In our globalizing world, the geographical locations of food production and consumption are becoming increasingly disconnected, which increases reliance on external resources and their trade. We ...quantified to what extent water and land constraints limit countries' capacities, at present and by 2050, to produce on their own territory the crop products that they currently import from other countries. Scenarios of increased crop productivity and water use, cropland expansion (excluding areas prioritized for other uses) and population change are accounted for. We found that currently 16% of the world population use the opportunities of international trade to cover their demand for agricultural products. Population change may strongly increase the number of people depending on ex situ land and water resources up to about 5.2 billion (51% of world population) in the SRES A2r scenario. International trade will thus have to intensify if population growth is not accompanied by dietary change towards less resource-intensive products, by cropland expansion, or by productivity improvements, mainly in Africa and the Middle East. Up to 1.3 billion people may be at risk of food insecurity in 2050 in present low-income economies (mainly in Africa), if their economic development does not allow them to afford productivity increases, cropland expansion and/or imports from other countries.
Safely achieving the goals of the Paris Climate Agreement requires a worldwide transformation to carbon-neutral societies within the next 30 y. Accelerated technological progress and policy ...implementations are required to deliver emissions reductions at rates sufficiently fast to avoid crossing dangerous tipping points in the Earth’s climate system. Here,we discuss and evaluate the potential of social tipping interventions (STIs) that can activate contagious processes of rapidly spreading technologies, behaviors, social norms, and structural reorganization within their functional domains that we refer to as social tipping elements (STEs). STEs are subdomains of the planetary socioeconomic system where the required disruptive change may take place and lead to a sufficiently fast reduction in anthropogenic greenhouse gas emissions. The results are based on online expert elicitation, a subsequent expert workshop, and a literature review. The STIs that could trigger the tipping of STE subsystems include 1) removing fossil-fuel subsidies and incentivizing decentralized energy generation (STE1, energy production and storage systems), 2) building carbon-neutral cities (STE2, human settlements), 3) divesting from assets linked to fossil fuels (STE3, financial markets), 4) revealing the moral implications of fossil fuels (STE4, norms and value systems), 5) strengthening climate education and engagement (STE5, education system), and 6) disclosing information on greenhouse gas emissions (STE6, information feedbacks). Our research reveals important areas of focus for larger-scale empirical and modeling efforts to better understand the potentials of harnessing social tipping dynamics for climate change mitigation.
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Sustainable development goals (SDGs) have set the 2030 agenda to transform our world by tackling multiple challenges humankind is facing to ensure well‐being, economic prosperity, and environmental ...protection. In contrast to conventional development agendas focusing on a restricted set of dimensions, the SDGs provide a holistic and multidimensional view on development. Hence, interactions among the SDGs may cause diverging results. To analyze the SDG interactions we systematize the identification of synergies and trade‐offs using official SDG indicator data for 227 countries. A significant positive correlation between a pair of SDG indicators is classified as a synergy while a significant negative correlation is classified as a trade‐off. We rank synergies and trade‐offs between SDGs pairs on global and country scales in order to identify the most frequent SDG interactions. For a given SDG, positive correlations between indicator pairs were found to outweigh the negative ones in most countries. Among SDGs the positive and negative correlations between indicator pairs allowed for the identification of particular global patterns. SDG 1 (No poverty) has synergetic relationship with most of the other goals, whereas SDG 12 (Responsible consumption and production) is the goal most commonly associated with trade‐offs. The attainment of the SDG agenda will greatly depend on whether the identified synergies among the goals can be leveraged. In addition, the highlighted trade‐offs, which constitute obstacles in achieving the SDGs, need to be negotiated and made structurally nonobstructive by deeper changes in the current strategies.
Key Points
Synergies, defined by positive correlations between indicator pairs, outweigh trade‐offs (negative correlations) for most sustainable development goals (SDGs) and countries
SDG 1 depicts synergies with most goals while SDG 12 shows trade‐offs; SDG 3 has synergies with other SDGs in most countries and populations
For attaining the SDGs, the synergies can be leveraged and the trade‐offs need to be overcome by deeper changes in the current strategies
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We estimate the global bioenergy potential from dedicated biomass plantations in the 21st century under a range of sustainability requirements to safeguard food production, biodiversity and ...terrestrial carbon storage. We use a process‐based model of the land biosphere to simulate rainfed and irrigated biomass yields driven by data from different climate models and combine these simulations with a scenario‐based assessment of future land availability for energy crops. The resulting spatial patterns of large‐scale lignocellulosic energy crop cultivation are then investigated with regard to their impacts on land and water resources. Calculated bioenergy potentials are in the lower range of previous assessments but the combination of all biomass sources may still provide between 130 and 270 EJ yr−1 in 2050, equivalent to 15–25% of the World's future energy demand. Energy crops account for 20–60% of the total potential depending on land availability and share of irrigated area. However, a full exploitation of these potentials will further increase the pressure on natural ecosystems with a doubling of current land use change and irrigation water demand. Despite the consideration of sustainability constraints on future agricultural expansion the large‐scale cultivation of energy crops is a threat to many areas that have already been fragmented and degraded, are rich in biodiversity and provide habitat for many endangered and endemic species.
