• Energy Research

Anthropogenic changes to the environment are leading to a decrease in global biodiversity, with the aquatic insect fauna being particularly affected. Information on insect loss trends is mainly based on decadal-scale monitoring data, which does not allow natural baselines to be established, or for the impacts of multiple anthropogenic drivers to be separated. Here, we present decadal- and centennial-scale datasets of chironomid diversity change and quantitatively compare changes in chironomid diversity resulting from climate change and anthropogenic impacts. Our decadal-scale data shows changes in community composition for a set of lakes near Bergen (Norway) between 1996 and 2019, but trends in diversity change were not unidirectional across the twenty study sites. We additionally analysed temporal trends in chironomid communities in sediment records obtained from two of the study sites in order to provide a centennial-scale perspective to the observed recent changes. The sediment records date back to ca. 800 CE, and on these longer timescales the effects of climate on insect diversity are clearly identifiable and quantifiable. By using a palaeoecological approach, we show that the decadal-scale data did not capture the full extent of human-induced insect dynamics in this region. We conclude that palaeoecological records contribute unique insights on baseline conditions, effects of individual drivers, and long-term diversity trends. Such information is key for effective ecosystem restoration and insect conservation.

AbstractAnthropogenic climate change is predicted to severely impact the global hydrological cycle1, particularly in tropical regions where agriculture-based economies depend on monsoon rainfall2. In the Horn of Africa, more frequent drought conditions in recent decades3,4 contrast with climate models projecting precipitation to increase with rising temperature5. Here we use organic geochemical climate-proxy data from the sediment record of Lake Chala (Kenya and Tanzania) to probe the stability of the link between hydroclimate and temperature over approximately the past 75,000 years, hence encompassing a sufficiently wide range of temperatures to test the ‘dry gets drier, wet gets wetter’ paradigm6 of anthropogenic climate change in the time domain. We show that the positive relationship between effective moisture and temperature in easternmost Africa during the cooler last glacial period shifted to negative around the onset of the Holocene 11,700 years ago, when the atmospheric carbon dioxide concentration exceeded 250 parts per million and mean annual temperature approached modern-day values. Thus, at that time, the budget between monsoonal precipitation and continental evaporation7 crossed a tipping point such that the positive influence of temperature on evaporation became greater than its positive influence on precipitation. Our results imply that under continued anthropogenic warming, the Horn of Africa will probably experience further drying, and they highlight the need for improved simulation of both dynamic and thermodynamic processes in the tropical hydrological cycle.

Marked changes in human dispersal and development during the Middle to Upper Paleolithic transition have been attributed to massive volcanic eruption and/or severe climatic deterioration. We test this concept using records of volcanic ash layers of the Campanian Ignimbrite eruption dated to ca. 40,000 y ago (40 ka B.P.). The distribution of the Campanian Ignimbrite has been enhanced by the discovery of cryptotephra deposits (volcanic ash layers that are not visible to the naked eye) in archaeological cave sequences. They enable us to synchronize archaeological and paleoclimatic records through the period of transition from Neanderthal to the earliest anatomically modern human populations in Europe. Our results confirm that the combined effects of a major volcanic eruption and severe climatic cooling failed to have lasting impacts on Neanderthals or early modern humans in Europe. We infer that modern humans proved a greater competitive threat to indigenous populations than natural disasters.

The INTIMATE protocol for the correlation of marine ice core and terrestrial records is here updated, reflecting recent developments in palaeoclimate research. Originally focussed on Last Glacial to Interglacial Transition (LGIT: 22,000–11,500 years B.P.), the INTIMATE group has now extended its study period back to 60,000 years. As a first step, the INTIMATE event stratigraphy has now been extended to include 8000–48,000 b2k based on a combined NGRIP and GRIP isotope profile against a GICC05 chronology and key tephra horizons from Iceland and continental European volcanic sources. In this lead article of this INTIMATE special issue we introduce some of the recent achievements of the INTIMATE community and discuss the challenges associated with extending the INTIMATE approach back in time, focussing in particular on the chronological problems inherent in comparing different proxy records. The INTIMATE approach has thus far been limited predominantly to the North Atlantic and Australasian regions and we also discuss the potential to extend the INTIMATE protocol beyond these regions.

This dataset provides chironomid count data for core tops from 20 lakes located near Bergen, Norway. The lakes are situated either in the Røldal region or in the Førde region. For each lake, the chironomid counts as well as the coordinates (latitude/longitude) are presented. We obtained samples from the centre of each lake using a HON/Kajak gravity corer and analysed the top-centimetre (0-1 cm sediment depth) to determine the composition of the chironomid fauna. All sediment samples were retrieved during fieldwork in August and September 2019. Samples were transported to the laboratory (Birkbeck University of London, UK), where they were weighted and processed using standard protocols – this involved 20 min treatment with warm KOH (10 %) and sieving over a 100 µm mesh. Chironomid head capsules were subsequently handpicked from the residue, mounted on permanent microscope slides, and identified using Brooks et al. (2007). This dataset provides chironomid count data in number of chironomid head capsules per sample. Through a comparison against data from 1996 (Brooks & Birks, 2001), the chironomid dataset provides insight in the recent changes in the insect community of the lake ecosystem under ongoing climate change.

This dataset provides chironomid count data and loss-on-ignition measurements for a short sediment record from lake Lontjørnane, located in the Røldal region, Norway. The core spans 33cm and dates from ca 1175 CE to the present. We obtained a sediment core from the centre of the lake (8.8 m water depth) using a HON/Kajak gravity corer during fieldwork in September 2019, and subdivided the core into 1-cm-thick samples in the field. Samples were transported to the laboratory (Birkbeck University of London, UK), where they were weighted and processed using standard protocols – this involved 20 min treatment with warm KOH (10 %) and sieving over a 100 µm mesh. Chironomid head capsules were subsequently handpicked from the residue, mounted on permanent microscope slides, and identified using Brooks et al. (2007). This dataset provides chironomid count data in number of chironomid head capsules per sample. Additionally, loss-on-ignition was determined for each sample by comparing the dry weight of the sample before and after combustion at 550 °C following Heiri et al. (2001). The chironomid dataset provides insight in centennial-scale changes in the insect community of the lake ecosystem under past climate change and current anthropogenic impact.