carbon from the soil.

Twelve octagonal plots, each measuring seven metres in diameter, were encircled by pipes that could be used to carry CO2; awnings were set up so that some of the plots could be subjected to protracted periods of heat and drought; and walkways were installed to connect all parts of the installation and allow staff to access and repair the system without setting foot on the ground.

“We wanted to examine a natural ecosystem, but the simple fact of our setting up a scientific experiment meant that it could not remain completely ‘untouched’. Before we arrived, the Danish Armed Forces had kept the area clear of trees, and we continued this practice. The wildlife underwent some changes as well, because the awnings proved to be perfect ‘air raid shelters’ for mice,” relates Teis Mikkelsen, Senior Researcher at DTU Chemical Engineering.

"The ecosystems are robust. There’s no doubt they’ll adapt. Mankind will suffer the greatest impact from the climate changes."
Professor Kim Pilegaard, DTU Chemical Engineering

Three in one
The reason why this particular hill was so well-suited to a climate experiment is that it primarily featured two plants, each with its own pattern of life. Heather can live for up to 30 years, and succeeds to some extent in adapting to changes that it experiences during its lifetime. Grass has a much shorter regeneration period and therefore applies a more ‘opportunistic survival strategy’, as the researchers term it. If one generation withers and dies, a new generation replaces it as soon as the moisture returns.

The plots were carefully chosen according to the distribution of the two primary plants, and they were then given a severe dose of climate change: more CO2, higher temperatures, long periods of drought—or all three at once.

“Nowhere else in the world have researchers conducted such a comprehensive experiment, where natural areas were subjected to all three changes at the same time. Testing each parameter separately wouldn’t have provided any information about the combined impact, because it’s impossible to calculate possible synergetic or antagonistic effects,” explains Teis Mikkelsen.

Good and bad news
The ecosystem is robust—in any case, the plants can survive the moderate changes they were subjected to in this experiment. However, they develop a broader network of roots, and when they receive additional CO2, it provides extra nutrition for the microbes in the soil. This, in turn, means they can convert more organic matter, and at the end of the day, this results in more carbon being released from the soil.

“The result is that the net binding of carbon is halved, leading to an additional increase in carbon dioxide levels in the atmosphere,” says Professor Kim Pilegaard from DTU Chemical Engineering, laying out the rather disappointing conclusion.

It is, however, positive to note that the microscopic worms (enchytraeidae) that regenerate extremely quickly—just like the grass—proved to be extremely adept at adjusting to the climate changes. Then again, that does little to remedy the overarching problem.

“The ecosystems are robust. There’s no doubt they’ll adapt. Mankind will suffer the greatest impact from the climate changes,” says Kim Pilegaard.

Unfortunately, climate change is powering away at an even greater pace than anticipated ten years ago, so there is every reason to run new experiments.

Article in DTUavisen no. 3, March 2015.

The Climaite experiment

Photo: Teis Mikkelsen
The Climaite Project was officially inaugurated on 3 October 2005 by Connie Hedegaard, Danish Minister for the Environment at that time. The experiments have cost upwards of DKK 100 million, of which the Villum Foundation covered DKK 53 million. The remainder was contributed by the participating universities, research councils and the EU.

DTU led the project, with research teams from the University of Copenhagen and Aarhus University participating.

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