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Biological responses to climate change have been widely documented across taxa and regions, but it remains unclear whether species are maintaining a good match between phenotype and environment, i.e. whether observed trait changes are adaptive. Here we reviewed 10,090 abstracts and extracted data from 71 studies reported in 58 relevant publications, to assess quantitatively whether phenotypic trait changes associated with climate change are adaptive in animals. A meta-analysis focussing on birds, the taxon best represented in our dataset, suggests that global warming has not systematically affected morphological traits, but has advanced phenological traits. We demonstrate that these advances are adaptive for some species, but imperfect as evidenced by the observed consistent selection for earlier timing. Application of a theoretical model indicates that the evolutionary load imposed by incomplete adaptive responses to ongoing climate change may already be threatening the persistence of species. It is unclear whether species’ responses to climate change tend to be adaptive or sufficient to keep up with climate change. Here, Radchuk et al. perform a meta-analysis showing that in birds phenology has advanced adaptively in some species, though not all the way to the new optima.

Methylmercury (MeHg) is a potent neurotoxin that biomagnifies in marine food webs. Inorganicmercury (Hg) methylation is conducted by heterotrophic bacteria inhabiting sedimentor settling detritus, but endogenous methylation by the gut microbiome of animals in thelower food webs is another possible source. We examined the occurrence of the bacterialgene (hgcA), required for Hg methylation, in the guts of dominant zooplankters in the NorthernBaltic Sea. A qPCR assay targeting the hgcA sequence in three main clades (Deltaproteobacteria,Firmicutes and Archaea) was used in the field-collected specimens ofcopepods (Acartia bifilosa, Eurytemora affinis, Pseudocalanus acuspes and Limnocalanusmacrurus) and cladocerans (Bosmina coregoni maritima and Cercopagis pengoi). All copepodswere found to carry hgcA genes in their gut microbiome, whereas no amplification wasrecorded in the cladocerans. In the copepods, hgcA genes belonging to only Deltaproteobacteriaand Firmicutes were detected. These findings suggest a possibility that endogenousHg methylation occurs in zooplankton and may contribute to seasonal, spatial andvertical MeHg variability in the water column and food webs. Additional molecular and metagenomicsstudies are needed to identify bacteria carrying hgcA genes and improve theirquantification in microbiota.

Based on the Baltic Earth Assessment Reports of this thematic issue in Earth System Dynamics and recent peer-reviewed literature, current knowledge of the effects of global warming on past and future changes in climate of the Baltic Sea region is summarised and assessed. The study is an update of the Second Assessment of Climate Change (BACC II) published in 2015 and focuses on the atmosphere, land, cryosphere, ocean, sediments, and the terrestrial and marine biosphere. Based on the summaries of the recent knowledge gained in palaeo-, historical, and future regional climate research, we find that the main conclusions from earlier assessments still remain valid. However, new long-term, homogenous observational records, for example, for Scandinavian glacier inventories, sea-level-driven saltwater inflows, so-called Major Baltic Inflows, and phytoplankton species distribution, and new scenario simulations with improved models, for example, for glaciers, lake ice, and marine food web, have become available. In many cases, uncertainties can now be better estimated than before because more models were included in the ensembles, especially for the Baltic Sea. With the help of coupled models, feedbacks between several components of the Earth system have been studied, and multiple driver studies were performed, e.g. projections of the food web that include fisheries, eutrophication, and climate change. New datasets and projections have led to a revised understanding of changes in some variables such as salinity. Furthermore, it has become evident that natural variability, in particular for the ocean on multidecadal timescales, is greater than previously estimated, challenging our ability to detect observed and projected changes in climate. In this context, the first palaeoclimate simulations regionalised for the Baltic Sea region are instructive. Hence, estimated uncertainties for the projections of many variables increased. In addition to the well-known influence of the North Atlantic Oscillation, it was found that also other low-frequency modes of internal variability, such as the Atlantic Multidecadal Variability, have profound effects on the climate of the Baltic Sea region. Challenges were also identified, such as the systematic discrepancy between future cloudiness trends in global and regional models and the difficulty of confidently attributing large observed changes in marine ecosystems to climate change. Finally, we compare our results with other coastal sea assessments, such as the North Sea Region Climate Change Assessment (NOSCCA), and find that the effects of climate change on the Baltic Sea differ from those on the North Sea, since Baltic Sea oceanography and ecosystems are very different from other coastal seas such as the North Sea. While the North Sea dynamics are dominated by tides, the Baltic Sea is characterised by brackish water, a perennial vertical stratification in the southern subbasins, and a seasonal sea ice cover in the northern subbasins.

