Global Commons in the Anthropocene: World Development on a Stable and Resilient Planet

• Three decades of internationally coordinated research on the Earth system has led to the conclusion that Earth has entered a new geological epoch – the Anthropocene. The stability and resilience of the Earth system is now at risk. Yet, a stable Earth system is a prerequisite for human development. • Nine Planetary Boundaries determine Earth system resilience. Human activities have caused the Earth system to transgress four of these boundaries, namely climate, biodiversity, land-use change (deforestation) and biogeochemical cycles (predominantly overuse of phosphorus and nitrogen in fertilizers). • The Anthropocene changes our relationship with the planet and how societies view the “global commons”. One definition of the global commons currently used by international law names: the high seas; the atmosphere; Antarctica; and outer space – as the globally common resources that fall outside national jurisdictions. However, the stability and resilience of the Earth system is also common to all. This stability and resilience is dependent upon both the global commons as recognized under international law and also the resources within national jurisdictions, for example rainforests, sea ice, mangroves and biodiversity. • We argue that humanity must be the steward of the planet’s natural resources – the ecosystems, biomes and processes that regulate the stability and resilience of the Earth system, for example the carbon cycle. These are what we term the new “Global Commons in the Anthropocene”. • The UN Sustainable Development Goals and the Paris Agreement on Climate Change indicate a paradigm shift in the global response to safeguarding the Global Commons in the Anthropocene. • In the coming decades, four key socioeconomic megatrends will determine the trajectory of the Anthropocene: energy, food, water and urbanization. • Food, the world’s single largest user of fresh and underground water, and the single largest reason for transgressing Planetary Boundaries on nitrogen/phosphorus, land, and biodiversity. Transformation of the food system has the potential to improve personal, societal and planetary health and wellbeing. • Decarbonization of the global energy system is now of critical importance for a 1.5–2°C future global temperature increase line with the Paris Agreement. • Water, the source of life, is under severe pressure, and water stress and scarcity are increasing in many parts of the world. • By 2050, 75% of the world’s population will live in urban areas. This global shift requires a major focus on transformation to sustainable and livable urban environments, transportation and a circular economy. • A focus on these four interlinked sectors holds the best chance of protecting the global commons in the Anthropocene for human prosperity and wellbeing

Climate change: The necessary, the possible and the desirable Earth League climate statement on the implications for climate policy from the 5th IPCC Assessment

In time with this year's UN climate conference in Lima, a group of leading scientists, including Earth League members - a global alliance of prominent climate scientists - laid out in a joint paper the key elements of the "the necessary, the possible and the desirable" in relation to climate change. "We, as citizens with a strong engagement in Earth system science and socio-ecological dynamics, share the vision of a more equitable and prosperous future for the world, yet we also see threats to this future from shifts in climate and environmental processes," the scientists write. "Without collaborative action now, our shared Earth system may not be able to sustainably support a large proportion of humanity in the coming decades.. The authors concisely explain the high risks presented by cascading environmental vulnerabilities and positive feedback effects. They highlight that a transformation towards carbon-free energy systems is feasible, and would come with substantial benefits

Assessing the implications of water harvesting intensification on upstream-downstream ecosystem services: A case study in the Lake Tana basin

Water harvesting systems have improved productivity in various regions in sub-Saharan Africa. Similary, they can help retain water in landscapes, build resilience against droughts and dry spells, and thereby contribute to sustainable agricultural intensification. However, there is no strong empirical evidence that shows the effects of intensification of water harvesting on upstream-downstream social-ecological systems at a landscape scale. In this paper we develop a decision support system (DSS) for locating and sizing water harvesting ponds in a hydrological model, which enables assessments of water harvesting intensificatin on upstream-downstream ecosystem services in meso-scale watersheds. The DSS was used with the Soil and Water Assessment Tool (SWAT) for a case-study area located in the Lake Tana basin, Ethiopia. We found that supplementary irrigation in combination with nutrient application increased simulated teff ('Eragrostis tef', staple crop in Ethiopa) production up to three times, compared to the current practice. Moreover, after supplemental irrigation of teff, the excess water was used for dry season onion production of 7.66 t/a (median). Water harvesting, therefore, can play an important role in increasing local- to regional-scale food security through increased and more stable food production and generation of extra income from the sale of cash crops. The annual total irrigation water consumption was ~ 4%.30% of the annual water yield from the entire watershed. In general, water harveting resulted in a reduction in peak flows and an increase in low flows. Water harvesting substantially reduced sediment yield leaving the watershed. The beneficiaries of water harvesting ponds may benefit from increases in agricultural production. The downstream social-ecological systems may benefit from reduced food prices, reduced flooding damages, and reduced sediment influxes, as well as enhancements in low flows and water quality. The benefits of water harvesting warrant economic feasibility studies and detailed analyses of its ecological impacts

Hysteresis of tropical forests in the 21st century

Tropical forests modify the conditions they depend on through feedbacks at different spatial scales. These feedbacks shape the hysteresis (history-dependence) of tropical forests, thus controlling their resilience to deforestation and response to climate change. Here, we determine the emergent hysteresis from local-scale tipping points and regional-scale forest-rainfall feedbacks across the tropics under the recent climate and a severe climate-change scenario. By integrating remote sensing, a global hydrological model, and detailed atmospheric moisture tracking simulations, we find that forest-rainfall feedback expands the geographic range of possible forest distributions, especially in the Amazon. The Amazon forest could partially recover from complete deforestation, but may lose that resilience later this century. The Congo forest currently lacks resilience, but is predicted to gain it under climate change, whereas forests in Australasia are resilient under both current and future climates. Our results show how tropical forests shape their own distributions and create the climatic conditions that enable them.</p

Protecting irrecoverable carbon in Earth's ecosystems

Avoiding catastrophic climate change requires rapid decarbonization and improved ecosystem stewardship. To achieve the latter, ecosystems should be prioritized by responsiveness to direct, localized action and the magnitude and recoverability of their carbon stores. Here, we show that a range of ecosystems contain ‘irrecoverable carbon’ that is vulnerable to release upon land use conversion and, once lost, is not recoverable on timescales relevant to avoiding dangerous climate impacts. Globally, ecosystems highly affected by human land-use decisions contain at least 260 Gt of irrecoverable carbon, with particularly high densities in peatlands, mangroves, old-growth forests and marshes. To achieve climate goals, we must safeguard these irrecoverable carbon pools through an expanded set of policy and finance strategies.</p