Finnish atlas range margins of southern birds moved north more slowly in 2006-10 to 2022-25 than before while isotherms moved fast; lower detection in 2022-25 explains part of this
We used the new fourth Finnish breeding bird atlas (2022-25) to test whether the range shifts seen in the 1974-79, 1986-89 and 2006-10 atlases continued. We wrote the plan before we downloaded the atlas-4 species data. We used 10 km squares that had at least satisfactory survey activity in both atlases of each pair. The northern margins of 70 southern species moved north by 0.49 km per year from 2006-10 to 2022-25 (95% CI -0.68 to 1.66), against 4.99 km per year from 1986-89 to 2006-10 and 3.48 km per year from 1974-79 to 2006-10. In the same interval, the May-June isotherm moved about 9 km per year. The southern margins of 13 northern species moved north by 5.26 km per year (2.20 to 8.64), against about 1.2 km per year before. Species rates did not repeat between intervals (Spearman 0.01), and extrapolation of earlier species rates forecast the 2022-25 margins worse than no change (+21.8 km mean absolute error). Atlas 4 recorded about 5 fewer species per well-surveyed square, and the activity categories did not remove this difference. When we balanced detection with 136 widespread species, the leading edge moved 1.29 km per year (0.04 to 2.62) against 2.83 km per year before. When atlas 4 detected at least as many widespread species, it moved 3.58 km per year. Thus a slowdown remains under balanced detection, but its size depends on the detection control. The calibrator analyses were not in the plan. The numbers of northern species are small, and the bootstrap does not include spatial correlation.
References
5- reviewsdoi:10.1371/journal.pone.0043648
- useshttps://lintuatlas.fi/
- useshttps://info.laji.fi/etusivu/kansalaistiede/lintuatlas/
- usesdoi:10.1029/2017JD028200
- Northern range margins of southerly British invertebrates moved north again from 2001-10 to 2015-24 in GBIF hectad data; the rate depends on effort control, and species rates did not repeat
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