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This study quantifies, spatially explicitly and in a consistent modeling framework (Lund‐Potsdam‐Jena managed Land), the global consumption of both “blue” water (withdrawn for irrigation from rivers, ...lakes and aquifers) and “green” water (precipitation) by rainfed and irrigated agriculture and by nonagricultural terrestrial ecosystems. In addition, the individual effects of human‐induced land cover change and irrigation were quantified to assess the overall hydrological impact of global agriculture in the past century. The contributions to irrigation of nonrenewable (fossil groundwater) and nonlocal blue water (e.g., from diverted rivers) were derived from the difference between a simulation in which these resources were implicitly considered (IPOT) and a simulation in which they were neglected (ILIM). We found that global cropland consumed >7200 km3 year−1 of green water in 1971–2000, representing 92% (ILIM) and 85% (IPOT), respectively, of total crop water consumption. Even on irrigated cropland, 35% (ILIM) and 20% (IPOT) of water consumption consisted of green water. An additional 8155 km3 year−1 of green water was consumed on grazing land; a further ∼44,700 km3 year−1 sustained the ecosystems. Blue water consumption predominated only in intensively irrigated regions and was estimated at 636 km3 year−1 (ILIM) and 1364 km3 year−1 (IPOT) globally, suggesting that presently almost half of the irrigation water stemmed from nonrenewable and nonlocal sources. Land cover conversion reduced global evapotranspiration by 2.8% and increased discharge by 5.0% (1764 km3 year−1), whereas irrigation increased evapotranspiration by up to 1.9% and decreased discharge by 0.5% at least (IPOT, 1971–2000). The diverse water fluxes displayed considerable interannual and interdecadal variability due to climatic variations and the progressive increase of the global area under cultivation and irrigation.
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Bioenergy with carbon capture and storage (BECCS) is considered an important negative emissions (NEs) technology, but might involve substantial irrigation on biomass plantations. Potential water ...stress resulting from the additional withdrawals warrants evaluation against the avoided climate change impact. Here we quantitatively assess potential side effects of BECCS with respect to water stress by disentangling the associated drivers (irrigated biomass plantations, climate, land use patterns) using comprehensive global model simulations. By considering a widespread use of irrigated biomass plantations, global warming by the end of the 21st century could be limited to 1.5 °C compared to a climate change scenario with 3 °C. However, our results suggest that both the global area and population living under severe water stress in the BECCS scenario would double compared to today and even exceed the impact of climate change. Such side effects of achieving substantial NEs would come as an extra pressure in an already water-stressed world and could only be avoided if sustainable water management were implemented globally.
Large‐scale biomass plantations (BPs) are a common factor in climate mitigation scenarios as they promise double benefits: extracting carbon from the atmosphere and providing a renewable energy ...source. However, their terrestrial carbon dioxide removal (tCDR) potentials depend on important factors such as land availability, efficiency of capturing biomass‐derived carbon and the timing of operation. Land availability is restricted by the demands of future food production depending on yield increases and population growth, by requirements for nature conservation and, with respect to climate mitigation, avoiding unfavourable albedo changes. We integrate these factors in one spatially explicit biogeochemical simulation framework to explore the tCDR opportunity space on land available after these constraints are taken into account, starting either in 2020 or 2050, and lasting until 2100. We find that assumed future needs for nature protection and food production strongly limit tCDR potentials. BPs on abandoned crop and pasture areas (~1,300 Mha in scenarios of either 8.0 billion people and yield gap reductions of 25% until 2020 or 9.5 billion people and yield gap reductions of 50% until 2050) could, theoretically, sequester ~100 GtC in land carbon stocks and biomass harvest by 2100. However, this potential would be ~80% lower if only cropland was available or ~50% lower if albedo decreases were considered as a factor restricting land availability. Converting instead natural forest, shrubland or grassland into BPs could result in much larger tCDR potentials ̶ but at high environmental costs (e.g. biodiversity loss). The most promising avenue for effective tCDR seems to be improvement of efficient carbon utilization pathways, changes in dietary trends or the restoration of marginal lands for the implementation of tCDR.
Large‐scale biomass plantations (BPs) are a common tool in climate mitigation scenarios to keep, for example, global mean temperatures below 2°C. However, thorough analyses from an Earth system perspective on the potentials and trade‐offs of such biomass plantations as conducted here are still missing. Using a spatially explicit biogeochemical process model, we find that the carbon extraction potentials are very limited due to the projected food demand of a growing world population which likely requires agricultural land expansion, unfavourable albedo changes caused by land transformation for BPs and the need to preserve natural ecosystems. Increasing conversion efficiencies for capturing biomass‐derived carbon and restoring degraded land for BPs could, however, notably raise the potentials.
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8.
Tipping elements in the Earth's climate system Lenton, Timothy M; Held, Hermann; Kriegler, Elmar ...
Proceedings of the National Academy of Sciences - PNAS,
02/2008, Volume:
105, Issue:
6
Journal Article
Peer reviewed
Open access
The term "tipping point" commonly refers to a critical threshold at which a tiny perturbation can qualitatively alter the state or development of a system. Here we introduce the term "tipping ...element" to describe large-scale components of the Earth system that may pass a tipping point. We critically evaluate potential policy-relevant tipping elements in the climate system under anthropogenic forcing, drawing on the pertinent literature and a recent international workshop to compile a short list, and we assess where their tipping points lie. An expert elicitation is used to help rank their sensitivity to global warming and the uncertainty about the underlying physical mechanisms. Then we explain how, in principle, early warning systems could be established to detect the proximity of some tipping points.
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This comment raises concerns regarding the way in which a new European directive, aimed at reaching higher renewable energy targets, treats wood harvested directly for bioenergy use as a carbon-free ...fuel. The result could consume quantities of wood equal to all Europe's wood harvests, greatly increase carbon in the air for decades, and set a dangerous global example.
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