Boreal forests disappear due to logging

One-tenth of the hawk forests were lost or significantly deteriorated due to logging within a span of few years, according to a study of the University of Helsinki, University of Jyväskylä and Finnish Environment Institute.

Optimal forests for the northern goshawk and associated biodiversity covered about three percent of Central Finland and were mainly located outside protected areas, said a press release of the University of Helsinki, quoting the study published recently.

Nesting forests of the goshawk often host species of conservation concern such as the Siberian flying squirrel, the three-toed woodpecker and polyporous fungi.

Many species, for example the common buzzard and honey buzzard, use old nests of goshawks for breeding. Therefore, nesting forests of the goshawk indicate hotspots of forest biodiversity.

In the study, optimal forests for the goshawk were located in Central Finland. Based on the forest structure of known nest sites, occurrences of similar forests were modelled across the study area. It appeared that the most optimal hawk forests covered only about 3 percent of Central Finland, and 96 percent of them were located completely outside protected areas. The rest of the optimal hawk forests were completely or partly within protected areas.

“Optimal hawk forests were scarce and unprotected in the landscape dominated by commercial forests”, said Heidi Björklund who coordinated the study in the Finnish Museum of Natural History Luomus that is part of the University of Helsinki.

Optimal forests for the goshawk were stout spruce forests where the timber volume of spruce exceeded 200 cubic metres per hectare. Forests were mixed with some broadleaved trees.

“According to the model developed in this study, goshawks prefer mature or old spruce forests that are at the age of regeneration felling”, said Anssi Lensu, a researcher from the University of Jyväskylä.

Logging data based on remote sensing were used to calculate the proportion of optimal hawk forests that were logged after a period of three years. Ten percent of the forests were lost or significantly deteriorated due to logging, and some logging occurred in half of the hawk forests.

The goshawk has declined based on the long-term monitoring of birds of prey at Luomus. Logging and other forest management activities have been suggested as the main reason for the decrease. This study confirms that optimal hawk forests and associated forest biodiversity of mature forest are easily lost due to logging.

“Many resident forest birds such as the willow tit and crested tit have become endangered”, said leading researcher Raimo Virkkala from the Finnish Environment Institute.