Our planet is experiencing an accelerated process of change associated to a variety of anthropogenic phenomena. The future of this transformation is uncertain, but there is general agreement about its negative unfolding that might threaten our own survival. Furthermore, the pace of the expected changes is likely to be abrupt: catastrophic shifts might be the most likely outcome of this ongoing, apparently slow process. Although different strategies for geo-engineering the planet have been advanced, none seem likely to safely revert the large-scale problems associated to carbon dioxide accumulation or ecosystem degradation.
An alternative possibility (see R Solé, "Bioengineering the Biosphere?", Ecological Complexity 2015) is inspired in the rapidly growing potential for engineering living systems. It would involve designing synthetic organisms capable of reproducing and expanding to large geographic scales with the goal of achieving a long-term or a transient restoration of ecosystem-level homeostasis. Such a regional or even planetary-scale engineering would have to deal with the complexity of our biosphere. It will require not only a proper design of organisms but also understanding their place within ecological networks and their evolvability. This is a likely future scenario that will require integration of ideas coming from currently weakly connected domains, including synthetic biology, ecological and genome engineering, evolutionary theory, climate science, biogeography and invasion ecology, among others.
We are exploring this problem using mathematical, computational and experimental approaches. Four different classes of "Terraformation motifs" are being studied. Two of them involve the engineering of symbiotic interactions. The synthetic microbe and another, resident species (a plant or another microbe, for example) would share a common mutualistic interaction that would be designed in order to force the synthetic one to be host-dependent while it enhances the survival and spread of its host. In a different scheme, the synthetic species would be designed in order to survive attached (and perhaps degrading it) to a human-produced substrate, such as plastic debris. Finally, a fourth scheme deals with designed organisms that would operate in a special class of wasteland or sewage, thus confined to a habitat that is of no profit to humans. All these schemes could be used to redesign existing (but perhaps degraded or endangered) ecosystems as a way of capturing carbon dioxide, improving nitrogen fixation and/or moisture retention (as it would be desirable in arid ecosystems).