cbd-ts-66-en

Part I: Impacts of Climate-related Geoengineering on Biological Diversity
been reduced by SRM, in comparison to unmitigated climate change. However, that is likely to be countered by
the avoidance of additional biogenic CO2 in the atmosphere (as much as 100 ppm by 2100, under an A2 SRES
scenario) as a feedback response to global warming, due to temperature-driven changes in the productivity and
decomposition of terrestrial biomass,199 particularly affecting Arctic regions.200
SRM will not address the effects of high CO2 concentrations on terrestrial ecosystems, such as favouring some
plant groups over others.201 However, high CO2 can have beneficial effects on plant productivity, reducing water
stress,202 and such positive impacts could be expected to continue under SRM.
4.1.5 Rate of environmental change and the termination effect
It is not just the magnitude, nature and distribution of environmental changes (from climate change or from solar
geoengineering) that will affect biodiversity and ecosystem services, but also the rate at which the changes take
place. In general, the faster an environment changes, the greater the risk to species.203 SRM, if effective, could
slow, halt or even reverse the pace of global warming much more quickly than mitigation measures (within
months, versus decades or longer), notwithstanding potential side effects. Therefore, it could either be deployed
as an “emergency response204, 205” in order to counter imminent threats, or more gradually to shave the peaks off
more extreme warming, in order to allow more time both for adaptive measures and natural adaptation,206 and
for effective mitigation measures to be implemented.
However, there is an additional issue to consider when evaluating the general effects of SRM on biodiversity and
ecosystem services: the so-called “termination effect”.
Atmospheric-based SRM techniques would only offset global warming as long as they are actively maintained.
Whilst abrupt discontinuation would be unplanned, there is inevitably risk of such an eventuality, due to political
instabilities or policy changes at either the national or international level; for example, in response to the occurrence
of regionally-severe extreme events. Such events would undoubtedly be perceived as due to the SRM action (with
consequences for public acceptability and international legal compensation), even if direct attribution could not
be scientifically proven. Such cessation of SRM that had been deployed for some time would, in the absence of
effective stabilization or reduction of atmospheric greenhouse gas concentrations, result in increased rates of
climatic change: all the warming that would have otherwise taken place (either over just a few years or several
decades) is projected to take place over a much shorter period.207
Under such circumstances, the rapid warming due to SRM termination would almost certainly have large negative
impacts on biodiversity and ecosystem services, with potentially severe socio-economic implications208 and these
effects would be more severe than those resulting from gradual climate change. Most plants, animals and their
interactions are likely to be affected, since current rates of anthropogenic climate change are already altering, or
are projected to alter, community structure,209 biogeochemical cycles,210 and fire risk.211
199 Matthews et al. (2009).
200 Schuur et al. (2008).
201 Collatz et al. (1998).
202 Long et al. (2004).
203 Chevin et al. (2010).
204 Solar Radiation Management Governance Initiative (SRMGI) (2011).
205 Rapid cooling due to full-scale SRM deployment could also itself have negative impacts for biodiversity, as well as potentially
triggering climatic instabilities.
206 Secretariat of the Convention on Biological Diversity (2009a).
207 Matthews & Caldeira (2007).
208 Goes et al. (2012).
209 Walther et al. (2002).
210 Zepp et al. (2003).
211 Golding & Betts (2008).
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