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Mountain forests are plant diversity hotspots, but changing climate and increasing forest disturbances will likely lead to far‐reaching plant community change. Projecting future change, however, is challenging for forest understory plants, which respond to forest structure and composition as well as climate. Here, we jointly assessed the effects of both climate and forest change, including wind and bark beetle disturbances, using the process‐based simulation model iLand in a protected landscape in the northern Alps (Berchtesgaden National Park, Germany), asking: (1) How do understory plant communities respond to 21st‐century change in a topographically complex mountain landscape, representing a hotspot of plant species richness? (2) How important are climatic changes (i.e., direct climate effects) versus forest structure and composition changes (i.e., indirect climate effects and recovery from past land use) in driving understory responses at landscape scales? Stacked individual species distribution models fit with climate, forest, and soil predictors (248 species currently present in the landscape, derived from 150 field plots stratified by elevation and forest development, overall area under the receiving operator characteristic curve = 0.86) were driven with projected climate (RCP4.5 and RCP8.5) and modeled forest variables to predict plant community change. Nearly all species persisted in the landscape in 2050, but on average 8% of the species pool was lost by the end of the century. By 2100, landscape mean species richness and understory cover declined (−13% and −8%, respectively), warm‐adapted species increasingly dominated plant communities (i.e., thermophilization, +12%), and plot‐level turnover was high (62%). Subalpine forests experienced the greatest richness declines (−16%), most thermophilization (+17%), and highest turnover (67%), resulting in plant community homogenization across elevation zones. Climate rather than forest change was the dominant driver of understory responses. The magnitude of unabated 21st‐century change is likely to erode plant diversity in a species richness hotspot, calling for stronger conservation and climate mitigation efforts. [ABSTRACT FROM AUTHOR]

The National Climate Initiative (NKI) in Germany provides a strong incentive for local governments to apply for funding to engage in climate protection activities. Yet, the latest evaluation of the NKI confirms that there is a great disparity in the distribution of funding across regions. Taking this regional fragmentation as a starting point, we ask the following: How can we explain disparity in the amount of funding across counties and cities? We draw on climate policy literature pointing to the role of socioeconomic and political determinants and the settlement structure to answer this question. We study all 400 cities and counties to test hypotheses concerning disparity in the likelihood and amount of climate funding, using data from the German Ministry for the Environment and further regional statistics. Running different multilevel regression models, we show that local climate funding is more likely in cities and more urbanized counties than in rural counties with less population and oftentimes also with less young and educated people. We argue that despite the increasing number of local governments getting active in climate protection in Germany, there is important unused potential for climate change mitigation in rural counties. Therefore, we conclude by proposing a new research agenda focusing on climate change mitigation in rural areas. [ABSTRACT FROM AUTHOR]

Coastal salt marshes have an important role in climate change adaptation and mitigation. Direct and indirect responses to warming are expected to vary along the marsh elevation gradient, making ecosystem responses to warming at this marine‐terrestrial ecotone uncertain. The Marsh Ecosystem Response to Increased Temperatures (MERIT) experiment was established in 2018 on the North Sea coast of Germany. Experimental plots are evenly distributed over three elevational marsh zones (pioneer, low marsh, and high marsh) and include three temperature treatments (ambient, +1.5°C, +3.0°C). MERIT's novel design combines active warming (horizontal surface warming cables and vertical soil warming pins) with passive, partially covered domes. For performance assessment, temperature deltas between ambient and warmed plots were calculated and evaluated at seasonal, daily, and diurnal timescales. We used Linear Mixed Models with Residual Maximum Likelihood for evaluating warming treatment effects and constraining environmental factors. MERIT was effective at ecosystem warming in this high‐energy environment both above‐ and belowground. Mixed models show that warming treatment dominates temperature differences belowground and at the soil surface, along with factors such as wind speed, flooding duration, and solar radiation. Aboveground warming was lower than belowground warming, but the dome design minimized issues seen in other open‐top chamber experiments. The combination of passive aboveground warming with feedback‐controlled active surface and belowground heating provides a setup for understanding warming effects on tidal ecosystems without altering the natural impacts of wind, radiation, and tidal inundations at high‐energy coastlines. Our design creates opportunities to expand future warming experiments to remote locations and technically challenging environments. Plain Language Summary: Coastal vegetated ecosystems such as salt marshes have been highlighted for their important role in climate change adaptation and mitigation, especially in storing carbon. However, responses of ecosystem functioning and biogeochemistry to warming are largely unknown and expected to differ based on hydrology. The Marsh Ecosystem Response to Increased Temperatures (MERIT) experiment was established in 2018 in a Wadden Sea salt marsh and spans the entire salt marsh elevation gradient with pioneer, low marsh, and high marsh vegetation communities. Our objective is to create a novel ecosystem warming design that can be used in coastal wetland ecosystems prone to tidal flooding and wave disturbance. The MERIT experiment is effective at warming this dynamic ecosystem. Mixed models show the warming treatment factor dominates temperature differences belowground and at the soil surface. Aboveground performance was lower than that of the belowground treatments but better than previous experiments. Performance increased with decreasing wind speed and increased solar radiation. Our study improves understanding between biological systems and global warming. This novel experiment allows us to directly quantify ecosystem response to warming, while allowing for tidal inundation to continue. Key Points: Marsh Ecosystem Response to Increased Temperatures (MERIT) is a novel ecosystem warming experiment in a high‐energy coastal salt marshMERIT achieves passive aboveground and active belowground warming to 1 m soil depthMERIT tests warming effects on ecosystem functioning along a marine‐terrestrial ecotone [ABSTRACT FROM AUTHOR]

