The Bactra Review: Occasional and eclectic book reviews by Cosma Shalizi   164

Eating the Sun

How Plants Power the Planet

by Oliver Morton

New York: Harper, 2008

Of Heliophagy

I cannot remember the last time I read a popular science book with such enjoyment, or learned so much from it

The first of the book's three part is about how photosynthesis works, at the physical and molecular level. This is relayed by telling the story of how we came to that understanding, and parts of the lives of its discoverers. This embraces a surprisingly long span of the 20th century's golden age of science, and a surprisingly wide range of its sciences: biochemistry, the nuclear physics of isotopes and radioactive decay, the quantum physics of molecular bonding and the interaction of light and electricity, the biophysics of free energy flow through cells and through molecules, crystallography, the molecular biology which let us isolate and manipulate individual enzymes, and so on. (I was pleased to learn how much of the early work was done at Berkeley.) This is a story of discovery, rivalry, insights and false paths, human and biological ingenuity, and ultimately a deep understanding of one of the fundamental processes of life as we know it.

The second part is about the evolution of photosynthesis, and the way organisms carrying it out have interacted with the Earth's climate over the last three-billion-and-change years. This covers everything from the origin of life to plate tectonics to the spread of grasses over the last few million years. Again, much of it is told through stories of discovery and the history of the science. It is necessarily more conjectural than the very settled science of how photosynthesis works, but none the less fascinating for all that.

The third part is about what Morton calls the "climate/carbon crisis". Agriculture already had non-trivial impacts on climate, but our real change began with the Industrial Revolution and the vast growth in consuming fossil fuels. (The second part had a very nice explanation of where those fossil fuels came from.) Huge amounts of carbon compounds, charged with free energy by photosynthesis and then taken out of the biosphere by geological processes over millions of years, are getting burned to release the energy, and returned to the biosphere much faster than they can be processed. The result is that the atmospheric carbon dioxide concentration has already drastically increased over what it was a few centuries ago, and is pretty much bound to keep rising for a long time. Since atmospheric carbon dioxide is good at trapping heat radiated back from the ground, the first-order effect of this is to warm the Earth. The exact effects depend on incredibly complicated and ill-understood feedback processes. (For instance: leaves release water vapor, regulating this through their stomata; what will a warmer atmosphere with more carbon dioxide do to cloud formation above tropical forests, or above plankton blooms?) To take these uncertainties as ground for complacency, though, seems grotesque.

Our global civilization runs at something like 40 terawatts. There is enough fossil fuel to keep going for centuries. (It's doubtful there's enough oil, but there's a lot more coal and natural gas, and quite practical ways of turning them into liquid fuels.) Dumping that much more carbon into the atmosphere, though, is not going to lead to anything good. Tidal and geothermal energy are too localized and small-scale to be global solutions. Nuclear fission looks more attractive when one compares long-lived radioactive waste to long-lived carbon dioxide as a pollutant, but there are very real practical obstacles. All our other options are ultimately solar powered --- winds, rivers, photovoltaic devices, biomass. Morton is very hopeful about the last two, and especially about what real molecular engineering might be able to do in the space intermediate between photovoltaic plates (high efficiency, but also high cost) and naturally-occurring leaves (low efficiency, but they grow).

This is a marvelous book, filled with wonders: I strongly urge you to encounter them for yourself.

xvii + 460 pp., a few black and white diagrams, index, references

Ecology; Evolution; Physics; Popular Science

Paperback, ISBN 978-0-00-716365-6

8 August 2014