• Energy Research

Crossing the boundaries in global sustainability The planetary boundary (PB) concept, introduced in 2009, aimed to define the environmental limits within which humanity can safely operate. This approach has proved influential in global sustainability policy development. Steffen et al. provide an updated and extended analysis of the PB framework. Of the original nine proposed boundaries, they identify three (including climate change) that might push the Earth system into a new state if crossed and that also have a pervasive influence on the remaining boundaries. They also develop the PB framework so that it can be applied usefully in a regional context. Science , this issue 10.1126/science.1259855

A transition to a decentralised, decarbonised energy system for the domestic sector is constrained by the difficulty of obtaining energy balance between fluctuating demand and the intermittent, non-dispatchable power supply delivered by most renewables. A microgrid system including a mix of renewable generation technologies, energy storage and demand response (DR) systems has been modelled using a linear programming approach, based on real world data of residential energy consumption and weather variables. This model allows the exploration of the effects of fluctuations in demand and supply, microgrid scale and configuration, energy management options and alternative optimisation criteria. The model demonstrates quantitatively that a mixed-renewables microgrid system can reduce demand fluctuations and improve energy balance. Peak demand hour fluctuations were reduced by up to 19% for a simulated microgrid containing 144 households with one renewable unit and four batteries per household, with a renewables mix of 83% photovoltaic (PV) panels and 17% wind turbines. With this system, the demand on macrogrid energy supply was reduced by 16%, CO2 emissions associated with energy use were reduced by 10% for all hours of operation, and by 74% during the hours of renewable supply. These findings suggest that microgrids using contemporary technologies can contribute significantly to CO2 mitigation targets.

The planetary boundaries framework proposes quantified guardrails to human modification of global environmental processes that regulate the stability of the planet and has been considered in sustainability science, governance, and corporate management. However, the planetary boundary for human freshwater use has been critiqued as a singular measure that does not reflect all types of human interference with the complex global water cycle and Earth System. We suggest that the water planetary boundary will be more scientifically robust and more useful in decision-making frameworks if it is redesigned to consider more specifically how climate and living ecosystems respond to changes in the different forms of water on Earth: atmospheric water, frozen water, groundwater, soil moisture, and surface water. This paper provides an ambitious scientific road map to define a new water planetary boundary consisting of sub-boundaries that account for a variety of changes to the water cycle.

Abstract The planetary boundaries framework defines a safe operating space for humanity. To date, these boundaries have mostly been investigated separately, and it is unclear whether breaching one boundary can lead to the transgression of another. By employing a dynamic global vegetation model, we systematically simulate the strength and direction of the effects of different transgression levels of the climate change boundary (using climate output from ten phase 6 of the Coupled Model Intercomparison Project models for CO2 levels ranging from 350 ppm to 1000 ppm). We focus on climate change-induced shifts of Earth’s major forest biomes, the control variable for the land-system change boundary, both by the end of this century and, to account for the long-term legacy effect, by the end of the millennium. Our simulations show that while staying within the 350 ppm climate change boundary co-stabilizes the land-system change boundary, breaching it (>450 ppm) leads to critical transgression of the latter, with greater severity the higher the ppm level rises and the more time passes. Specifically, this involves a poleward treeline shift, boreal forest dieback (nearly completely within its current area under extreme climate scenarios), competitive expansion of temperate forest into today’s boreal zone, and a slight tropical forest extension. These interacting changes also affect other planetary boundaries (freshwater change and biosphere integrity) and provide feedback to the climate change boundary itself. Our quantitative process-based study highlights the need for interactions to be studied for a systemic operationalization of the planetary boundaries framework.

Non-technical summary Transformation of the world towards sustainability in line with the 2030 Agenda requires progress on multiple dimensions of human well-being. We track development of relevant indicators for Sustainable Development Goals (SDGs) 1–7 against gross domestic product (GDP) per person in seven world regions and the world as a whole. Across the regions, we find uniform development patterns where SDGs 1–7 – and therefore main human needs – are achieved at around US$15,000 measured in 2011 US$ purchasing power parity (PPP). Technical summary How does GDP per person relate to the achievement of well-being as targeted by the 2030 Agenda? The 2030 Agenda includes global ambitions to meet human needs and aspirations. However, these need to be met within planetary boundaries. In nascent world-earth modelling, human well-being as well as global environmental impacts are linked through economic production, which is tracked by GDP. We examined historic developments on 5-year intervals, 1980–2015, between average income and the advancement on indicators of SDGs 1–7. This was done for both seven world regions and the world as a whole. We find uniform patterns of saturation for all regions above an income threshold somewhere around US$15,000 measured in 2011 US$ PPP. At this level, main human needs and capabilities are met. The level is also consistent with studies of life satisfaction and the Easterlin paradox. We observe stark differences with respect to scale: the patterns of the world as an aggregated whole develop differently from all its seven regions, with implications for world-earth model construction – and sustainability transformations. Social media summary Reaching human well-being #SDGs takes GDP levels of $15k. This may help shape transformation to a world that respects #PlanetaryBoundaries.

Ecosystem services are defined as the ecological and socio-economic value of goods and services provided by natural and semi-natural ecosystems. Ecosystem services are being impacted by many human induced stresses, one of them being nitrogen (N) deposition and its interactions with other pollutants and climate change. It is concluded that N directly or indirectly affects a wide range of provi- sioning, regulating, supporting and cultural ecosystem services, many of which are interrelated. When considering the effects of N on ecosystem services, it is important to distinguish between different types of ecosystems/species and the protection against N impacts should include other aspects related to N, in addition to biodi- versity. The Working Group considered the following priorities of ecosystem services in relation to N: biodiversity; air quality/atmosphere; ecosystem changes; NO3 leaching; climate regulation and cultural issues. These are the services for which the best evidence is available in the literature. There is a conflicting interest between greenhouse gas ecosystem services and biodiversity protection; up to some point of increasing N inputs, net greenhouse gas uptake is improved, while biodiversity is already adversely affected.