Although ecometric methods have been used to analyse fossil mammal faunas and environments of Eurasia and North America, such methods have not yet been applied to the rich fossil mammal record of eastern Africa. Here we report results from analysis of a combined dataset spanning east and west Turkana from Kenya between 7 and 1 million years ago (Ma). We provide temporally and spatially resolved estimates of temperature and precipitation and discuss their relationship to patterns of faunal change, and propose a new hypothesis to explain the lack of a temperature trend. We suggest that the regionally arid Turkana Basin may between 4 and 2 Ma have acted as a ‘species factory’, generating ecological adaptations in advance of the global trend. We show a persistent difference between the eastern and western sides of the Turkana Basin and suggest that the wetlands of the shallow eastern side could have provided additional humidity to the terrestrial ecosystems. Pending further research, a transient episode of faunal change centred at the time of the KBS Member (1.87–1.53 Ma), may be equally plausibly attributed to climate change or to a top-down ecological cascade initiated by the entry of technologically sophisticated humans. This article is part of the themed issue ‘Major transitions in human evolution’.

Birds of prey, owls and falcons are widely used as sentinel species in raptor biomonitoring programmes. A major current challenge is to facilitate large-scale biomonitoring by coordinating contaminant monitoring activities and by building capacity across countries. This requires sharing, dissemination and adoption of best practices addressed by the Networking Programme Research and Monitoring for and with Raptors in Europe (EURAPMON) and now being advanced by the ongoing international COST Action European Raptor Biomonitoring Facility. The present perspective introduces a schematic sampling protocol for contaminant monitoring in raptors. We provide guidance on sample collection with a view to increasing sampling capacity across countries, ensuring appropriate quality of samples and facilitating harmonization of procedures to maximize the reliability, comparability and interoperability of data. The here presented protocol can be used by professionals and volunteers as a standard guide to ensure harmonised sampling methods for contaminant monitoring in raptors.

We present evidence that the abundance of harbour seals in the Kattegat-Skagerrak is in decline. Until recently, the Kattegat-Skagerrak harbour seal population has grown exponentially as it has recovered from historic over-hunting and two mass mortality events. This has provided an important case study for the influence of environmental factors on population growth. Over recent years, deteriorating average body condition and reduced pup counts in certain colonies have indicated that the population is under stress. At the same time, there has been an increase in hunting in the region which may compound existing environmental stressors. To determine trends in harbour seal abundance, we compile aerial survey data for the Kattegat-Skagerrak and South-Western Baltic Sea (S.W. Baltic) populations between the years 2003 and 2023. With parametric modelling, we find that a logistic growth model is the best fit for aerial survey data from the Kattegat-Skagerrak population, while an exponential growth model is the best fit for data from the smaller S.W. Baltic population. We determine trends by fitting non-parametric Generalised Additive Models (GAMs) to aerial survey data and calculating their first derivative. In the Kattegat-Skagerrak, we estimate an annual decline of – 408 individuals (SE = 242, CI 95% = [- 882, 67]) at the end of the survey period. This decline represents approximately 3.3% of the estimated mean count in 2023. Rate of change remained positive in the separate S.W. Baltic population throughout the survey period at an estimated annual increase of 54 individuals (SE = 23, CI 95% = [9,99]), representing approximately 3.9% of mean counts in 2023. We find that the final rate of change was zero or below zero in eleven out of twelve subregions (representing individual colonies) in the Kattegat-Skagerrak. Declining counts in the Kattegat-Skagerrak since the mid-2010s may be influenced by changes in haul-out behaviour as a result of increased population density or vessel traffic. Despite this, declines likely reflect real changes in seal abundance. Changes in abundance may be the result of well documented environmental degradation affecting prey availability and causing regionally lowered birth rates.

Enhancing the role of the soil microbiota in plant phosphorus (P) and sulfur (S) supply through application of organic fertilizer could reduce dependencies on non-sustainable synthetic fertilizers. To compare the effects of organic/inorganic fertilizers on the soil microbiota, soil columns with Lolium perenne (ryegrass) were set up in a greenhouse and amended with an inorganic fertilizer, cattle slurry (organic), or urea (P- and S-free control). Ryegrass rhizosphere of the slurry treatment had significantly higher abundances of bacterial feeding nematodes, mycorrhizal colonization, cultivable heterotrophic bacteria, phosphonate- and sulfonate-utilizing bacteria, arylsulfatase activity, available P, and Variovorax asfA gene copies compared to the inorganic and urea treatments. Phosphomonoesterase activities, and gene abundances involved in organic P and S transformations (phoD, phoC, Burkholderia, and Polaromonas asfA) were similar in all treatments. Grass dry matter yield and shoot uptake of N, P, and S were significantly higher in the inorganic treatment compared to the urea and slurry treatments. Community compositions differed significantly between the three fertilizer treatments and included the bacterial, alkaline phosphomonoesterase-producing bacterial, fungal, AM fungal, and nematode communities. Bacteriodetes were found in higher relative abundance in the organic treatment, while Acidobacteria were more abundant in the urea and inorganic fertilizer treatments. These community shifts correlated significantly with grass dry matter yield, uptake of N, P, and S, mycorrhizal colonization, enzyme activities, abundances of bacteria, and bacterial feeding nematodes. We concluded that organic fertilization promoted soil microbes and nematodes which have the potential to support sustainable plant growth, provided that the overall nutrient requirements are met.