Geoengineering is a word that means many things to many people. Formally defined as the "deliberate intervention in the climate system to counteract man-made global warming", for some scientists it represents a cheap and effective way to protect our planet from the ravages of climate change. To others it's symptomatic of technological hubris: a grand, doomed plan to control every aspect of our ecosystem. Dig past the rhetoric though and you find a science that's still in infancy, being developed by scientists around the globe, almost as a last resort in the (now very possible) event that on-going efforts to avert climate catastrophe by reducing global emissions fail.
Current research on geoengineering is focused on either removing carbon dioxide from the Earth's atmosphere or reducing global warming by reflecting more solar radiation away from the planet. Most proposals to achieve these goals rely on physical engineering solutions, cloud seeding for instance. A more expansive reading of "geoengineering"though, leads to several intriguing ideas on using synthetic biology to remedy the effects of intensive industrialisation/pollution on the environment.
I. PALE BLUE DOT
In 1980, the US Supreme Court issued a ruling that changed the status of living organisms forever. In Diamond v. Chakrabarty the court affirmed the right of inventors to patent living organisms that had been modified for some purpose. In this case, the patent was granted to a genetically engineered creature called the Superbug. The Superbug was a strain of Pseudonomas putida that could break down crude oil, and was posited as a tool to deal with oil spills. Since then, there's been a lot of work in developing such organisms, spawning a field of science called bioremediation that seeks to undo the damage human industry causes the environment.
Now, a group of scientists are advocating the use of such organisms on a global scale to help mitigate the effects of climate change. Their, very SciFi-ish, ideas include: modifying particular species of bacteria that exist in harsh environments like deserts and equipping them with water harvesting capabilities; releasing entire stretches of DNA into a biosphere and allowing them to spread, equipping any host creature with water/temperature sensing capabilities, or releasing bacteria into the oceans that can cause pieces of plastic to stick to each other, solving the scourge of microplastic pollution.
These and other ideas find few takers though, and carry some real risks. We would have to be prepared to deal with the fact that any man-made bacteria released into a particular part of the world might escape a particular ecosystem, potentially wreaking havoc in others. Biological entities evolve, and evolution might change released modified bacteria in unpredictable ways.
These are concerns synthetic biologists are tackling head on. In the last five years, we've made tremendous progress in engineering 'kill-switches' that could allow us to precisely control engineered bacteria in natural ecosystems. We've also developed bacteria which have been so extensively engineered that they cannot interact with other life-forms very well, or cannot reproduce, hence limiting the potential spread of synthetic DNA. Yet, biologists are ever-aware of the conceit involved in predicting biological futures and for the moment these bacteria will remain in petri dishes in labs around the world.
II. THE RED PLANET
The largest concern with biological geo-engineering is the fact that we might cause dangerously irreversible changes to the only habitable planet we know of. This is why, a group of scientists including NASA researchers are exploring biological options in terraforming Mars. The hopes are many, ranging from making Mars human-habitable (paving the way for eventual human colonisation), to using the red planet as a test-bed for ecosystem engineering whose lessons might then rescue the Earth from climate catastrophe. Less futuristic scenarios include the possibility of employing bacteria to harvest resources directly from Mars, or recycling consumable resources like waste-water, making manned Mars-missions a cheaper and easier endeavour. Most experts agree though that terraforming, the process of completely changing Mars' atmosphere is a process that could take centuries. A nearer-term option is something called para-terraforming. Paraterraforming envisions making smaller, enclosed spaces on Mars habitable for humans. Previous experiments in paraterraforming conducted on Earth have met with little success; however the prospect of engineering organisms specifically for terraforming makes this a more feasible proposition.
Some however, question the ethics of using Mars as a lab-bench. One argument is that any human attempt at terraforming Mars might destroy or alter any remnant, hitherto undiscovered life on the planet. Another, that seeding Mars with terrestrial life may change a potential independent development of biological life on the planet in the distant future. These are minority opinions however. A view that, in my opinion, holds more merit suggests that the creation of Mars as a back-up planet might hinder attempts to mitigate anthropogenic climate change and pollution here on Earth.
III. A LAST RESORT
There are two forms of climate change mitigation on the table at the moment, passive and active.Passive mitigation uses methods that are easier to swallow for most, reducing global consumption, stricter pollution controls, and switching to low-carbon sources of energy. The problem however lies in the fact that passive mitigation alone might not be enough to limit global warming to the 2°C threshold set by the Paris Agreement. Indeed, experts are highly sceptical that limiting warming to even 4°C is feasible given current trends. And the difference between a 2°C and 4°C limit is that the latter will result in massive droughts, flooding on an unprecedented scale and food shortages.
In this scenario, several climate experts have called for more drastic measures including non-biological geoengineering technologies cloud-seeding. In fact some estimates claim that cloud-seeding on a large enough scale might even bring global temperatures down to below pre-industrial levels. In this scenario then, would we even need a biological solution that might carry more risk?
A possible benefit of biological remediation is of course that we might be able to rescue ecosystems that are on the brink of collapse, something that physical solutions like cloud seeding might never be able to achieve. Biological solutions can address biological problems in a manner that purely physical measures might struggle to. Another aspect of synthetic biology, the de-extinction of extinct species, is something that might supplement the reduction in global warming with the restoration of lost biospheres.
On the policy front geoengineering is a topic that's often scoffed at or neglected in favour of discussions such as emissions reduction. The reasons for this are legitimate, though given the current political climate with the US backing out of climate accords, the dream of a 2°C reduction in global warming seems to be growing ever more distant. Science agencies across the world are waking up to this fact, and just a couple of months ago China announced the world's largest geoengineering research program. As of now, geoengineering remains a last resort, and biological measures even more so.
This isn't stopping scientists from experimenting with it though, and nor should it.