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”, says Heidi Björklund who coordinated the study in the Finnish Museum of Natural History Luomus that is part of the University of Helsinki.
Hawk forests at risk of disappearing – old spruce forests should be protected
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”, confirms 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”, says leading researcher Raimo Virkkala from the Finnish Environment Institute.
The study indicates that current measures are insufficient to conserve forests valuable for biodiversity. Continuous supply of mature and old spruce forests should be secured in managed boreal landscapes. It is especially important to conserve biodiversity in privately-owned forests, as they cover most of the forests in Central Finland.
Researchers from the Finnish Museum of Natural History Luomus at the University of Helsinki, University of Jyväskylä and Finnish Environment Institute collaborated in the study. The research is part of the Finnish forest raptor project in the METSO forest biodiversity programme funded by the Ministry of the Environment, and of the IBC-Carbon project funded by the Strategic Research Council at the Academy of Finland.
Predicting valuable forest habitats using an indicator species for biodiversity
Heidi Björklund, Anssi Parkkinen, Tomi Hakkari, Risto K.Heikkinen, Raimo Virkkala, Anssi Lensu. Biological Conservation, Vol. 249, September 2020, 08682. https://doi.org/10.1016/j.biocon.2020.108682
Leading researcher, title of docent Raimo Virkkala, Finnish Environment Institute, raimo.virkkala(at)ymparisto.fi, tel. 0295 251 747
Senior Lecturer, PhD Anssi Lensu, University of Jyväskylä, anssi.lensu(at)jyu.fi, tel. 040 805 3903