The landing of the explorer Curiosity on Mars is a fantastic affirmation of the extraordinary technical capacities of humans. A series of remote, high risk choreographed moves saw a small mobile laboratory alight on another planet. A publicly stated mission of the Curiosity is to discover if life has ever, or indeed does still, exist on the Red Planet. But if we found life we would not understand its ecology, because we barely understand life on Earth.
Mars and Venus, our nearest planetary neighbours, have extremely hostile atmospheres.
Venus is a run-away greenhouse planet, with a temperature greater than 450 degrees Celsius and an atmosphere made up of clouds of sulphuric acid. Mars is a dead, cold, dry place with a mean annual surface temperature below -60 degrees Celsius.
The striking difference between these neighbours and Earth is, of course, life. If Curiosity were deployed in any environment on Earth it would discover life – this is a living planet. It is the totality of all life which produces a biosphere that makes the Earth so distinct from the icehouse of Mars and the greenhouse of Venus.
We can understand life in a chemical sense - such as the strands of DNA that encode instructions for the functioning and reproduction of living things, and the biogeochemistry involved in the cycling of inorganic and organic matter such as carbon and nitrogen. But we remain baffled by the interactions amongst living things.
The science of these interactions is ecology. At the core of ecology are feedbacks that control bio-geochemical cycles and maintain biodiversity. Conundrums in ecology abound. For instance, why don’t herbivores consume all the plants? Why is there so much diversity in lifeforms when functioning ecosystems can be made up of just a few species? We suspect the answers lie with complex interactions that control plant and animal populations. The devilish complexity of ecological feedbacks and interactions defies mainstream scientific analytical tools. It is for this reason that ecologists are remarkably bad at making reliable predictions about how ecosystems will change in response to stresses and disturbances.
The complexity of ecology cannot be adequately incorporated into global climate models. It is therefore impossible to predict with any certainty how the Earth system will responds to greenhouse gas pollution beyond the broad generalisation of warming.
There is a real risk of massive biospheric feedbacks that can amplify climate change. Effects that will amplify global warming include loss of sea ice, melting of permafrost, destruction of forests by insect attacks, severe droughts, and uncontrolled fires.
These would reveal current climate projections as far too conservative. The recent report that the surge in climate extremes can be attributed to greenhouse gas pollution lends weight to this idea.
With 7 billion humans we need a reliable Earth system, not a future where extreme weather is the new normal. We urgently need to better understand how the Earth system will respond to the stresses humans are placing on the biosphere. Yet rather than focusing on the challenges sustaining our living one we are fittingly distracted by a dead planet.
There is more coverage of the Mars Curiosity rover here.