Poleward movement seen in many species
By Summit Voice
FRISCO — Researchers in Finland say they’ve documented bird populations trends that are at least partly linked with global warming. Comparing data from extensive bird counts conducted between 1981 to 1999, and 2000 to 2009, the biologists said that, in general, northern species have decreased and southern species increased.
Mean temperatures in Finland rose between the two periods, with April to June mean temperatures climbing by 0.7 degrees Celsius.
According to the study, population densities of common forest habitat generalists remained the same between the two periods, while densities of species of conservation concern showed contrasting trends. Species preferring old-growth or mature forests increased, but those living on mires and wetlands, and species of Arctic mountains decreased.
The trends suggest that climate change impacts on species in natural boreal and Arctic habitats most probably are habitat-specific with large differences in response times and susceptibility. Open mires and mountain heaths change more rapidly in consequence of climate warming than old-growth forests, for which reason populations on mires and mountain heaths may also be more affected by climate change.
“These trends are most probably connected with climate change, but sucessional changes in protected areas and regional habitat alteration should also be taken into account,” said Dr. Virkkala, the leading author of the study. Of species preferring old-growth or mature forests, a larger proportion are southern than among species of mires and wetlands, or of Arctic mountains, most or all of which, respectively, had a northerly distribution.
The research should help inform management of protected areas, the researchers said, explaining that changes in species ranges driven by global warming pose a challenge to resource managers.
The study “Preserving species populations in the boreal zone in a changing climate: contrasting trends of bird species groups in a protected area network” by Raimo Virkkala from the Finnish Environment Institute and Ari Rajasärkkä from Metsähallitus was published in the open access journal Nature Conservation. Bird censuses were compiled and organized by Metsähallitus, which governs the stated-owned protected areas in Finland. Tens of competent ornithologists carried out the censuses, which included altogether over 11,600 km of line transects.