Grafenau, Mariana Schroeder, Sept. 2, 2003

 

The Forest is Regenerating after Germany's Worst Spruce Bark Beetle Attack

 

The Spruce Bark Beetle has destroyed nearly 4000 hectares – nearly one-sixth of the Bavarian Forest National Park in southern Germany. Because of the enormous area of destruction and because park officials have decided not intervene, but to leave the forest to its own devices, this national park has attracted international attention. Now more than 10 years since the last spruce bark beetle attack, the forest is regenerating and the destruction is slowing down.

 

From afar, huge sections of forest, stretching to the horizon appear lilac-gray. When you enter the forest, giant trees litter the ground, along with their broken branches. Those still standing are broken in half – rotting wood as far as the eye can see. But the forest is not dead. Beneath the trunks of fallen trees, young spruce have already started building a new forest. Beech, mountain ash and other deciduous trees are also growing in the areas cleared by the bark beetle.

 

Hans Kiener, head of the  Department for Nature Conservation of the Bavarian Forest National Park, says the new mountain mixed forest will be far superior to the old spruce wood stands that it replaces. “When you look to this area 20 years ago we saw a beautiful spruce forest – green and vital -- but this spruce forest was not natural. It was man-made, tended for hundreds of years by the foresters. What we can see now is that the new generation of trees is of different ages and is mixed like a mosaic. We can expect the new generation will be more resistant to the bark beetles which affected the old stand of trees before.”

 

The spruce bark beetle is less than 6 mm long. It only attacks spruce trees and bores through the bark to feed on the layer of tissue right beneath it, the cambium. These tissues carry nutrients from the foliage to the roots and water from the roots to the foliage. Bark beetles bore vertical tunnels in the cambium where they lay their eggs. The larvae feed on the cambium and bore horizontal tunnels through it. Eventually the tunnels girdle the tree, cutting off the water supply. 1,000 bark beetles are enough to kill a fully grown tree In just 8 weeks. The larvae they lay in the tunnels hatch to produce  up to 50,000 new beetles to attack neighboring trees.

 

Kiener says the destruction of the forest began with a massive windfall caused by a storm. The storm weakened the root systems of the trees, so that they no longer had an optimal water supply. Weakened trees attract bark beetles through the release of a special scent. When the adult beetle bores through the bark it releases its own scent or pheromone which in turn attracts other beetles.

 

“Two years after the storm, we realized that trees were dying at the edge of the windfall,” explains Kiener. “That was a sign Bark beetles had started their destruction and were going to attack more trees in the area. There were five or six years when the bark beetle population was growing to a peak, affecting a lot of spruce trees and killing them. Then there was a decrease, and after another 5 or 6 years the attack was over. In the beginning of the 90s we had another big storm and big windfall and that was the signal for the second bark beetle mass propagation.”

 

The Bavarian Forest National Park is the largest forest area in central Europe where nothing has been done to interfere with nature and to stop the bark beetle attack. The forest has been simply left to its own devices. Dead wood is not removed and nothing is done to prevent pests like the bark beetle from massive destruction. The park consists of two different forest ecosystems. In the high elevations and wet bottom areas  there is natural spruce forest. In between is mixed mountain forest. Kiener says the damaged areas in both ecosystems are now slowly regenerating.

 

“In the more temperate areas we have mixed mountain forest with spruce with silver fir, red beech. In this mountainous area the new tree generation is fantastically mixed – more broadleaf trees than before,” says Kiener.  “After every bark beetle attack,  you have winners and losers. The three-toed woodpecker is a bird that is specialized in eating the spruce bark beetle.   the During the attack, the wood pecker population grew along with the growing population of the bark beetle. When the trees were dead and the beetles left, the food basis of the wood  pecker was also gone and they also moved on to other areas.”

 

The Bavarian Forest lies along the Czech border. For centuries the area in southern Germany depended on the forest economically. Generations of local inhabitants made their living by working in the forest and many local farmers had forestry rights. Now only four farmers remain who have an ancestral right to cut lumber. Five farmers still retain their ancestral rights to gather firewood. Since the area was declared a national park in 1970, park officials have gradually bought out such rights or replaced them by supplying farmers with commercial lumber.

 

In 1981 the Bavarian Forest National Park was named a Unesco Biosphere as well. Joseph Wanninger is charge of the biosphere project. He says the inhabitants, for whom the forest represented an important asset in terms of natural resources in the past and as a tourist attraction in the present, were at first appalled that officials did not intervene to stop bark-beetle damage.

 

“In the beginning there were many problems. The people here wanted us to change the National Park concept to allow us to  stop the bark beetle – to come into the forest with power saws and machines and to fight the beetle. Then it became clear to them that such action would result in huge bare areas. The national park is important to the tourist industry and a forest without trees would be bad for tourism. I guess they thought that dead trees are better than no trees. Now, although they are still very critical, they accept that we do not intervene and let nature take its course.”

 

Across the border lies the Sumova National Park of the Czech Republic. With 70 thousand hectares the Czech forest is nearly three times the size of the Bavarian forest. There the forestry officials have been fighting the bark beetle. The only effective way to stop destruction is to fell the infested tree and remove it form the park. In hard to access areas, the tree is felled, the bark removed and destroyed. The wood is left to rot. Bavarian Forest park officials follow the same procedure in the buffer zones between wilderness areas and commercial forests, in order to prevent the bark beetle from spreading outside the confines of the park.

 

With the entry of the  Czech Republic into the European Union, Wanninger hopes that the first steps can be taken to expand the Bavarian Forest Biosphere across the border into the Czech republic – creating one of the world’s first trans-border Unesco biospheres. “The goal is one biosphere that crosses the border and includes both parks,” says Wanninger. “With their entry  into the EU, we hope the cooperation will be easier and I am sure we will begin work on an expanded cross border biosphere.”

 

Such a biosphere would include nearly 100,000 hectares of forest. For the wild animals inhabiting the Park, borders were never a hindrance. There are signs of wolves coming into Bavaria from the Sumova. Bears, which no longer exist in the wild in the Bavarian forest are also still found across the border. One species that is again found in the park is the Lynx, which has resettled remoter areas of the forest.

Birds, nearly extinct half a century ago have also returned. On his almost daily inspection tours of the park Hans Kiener has spotted the illusive caiperceille.

 

“One of the most famous birds of this area is the caiperceille,” says Kiener. “It is a large wood grouse. It was the most desired hunting bird in this area for centuries.  Around 1950 hunting was banned because the bird had become so rare we feared it would become extinct. When the bark beetle attacked the forest there was a fear the last of the caiperceilles would die, but we see that the birds have resettled an area of the forest where the bark beetle had killed the trees about ten years ago. We are very keen to see how this will go on.”

 

It will take another generation before the forest recovers. It can take 40 years for a spruce to become the size of a Christmas tree. Most of the destroyed trees were  between 60 and 400 years old. The bark beetle attacks are receding, but the last 20 years have shown that the bark beetle population is cyclical, with its own peaks and valleys. Currently beetle damage in the Bavarian forest is at a low point and destruction, while it still goes on, has substantially slowed down. Forest officials hope the worst is over and that they can concentrate on protecting the forest while it regenerates. The rotting wood of the dead trees provides an ideal nursery for the new trees. They slowly release their nutrients into the ground and allow the sun to filter through to the young seedlings that will make up the natural forest of the future. 

 

 © Mariana Schroeder, 2003