Timing migration birds
The bird species Song Thrush is changing its timing of migration in Europe, which has been observed in observations at the Polish Baltic coast over the period 1975-2014. The beginning of autumn migration at a Polish ringing station has advanced by 5 days between 1975 and 2014. The average time span of 90% of the autumn migration was extended by 5 days, probably because of early migration of young birds from first broods and late of those from second broods enabled by warm springs and summers (1). The response of Song Thrushes’ migration timing to temperatures on route and at the breeding grounds indicated high plasticity in the species and suggested it might adapt well to climate changes. Increasing numbers of Song Thrushes in Poland (2) and in Finland (3) indicate that the speciesmight indeed have benefitted from climate change in the Baltic region over the past few decades (1).
The combined impact of changing nutrient loads from land and changing climate during the 21st century for the Baltic Sea region has been assessed, for a moderate (RCP 4.5) and high-end scenario (RCP 8.5) of climate change (4). The scientists found in almost all scenario simulations, with differing nutrient inputs, reduced eutrophication and improved ecological state compared to the reference period 1976-2005. This result is a long-lasting consequence of ongoing nutrient load reductions since the 1980s. Only in case of combined high-end nutrient load and climate scenarios, eutrophication is reinforced. Effects of changing climate, within the range of considered greenhouse gas emission scenarios, are smaller than effects of considered nutrient load changes, in particular under low nutrient conditions. Hence, nutrient load reductions following the Baltic Sea Action Plan will lead to improved environmental conditions independently of future climate change (4).
The impact of excessive nutrient loads is the most important driver of hypoxia in the Baltic Sea. Without elevated nutrient concentrations, hypoxia would not have occurred during the twentieth and twenty-first centuries (5).
The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Bulgaria.
- Redlisiak et al. (2018)
- Chodkiewicz et al. (2016), in: Redlisiak et al. (2018)
- Portal of Finnish bird ringing services and bird monitoring (2017), in: Redlisiak et al. (2018)
- Saraiva et al. (2019)
- Meier et al. (2019)