ViewpointBioengineering the biosphere?
Introduction
In a few human generations, our planet is likely to experience large-scale changes that will jeopardise the stability of our complex social and economic structures. Energy and demographic crises, biodiversity declines, increasingly frequent extreme events, along with water shortage and crop failure associated to climate change are already sending us warning signals (Scheffer et al., 2001, Scheffer and Carpenter, 2003, Scheffer, 2009, Dawson et al., 2011; Lenton, 2011a; Barnovsky et al., 2012). We live in a time where the knowledge of our planet is greater than ever and the potential threads seem rather well defined. Scientists have depicted a grim perspective of our future. We are a major transforming force that is rapidly pushing our planet towards new, undesirable states. A consensus has emerged from climate science about a future, hotter planet that will make life difficult, if not simply incompatible, with a sustainable society (Lenton et al., 2008). We have enjoyed a favourable window of 10,000 years, the so called Holocene period, where humans have been able to flourish as a dominant, creative and rapidly expanding species but also as a global geological force. The new human-driven era that emerges from the Industrial Revolution, the so called Anthropocene, is dominated by an increasingly obvious impact of human activities that are pushing the Earth outside its regulatory capacity (Steffen et al., 2011).
As it occurs with many other complex systems (May, 1977) continuous changes in parameters that control the state of given system often end up in catastrophic shifts once tipping points are reached (Scheffer, 2009, Solé, 2011; Hughes et al., 2013). This is the case of the average concentration of carbon dioxide: once some critical levels are reached, our current climate state is likely to be replaced by another global pattern resulting from a runaway greenhouse effect (Solomon et al., 2007, New et al., 2011). A macroecological analysis of energy use and economic activity also indicates that the current tendency might end in a social and economic collapse (Rockstrom et al., 2009). Similarly, many ecological systems will face rapid declines towards degraded and even bare systems with no species left (Suding et al., 2004). This is illustrated by arid and semiarid ecosystems (Rietkerk and van de Koppel, 1997, Scanlon et al., 2007, Kéfi et al., 2007, Solé, 2007) where warming, steady declines in rainfall and increased grazing will trigger rapid changes towards a desert state and are specially vulnerable (Thornton et al., 2011). Evidence for such sudden changes exist, as shown by the shift from a green Sahara to the current desert state, which took place 5500 years ago (Foley et al., 2003). Rainforest ecosystems, reefs and boreal forests might also face serious declines (Barnovsky et al., 2012, Hughes et al., 2013). In some cases, as illustrated by the collapse of fisheries, they have already occurred while the awareness and reactivity of society to such sudden loss has been far from optimal (Scheffer et al., 2003).
Many studies have addressed possible ways for remediating these potentially catastrophic situations. Humans too have been effectively operating as ecosystem engineers (Vitousek et al., 1997) by adapting the biosphere to their needs, while expanding their populations in a hyper exponential fashion. Because our long-term influence, vast amounts of energy-intensive fossil fuels have been used to power our civilisation, reinforced by the accelerated growth of agriculture from the Neolithic revolution. Profound alterations of the water and nitrogen cycles are a direct consequence of these unsustainable practices. Moreover, an ongoing rearrangement of biotic systems has been taking place, mainly due to habitat loss and biological invasions (Elton, 1958, Drake et al., 1989). By doing that, we are changing the face of our biosphere, placing ourselves close to a planetary-level critical transition. Can the situation be reverted?
Existing approaches, to be summarised below, include reforestation, geo-engineering and emission cuts, among others. However, the scale of the problem, the staggering economic costs and its accelerating pace constitute a major barrier to restore previous states in a sustainable way (Folke et al., 2011). Moreover, we need to face the nature of our biosphere as a complex adaptive system with multiple interacting species, nonlinear responses, complex feedbacks and self-organizing patterns (Levin, 2002, Solé and Levin, 2002). There is a strong asymmetry between cumulative anthropogenic impacts and our slow and limited capacity for counterbalancing them on time. Such asymmetry implies that we might have a narrow time window to properly react to the challenge. In this paper I suggest a rather different approach, which requires an engineering perspective, grounded in the design of modified life forms and intervention. But, above all, requires a new merging of disciplines, particularly at the unexplored boundaries between synthetic biology and ecological theory. Because it requires humans as agents for Earths transformation, the remediation strategies suggested here imply a modification of natural ecosystems. This is, no doubt, a controversial matter (Callaway, 2013). The advantages and drawbacks of this approach, along with implementation strategies, are outlined below.
Section snippets
Terraforming Earth?
Restoring a sustainable Earths state necessarily requires to confront the scales of space, time and energy on the planetary level. That means that whatever the solutions found, they go beyond any human standard engineering scale. Before looking at our own biosphere, let us first make a turn by considering the other single scenario where such engineering problem has been proposed, namely the problem of “Terraforming” Mars (McKay et al., 1991). The idea is, in a nutshell, to introduce artificial
Synthetic ecosystems
The proposal described here originates from the assumption that a synthetic organism can act, in some circumstances, as ecosystem engineer (Jones et al., 1994) capable of modifying the existing energy balances and/or nutrient flows. In nature, bacteria and microscopic algae in particular have played a major role in shaping our Earths climate (Kasting and Siefert, 2002, Falkowski et al., 2008, Lenton and Watson, 2011a, Lenton and Watson, 2011b) and could help us restore lost balances. Such
Predicting the outcome
In order to address the problem of accidental release of modified organisms, protocols for contention appeared as soon as genetic engineering started to develop. However, the early claims of the impact of recombinant DNA technology have been shown to be largely unfounded (Berg and Singer, 1995). Synthetic biology has raised similar concerns and different biosafety protocols have been established. In fact, the design of new organisms that perform given functions can include, as part of the new
Conclusions and discussion
What can be the impact of terraforming our own planet? Should we even consider that possibility? Can we deal with the complexity associated to such scenario? Some have compared geoengineering approaches to climate remediation with the Manhattan project (Michaelson, 1998) but I think the right dimensions in terms of the challenge are better met with the proposal outlined here. An intervention that can modify the biosphere in controlled ways to reach a new steady state compatible with a planet
Acknowledgments
The author would like to thank the members of the Complex Systems Lab and many colleagues at the Santa Fe Institute for fruitful discussions. Special thanks to Daniel Amor, Ernesto Azzurro, Steve Carpenter, Victor de Lorenzo, Salvador Duran-Nebreda, Santiago Elena, Harold Fellermann, Joaquim Garrabou, Tim Lenton, Simon Levin, John McCaskill, Raul Montanez, Melanie Moses, Manuel Porcar, Juli Peretó, Stuart Pimm, Irene Poli, Francesc Posas, Pere Puigdomènech, Steen Rasmussen, Carlos
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