Potential geoengineering options present significant threats to biodiversity but the possibly greater threat from climate change means that research into the subject needs to continue, a United Nations report has concluded.
Alongside efforts to reduce the amount of greenhouse gases (GHGs) humanity is pumping into the atmosphere, geoengineering proposes a raft of techniques that actively intervene in the earth system to try to limit climate change.
Such techniques fall into two categories. The first, carbon dioxide removal (CDR), or negative emissions technologies, aims to draw down large quantities of carbon dioxide (CO2) directly from the air and then store it or use it.
The second category, known as solar radiation management, would work to reduce sunlight from passing through the atmosphere and reflect it back into space.
Some 90 percent of the Intergovernmental Panel on Climate Change (IPCC) scenarios that would allow the planet to keep within 2°C of warming above pre-industrial temperatures assume widespread uptake of negative emissions technologies.
“Climate geoengineering is what countries have agreed to do, although they haven’t really realized that they’ve agreed to do it,” lead author of the report, the University of East Anglia’s Phil Williamson, told Bloomberg news.
The report draws together the latest research on the effects of such techniques on biodiversity, building on a paper produced by Williamson published in February that warned that the risks to ecosystem losses were too risky and that the focus should remain on mitigation instead.
The new report offers more detail on such risks. In particular, the authors warn that large-scale deployment of bioenergy with carbon capture and storage (BECCS) will have significant negative impacts on biodiversity through land-use change. If this technique were deployed at a scale presumed in most IPCC scenarios, several hundred million hectares of land would have to be converted for this purpose. In addition, this would require a doubling of agricultural water demand and fertilizer for bioenergy crops.
A second technique the authors are especially critical of, ‘ocean fertilization’ or enhancing ocean productivity by stimulating phytoplankton growth through nutrient addition. They argue that biodiversity risks and uncertainties are high, and would likely only sequester small amounts of CO2 anyway.
Nevertheless, despite the dangers, the authors now conclude that given the scale of the danger from the continued rise in atmospheric GHG concentrations, and the relatively limited mitigation efforts by governments, further research into geoengineering techniques should continue. They also note that some options are more effective, present less of a threat to biodiversity and even may cost less than others. They describe carbon capture and storage as one of the better choices, and the cost of direct air capture of CO2 technology while still high is falling steadily. Further research into so-called enhanced weathering (GHG-absorbing rocks) in particular warrants support, they argue.
The authors also stress the need for a transparent, global governance framework for such activities, particularly for those with potential to cause significant adverse effects across borders.
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