I can’t remember who told me this, but it’s emblematic of the responses I get when I tell people I’m a biogeochemist. So, what do I actually do? What is biogeochemistry?
The Global Carbon Cycle, from the IPCC 2013 Working Group I (http://www.climatechange2013.org/)
Biogeochemists study how elements cycle through different parts of the Earth system. Carbon, nitrogen, oxygen, and many other elements are essential for life. Of course, they aren’t just important because of how they’re used by life forms, but also what role they might play in the physical-chemical environment. Carbon, for instance, can be energy for organisms as part of a sugar molecule; a greenhouse gas when in the atmosphere as carbon dioxide; it influences the acidity of waters when dissolved at bicarbonate; or might be stored away for eons as calcium carbonate in limestone rocks. We study how that one element moves through different systems, and interacts with the biology, chemistry and physics of its environment. We do the same for other elements – nitrogen, calcium, oxygen, iron, and plenty of others.
As you might guess from my example, I mostly am interested in carbon. It’s in the food we eat, and the air we breathe. It’s in our water, it’s the energy source for most of our electricity, and the structure for many of the rocks we stand on. It’s important.
Humans are also changing where carbon is found. Hundreds of millions of years ago, during the Carboniferous Period (get it?), wetlands and lowland swamp forests covered vast regions of the continents. Temperatures were warm, oxygen was high, and life was big: this was the age of giant dragonflies and towering tree ferns. The carbon that formed the tree ferns and other plants in these swamps was eventually buried and preserved in sediments. Add time, heat, and pressure – the result is coal. Coal is largely 300 million year old dead plants.
And, as you know, we’re burning that coal. Other fossil fuels – methane/natural gas and oil – have similar histories. Stored away for millions and millions of year, now combusted and turned into CO2.
For now, I won’t get into the science of climate change beyond this: it’s real. It’s not a hoax. And humans are driving it.
The really interesting bit, to me, is that these fossil fuels are not the only potential sources of carbon to the atmosphere. Look at the tropics – how much carbon do you think is stored in the Amazon forests? And how much of that is released when you slash-and-burn it, or during a drought? How much carbon do you think is released when the Indonesian rainforests are replaced by palm oil plantations? Hint: it’s a lot.
Yedoma soils in NE Siberia, with ~30,000 year old plant roots exposed. Photo courtesy of Chris Linder.
Or, go to the poles. Look at the soils. That soil has been frozen for thousands, tens of thousands of years. Since the last ice age, in some cases. Some places, you can look at the soil and see roots and plants that have been preserved for 30,000 years. Many of those soils are peats, sphagnum moss piling on top of each other and compressing and degrading for thousands of years. Maybe you’ve heard of how in Ireland or Scotland, people would burn peat to heat their homes when firewood or coal was scarce. It’s the same idea – compress peat for a few million years, and you’d end up with something very like coal. In fact, the UN classifies peat as a fossil fuel.
Frozen northern soils – permafrost – hold about twice as much carbon as is currently in the atmosphere. Thaw those soils, free them up so that the plants and moss and roots and all the little bits of organic matter can start to rot, and what starts to happen? Where does all that carbon go?
That’s what I want to know.
And I’ll let you know how I’m trying to answer part of that next time!