Figure 1 illustrates the number of species on the IUCN red list which are threatened by various human activities and impacts; climate change is notably much less severe than other factors like over-exploitation or agricultural activity. However, the authors of this study acknowledge that climate change will become an increasing threat in the future as temperatures continue to rise (Maxwell et al., 2016).
Figure 1: The number of species on the IUCN red list affected by a variety of threats. (Source: Maxwell et al., 2016).
Mark Urban (2015) of the University of Connecticut combined the data of 131 extinction studies to produce a global estimate of the impacts of climate change on biodiversity. The study found that the Paris Agreement target of 2-degree warming would increase the percentage of species facing extinction risk from 2.8% (present) to 5.2%. A previous blog post discussed the difficulties of meeting this target, which should be frightening because a 4.3-degree rise could see 16% of species (or 1 in 6) facing a risk of extinction.
In 2010, news headlines heralded that the UN Convention on Biological Diversity (CBD) had 'banned geoengineering' at its 10th Conference of the Parties (COP). A more accurate statement would be that the 193 signatories had agreed to postpone large-scale projects, but allow small-scale research, until its impacts on the environment and biodiversity are fully understood.
The Secretariat of the CBD have been leading research examining the links between geoengineering and biodiversity, with a technical report published in 2012 and an updated report in 2016.
Regarding CDR methods, these reports suggest that the impacts depend largely on the scale and exact implementation but acknowledge that they are expected to mitigate the biodiversity impacts of climate change, and most methods would also help tackle ocean acidification. The reports note, however, that the scale at which methods such as BECCS are included in IPCC models would require land-use change on such a large scale that the impacts would partially offset or exceed the carbon sequestered as biomass.
Regarding SRM methods, the report admits that many impacts on biodiversity are uncertain due to the immense changes in ecosystem dynamics that would occur if global dimming were combined with no changes to CO2. However, it is noted that only species threatened by rising temperatures would be protected, and not those threatened by ocean acidification or greenhouse gas emissions. The report stresses the potentially grave dangers to biodiversity and ecosystem services of any rapid termination of prolonged significant SRM techniques.
Geoengineering, particularly CDR methods, are capable of mitigating the climate change impacts on biodiversity, but nothing would be more effective than simply reducing CO2 emissions initially.
It may be better to reverse the issue though and enhance biodiversity as a means of achieving a reduction in CO2. This 'natural geoengineering', Oswald Schmitz of Yale University argues, works by preserving top predators to control herbivore populations and thus maximise the amount of CO2 an ecosystem can store.
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