KEY POINTS:
Beech forest in the Nelson Lakes National Park is recovering well after being stripped of its canopy by hungry caterpillars, says the Department of Conservation.
Foliage in D'Urville Valley started thinning in September, and this spread to neighbouring valleys in the following months, said DoC biodiversity manager Brian Paton. Thousands of hectares of forest were affected by the canopy dieback, a result of an unusual surge in the number of beech-eating caterpillars from the Thiotricha moth.
But the large tracts of bare, dead-looking red and silver beech trees are now regaining much of their foliage, Mr Paton said. Although a small number of trees had died, a warm autumn with few frosts had helped most of them to recover well.
He said DoC wasn't certain of the reason for the caterpillar explosion.
"It may have been triggered by climatic conditions in winter and spring last year which allowed a large number of moth eggs to survive."
Mr Paton said large-scale damage to trees from surges of certain insects was a natural phenomenon that happened occasionally and forests usually recovered.
- NZPA
