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Article

Holly Morgan, Saran Sohi, and Simon Shackley

Biochar is a charcoal that is used to improve land rather than as a fuel. Biochar is produced from biomass, usually through the process of pyrolysis. Due to the molecular structure and strength of the chemical bonds, the carbon in biochar is in a stable form and not readily mineralized to CO2 (as is the fate of most of the carbon in biomass). Because the carbon in biochar derives (via photosynthesis) from atmospheric CO2, biochar has the potential to be a net negative carbon technology/carbon dioxide removal option. Biochar is not a single homogeneous material. Its composition and properties (including longevity) differ according to feedstock (source biomass), pyrolysis (production) conditions, and its intended application. This variety and heterogeneity have so far eluded an agreed methodology for calculating biochar’s carbon abatement. Meta-analyses increasingly summarize the effects of biochar in pot and field trials. These results illuminate that biochar may have important agronomic benefits in poorer acidic tropical and subtropical soils, with one study indicating an average 25% yield increase across all trials. In temperate soils the impact is modest to trivial and the same study found no significant impact on crop yield arising from biochar amendment. There is much complexity in matching biochar to suitable soil-crop applications and this challenge has defied development of simple heuristics to enable implementation. Biochar has great potential as a carbon management technology and as a soil amendment. The lack of technically rigorous methodologies for measuring recalcitrant carbon limits development of the technology according to this specific purpose.

Article

Jorge H. García and Thomas Sterner

Economists argue that carbon taxation (and more generally carbon pricing) is the single most powerful way to combat climate change. Since this is so controversial, we need to explain it better, and to be precise, the efficiency gains are largest when the costs of abatement are strongly heterogeneous. This is often—but not always—the case. When it is not, standards can fill much the same role. To internalize the climate externality, economic efficiency calls for a global carbon tax (or price) that is equal to the global damage or the so-called social cost of carbon. However, equity considerations as well as existing geographical and sectoral differences in the effectiveness of carbon taxation at reducing emissions, suggest earlier implementation of relatively high taxation levels in some sectors or countries—for instance, among richer economies followed by a more gradual phase-in among low-income countries. The number of national and subnational carbon pricing policies that have been implemented around the world during the first years following the Paris Agreement of 2015 is significant. By 2020, these programs covered 22% of global emissions with an average carbon price (weighted by the share of emissions covered) of USD15/tCO2 and a maximum price of USD120/tCO2. The share of emissions covered by carbon pricing as well as carbon prices themselves are expected to consistently rise throughout the decade 2021–2030 and beyond. Many experts agree that the social cost of carbon is in the range USD40–100/tCO2. Anti-climate lobbying, public opposition, and lack of understanding of the instrument are among the key challenges faced by carbon taxation. Opportunities for further expansion of carbon taxation lie in increased climate awareness, the communicative resources governments have to help citizens understand the logic behind carbon taxation, and earmarking of carbon tax revenues to address issues that are important to the public such as fairness.

Article

Deforestation causes up to 10% of global anthropogenic carbon emissions. Reducing emissions from deforestation and degradation and enhancing forest carbon stocks can contribute to controlling greenhouse gas (GHG) emissions and limit global warming and climate change. However, global warming cannot be limited without decreasing the use of fossil fuel or emission-intensive energy sources. The forestry sector could contribute 7%–25% of global emissions reduction by 2020. Apart from emissions reduction and sink (mitigation), forests also provide cobenefits such as ecosystem services (providing food, timber, and medicinal herbs); biodiversity conservation; poverty reduction; and water quality, soil protection, and climate regulation. In 2005, the UNFCCC introduced a cost-effective mitigation strategy to reduce emissions from deforestation (RED) in developing countries. The UN’s initiative to reduce emissions from deforestation and forest degradation (REDD+) aims to transform forest management in developing countries, where the majority of tropical forests are located, using finances from developed countries. REDD+ seeks to reward actors for maintaining or restoring forests, acting as an economic instrument by putting a monetary value on every tonne of CO2 that is prevented from entering the atmosphere. Implementation of REDD+ requires economic and policy instruments that can help to control GHG emissions by enhancing carbon sinks, reducing deforestation and forest degradation, and managing sustainable forests. Payment for environmental services offers opportunities for either cofinancing or economic valuation in regard to REDD+ implementation. The challenge is to identify the most appropriate and cost-effective instrument. REDD+ fulfills the current needs for economic instruments and incentives that can be implemented with existing land use and forestry policies to control global GHG emissions. However, REDD+ requires forest governance, law enforcement, clarification of land and resource rights, and forest monitoring to work in the long term. REDD+ payments can be made for results-based actions, and the UNFCCC has identified potential ways to pay for them, but challenges remain, such as clarifying financing or funding sources, distribution of funding and sharing of benefits or incentives, carbon rights, and so on. Different aspects pf the implementation, effectiveness, and scale of REDD+ and their interactions with economic, social, and environmental benefits are important for successful REDD+ implementation.