Proliferative kidney disease (PKD) caused by the myxozoan parasite Tetracapsuloides bryosalmonae is an emerging salmonid disease implicated in recent declines in salmonid populations. Laboratory experiments have shown that the clinical symptoms of PKD exacerbate with increasing temperature. However, empirical evidence for a relationship between climate change and PKD driven declines in wild salmonid stocks is scarce.The current study uses both empirical data and ecological niche modelling to extrapolate future changes in temperature and precipitation on the spread of PKD in relation to changes in suitability of rivers for its primary bryozoan and secondary salmonid hosts.A 20‐year dataset on brown trout density using standardised method shows a decline of more than 50% in the population of the river Wutach, south‐western Germany at 536–755 m elevation. The decline coincides with higher prevalence of PKD. This decline was temperature related and driven by reduced local survival of parr to yearlings. Kidney hyperplasia was highest at low elevations and correlated negatively with trout density.Niche models based on state‐wide data show strong overlap in the areas suitable for T. bryosalmonae and its primary bryozoan hosts, and a strong link with temperature. Projections based on moderate to high emission‐case climate change scenarios predict a 50%–82% decrease in the area suitable for salmonids within this century, linked to PKD.The empirical data identify temperature‐mediated PKD as the underlying cause of the population decline. This relationship was corroborated by the niche modelling results. The highest losses are expected in projected salmonid suitable areas where salmonid habitats currently overlap with areas suitable for T. bryosalmonae.With ongoing climate change, both current and future populations are at severe risk to T. bryosalmonae and its associated disease PKD. Conservation efforts of salmonid stocks are dependent on climate mitigation and measures to help salmonids adapt to the disease. [ABSTRACT FROM AUTHOR]

Germany's greenhouse gas emissions have declined by 35% since 1990, and the national policy ambition is to become largely carbon‐neutral by 2050. A change of the industrial landscape and a partial transformation of energy supply have contributed to reductions so far, but for deep reductions, a deep transformation of the country's industrial metabolism is needed. While energy efficiency is well established, the same cannot be said for material efficiency, which includes product light‐weighting, lifetime extension, more intense use, and value retention strategies like higher recycling rates, remanufacturing, and reuse. Sector‐specific research showed substantial energy and emissions savings potentials of material efficiency, but the overall material efficiency potential for most world economies, including Germany, is unknown. We applied an open‐source and modular dynamic material flow analysis model of the transformation of passenger vehicles, residential buildings, and commercial and service buildings in Germany (together ca. 50% of national greenhouse gases) to a material‐efficient system, covering the time span 2016–2060. The potential impact of the above‐mentioned material efficiency strategies was studied for the climate‐relevant materials concrete, steel, timber, aluminum, and plastics. Once the potentials of energy‐efficient products, electrification of end‐use sectors, and energy system transformation are seized, supply and demand side material efficiency and sufficiency can reduce remaining 2050 emissions by an additional 19–34 % (passenger vehicles), 27–31% (residential buildings), and 14–19% (non‐residential buildings). The 2016–2050 cumulative savings can be up to 750 Mt (million metric tons) CO2‐eq. Material efficiency can be a key contributor to deep emissions cuts like a 95% target. This article met the requirements for a gold‐gold JIE data openness badge described at http://jie.click/badges. [ABSTRACT FROM AUTHOR]

