10 November 2016
CBD Report Highlights Uncertainties of Geoengineering Assessment
UN Photo/Mark Garten
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The Secretariat of the Convention on Biological Diversity (CBD) has reported on potential impacts of geoengineering techniques, such as carbon dioxide removal and sunlight reflection methods, on biodiversity.

It concludes that biodiversity is affected by a number of drivers of change that will themselves be impacted by proposed geoengineering techniques.

October 2016: The Secretariat of the Convention on Biological Diversity (CBD) has reported on the potential impacts of geoengineering techniques on biodiversity and regulatory developments. The technical report provides an update on these issues following 2012 technical studies on the impacts of climate-related geoengineering on biodiversity and the regulatory framework for climate-related geoengineering relevant to the Convention.

Authored by P. Williamson and R. Bodle and published following a peer-review process, the report examines the potential impacts on biodiversity of climate geoengineering achieved by removal of carbon dioxide (CO2) or other greenhouse gases (GHG), and sunlight reflection methods (SRM) and other physically-based techniques. It considers: the impacts of such methods on the drivers of biodiversity loss, including the potential decrease in the climate change driver from effective geoengineering techniques; changes in other drivers, including land use change, that are inevitably associated with some geoengineering approaches; and the other positive and negative side-effects of specific techniques.

The report observes that climate change is already affecting biodiversity, such as through ocean acidification, and further impacts are inevitable. It addresses scenarios of future climate change to 2100 that are likely to keep global average temperature increases within a limit of 2°C above pre-industrial levels, which mostly rely on technologies for carbon dioxide removal (CDR) as well as emission reductions, with pathways that feature net negative emissions in the second half of the century.

On CDR, the authors conclude that: the potential to employ CDR at scale is highly uncertain; the removal of a given quantity of a greenhouse gas would not fully compensate for an earlier “overshoot” of emissions; and the large-scale deployment of bioenergy with carbon capture and storage (CCS) seems likely to have significant negative impacts on biodiversity through land use change. While ecosystem restoration, including reforestation and appropriate afforestation, can contribute to removing CO2 and provide substantive biodiversity co-benefits, the report notes, these activities are insufficient on their own to remove carbon at the scale required in most current scenarios.

Storing carbon in geological formations beneath the seafloor can lead to marine leakage and local ocean acidification.

Other key messages on CDR note that: biochar may potentially contribute to CO2 removal under certain circumstances, and the technique applied to agricultural soils may offer productivity co-benefits; and the viability of alternative negative emission techniques such as direct air capture, enhanced weathering and ocean fertilization remains unproven. The report notes that CO2 or other GHGs captured from the atmosphere must be stored in some form, and options include vegetation, soils, charcoal, or geological formations. On storing carbon in geological formations beneath the seafloor, experimental studies indicate that marine leakage could cause local ocean acidification, but with relatively localized environmental impacts. Other forms of storage in the ocean are considered to have unacceptable risks and are not allowed under the London Convention and Protocol.

On sunlight reflection methods (SRM), the report notes that recent studies and assessments have confirmed that SRM techniques could slow, stop or reverse global temperature increases. However, it highlights high levels of uncertainty about their other impacts, which could present significant new risks to biodiversity. For example, models suggest that SRM could slow the loss of Arctic sea ice, but would create unacceptable climatic impacts elsewhere. Similarly, SRM may benefit coral reefs by decreasing temperature-induced bleaching, but, under high CO2 conditions, it may also increase, indirectly, the impacts of ocean acidification.

The report further notes that: the use of sulphur aerosols for SRM would be associated with a risk of stratospheric ozone loss; the climatic effectiveness of marine cloud brightening depends on assumptions made regarding micro-physics and cloud behavior, and many associated issues are still highly uncertain; large-scale changes in land and ocean surface albedo do not seem to be viable or cost-effective; and cirrus cloud thinning, a technique aimed at increasing heat loss, may have potential to counteract climate change, but its feasibility and potential impacts have received little attention.

On socioeconomic and cultural considerations, the report underscores that where surveyed, the public acceptability of geoengineering is generally low, particularly for SRM. Nevertheless, studies in a range of countries have found broad approval for research into both CDR and SRM techniques, provided that the safety of such research can be demonstrated.

With regard to the regulatory framework, the report draws attention to the 2013 amendment to the London Protocol to regulate the placement of matter for ocean fertilization and other marine geoengineering activities, which, once entered into force, will strengthen the regulatory framework for ocean fertilization activities and provide a framework for the further regulation of other marine geoengineering activities.

The authors suggest that science-based global, transparent and effective control and regulatory mechanisms may be most needed with regard to geoengineering techniques that have a potential to cause significant adverse transboundary effects, and those deployed in areas beyond national jurisdiction and in the atmosphere. They identify lack of regulatory mechanisms for SRM as a major gap.

Finally, the authors underscore that biodiversity is affected by a number of drivers of change that will themselves be impacted by proposed CDR and SRM geoengineering techniques. [Publication: CBD Technical Series no. 84: Update on Climate Geoengineering in Relation to the Convention on Biological Diversity: Potential Impacts and Regulatory Framework] [2012 CBD Technical Reports on Geoengineering] [CBD Webpage on Climate-related Geoengineering and Biodiversity]

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