Article

Evolution of international climate change policy and processes commenced in 1990 with the United Nations Framework Convention on Climate Change (UNFCCC), which made the first global attempt to provide an intergovernmental platform for addressing the effects of climate change. Since then, major advances in the international dialog occurred from 1995 to 2004 during the Kyoto Protocol. However, the Kyoto Protocol outcome was not considered a major success in terms of reducing global emissions, although it succeeded in advancing global market-based flexible mitigation mechanisms, such as emissions trading, joint implementation, and the clean development mechanism. A turnaround in the global approach occurred with the Paris Agreement in 2015, which represented a major turning point in the climate debate, with a bottom-up approach allowing states to set their own emission targets. In addition, the Paris Agreement was the catalyst for formation of bodies and institutions that promote negotiated climate change themes and has permitted countries to work together to share direct practical approaches for tackling climate change. The success of the Paris Agreement can be seen as more countries commit to nationally determined contribution targets. In addition, the practical implication of the bottom-up approach for institutional investors and corporate engagement is evident from the increase in the number of global climate change litigation cases brought against corporations and financial institutions that breach climate change obligations. Going forward, some of the climate change negotiation issues of concern that have yet to be resolved include the differences in contributions required by developed nations as opposed to developing nations, sometimes referred to as the North–South divide in climate change negotiations, the issue of loss and damage associated with climate change events, such as tropical cyclones and storms, and how to account for non-economic loss and damage caused by climate change events.

Article

Human beings are part of natural ecosystems and depend on them for their survival. In a rapidly changing environment and with increasing urbanization, this dependence is challenged. Natural environments affect human health and well-being both directly and indirectly. Urban green and blue areas provide opportunities for stress recovery and physical activity. They offer spaces for social interactions in the neighborhood and places for children’s play. Chronic stress, physical inactivity, and lack of social cohesion are three major risk factors for noncommunicable diseases, and therefore abundant urban greenery is an important asset for health promotion. Through numerous ecosystem services natural environments play a fundamental role in protecting health. Various populations depend on nature for basic material, such as fresh water, wood, fuel, and nutritious food. Biodiverse natural areas are also necessary for regulating the environment and for mitigating and adapting to climate change. For example, tree canopy cover can reduce the urban heat island effect substantially, preventing excess morbidity during heat waves. This natural heat-reducing effect also lessens the need for air conditioning systems and as a consequence decreases energy spending. Urban trees also support storm-water management, preventing flooding and related health issues. Air pollution is a major threat to population health. Urban trees sequester pollutants and, even though the effect may be relatively small, given the severity of the problem it may still have some public-health implications. The evidence around the effects of natural environments on health and well-being is steadily increasing. Several pathways and mechanisms are suggested, such as health services through functional ecosystems, early life exposure to biodiverse microbiota, which is important for the immune-system development, and sensory exposure, which has direct neurobiological impact supporting cognitive development and stress resilience. Support for several pathways is at hand that shows lower mortality rates and prevalence of cardiovascular and respiratory diseases, healthier pregnancy outcomes, reduced health inequalities, and improved mental health in urban areas with greater amounts of green and blue space. Altogether, the interactions between healthy natural environments and healthy people are multiple and complex, and require interdisciplinary attention and action for full understanding and resilient development of both nature and human beings.