Crop residue exploitation for bioenergy can play an important role in climate change mitigation without jeopardizing food security, but it may be constrained by impacts on soil organic carbon (SOC) stocks, and market, logistic and conversion challenges. We explore opportunities to increase bioenergy potentials from residues while reducing environmental impacts, in line with sustainable intensification. Using the case study of North Rhine‐Westphalia in Germany, we employ a spatiotemporally explicit approach combined with stakeholder interviews. First, the interviews identify agronomic and environmental impacts due to the potential reduction in SOC as the most critical challenge associated with enhanced crop residue exploitation. Market and technological challenges and competition with other residue uses are also identified as significant barriers. Second, with the use of agroecosystem modelling and estimations of bioenergy potentials and greenhouse gas emissions till mid‐century, we evaluate the ability of agricultural management to tackle the identified agronomic and environmental challenges. Integrated site‐specific management based on (a) humus balancing, (b) optimized fertilization and (c) winter soil cover performs better than our reference scenario with respect to all investigated variables. At the regional level, we estimate (a) a 5% increase in technical residue potentials and displaced emissions from substituting fossil fuels by bioethanol, (b) an 8% decrease in SOC losses and associated emissions, (c) an 18% decrease in nitrous oxide emissions, (d) a 37% decrease in mineral fertilizer requirements and emissions from their production and (e) a 16% decrease in nitrate leaching. Results are spatially variable and, despite improvements induced by management, limited amounts of crop residues are exploitable for bioenergy in areas prone to SOC decline. In order to sustainably intensify crop residue exploitation for bioenergy and reconcile climate change mitigation with other sustainability objectives, such as those on soil and water quality, residue management needs to be designed in an integrated and site‐specific manner. [ABSTRACT FROM AUTHOR]

In order to examine the impact of different Power‐to‐X technologies on the transformation of the German energy system and meeting the climate change mitigation goals, a cross‐sectoral energy system model was developed. The results show that Power‐to‐X will be essential for a successful energy transition. Especially in applications where high energy densities are required and only few other options for defossilization exist, Power‐to‐X technologies become essential. [ABSTRACT FROM AUTHOR]

This stated preferences survey determines the willingness to pay ( WTP) for climate change mitigation policies using a representative sample of the German population. WTP is compared across three valuation question formats in a split sample design: the dichotomous choice ( DC) referendum, the dissonance minimizing ( DM) referendum and the two-way payment ladder ( TWPL). The influence of multinational cooperation on WTP is assessed by variation in the hypothetical scenarios. We demonstrate that the DM referendum and the TWPL, two question formats that induce similar response incentives, yield equal mean WTPs. Multinational cooperation did not change WTP in any of the question formats. Implications for current contingent valuation practice are discussed. [ABSTRACT FROM AUTHOR]

This article revisits a number of familiar debates about climate change mitigation yet draws some unorthodox conclusions. First, that progress towards a renewable small-scale energy future in environmentally conscious countries such as Germany and Sweden may take the world as a whole further away from climate stability by reducing the political pressure to finance breakthrough innovation. Second, that without such game-changing innovations, developing countries will continue to deploy whatever technologies are domestically available, scalable and affordable, including thermal coal power in most instances. Third and finally, that as any realistic hope of achieving climate stability hinges on the innovation of breakthrough technologies, the urgency of climate change calls not so much for the domestic deployment of existing energy technologies but rather a concentrated effort to develop technologies that will be adopted globally. These arguments imply that national innovation policy, and an international treaty establishing a 'Low-Emissions Technology Commitment' should be the central focus of climate policy. [ABSTRACT FROM AUTHOR]

Germany and Great Britain together emit one third of all EU emissions. Achieving the overall EU targets will thus require a transformation particularly in these two countries. There is no effective climate protection without addressing the biggest emitters. [ABSTRACT FROM AUTHOR]

Over the last 15 years, research on carbon lock‐in has investigated why decarbonization evolves so slowly in Western industrialized countries. In this paper, we argue that the role of discourses has been overlooked in the literature on carbon lock‐in. We argue that discourses are both part of lock‐in mechanisms and, using the concept of discursive turning points, important factors in explaining change. This implies that we need to carefully investigate the dominant discourses that constitute and justify the very technologies, institutions and behaviors of the status quo. For the case of the German energy transition, we demonstrate the importance of discursive turning points for overcoming carbon lock‐in, based on a literature review. Germany's long‐standing lock‐in of fossil fuels and nuclear power was undermined by the rise of the energy transition discourse. This discourse transitioned from a very marginal position to dominance through a number of factors, winning against the energy mix discourse. Over time the energy transition discourse became de‐radicalized. Coal has been able to defend its role in the German energy mix in the name of affordability and energy security. While renewables continue to grow, this happens alongside a remaining carbon lock‐in. We conclude that discursive lock‐in and discursive turning points are useful analytical tools that help to explain how the transition to renewable energies unfolds. In future research, the interaction between discursive lock‐ins and other types of lock‐in should be investigated. This article is categorized under:The Carbon Economy and Climate Mitigation > Decarbonizing Energy and/or Reducing DemandPolicy and Governance > Governing Climate Change in Communities, Cities, and Regions Discursive turning points in the German energy transition. [ABSTRACT FROM AUTHOR]