If you’ve ever read about carbon storage or sequestration (and if you’ve read my blog before, there’s a good chance you have), have you ever wondered how scientists come up with the numbers they love to throw around? How do we “know” that there are 684-724 petagrams of carbon to a depth of 30 cm in all the soils across the whole wide world? How could anyone possibly know that?
We don’t. And we can’t. But there are those crazy enough to try, and trying essentially boils down to sampling, sampling, sampling, then a whole lot of extrapolating. If you imagine a landscape in which there is a continuous but highly variable distribution of carbon, the only way we’re gong to get any sort of meaningful estimate of the total is to dig a lot of holes. The points you see below represent a lot of holes that I actually helped dig! (I’m one of those crazies). I’ve thrown them up over this topographical surface to give you a sense of just how variable carbon can be across space.
Rather than subject you to a discussion of a ecosystem carbon storage, I’d like to share some pretty pictures I’ve been putting together. I’m attempting to create a model for carbon storage across a roughly 10 km area of forest in northeastern Puerto Rico that is underlain by two bedrock types, contains three distinct forests dominated by different tree species, and has broad gradients in temperature and rainfall across the topographically varied landscape.
Bluer regions represent areas of greater carbon storage while yellower regions store less carbon. Essentially I’ve created an image made of a series of pixels -here, the resolution is coarse enough that you can distinguish individual pixels around the edges. For each pixel, a predicted carbon value has been calculated from a very simple equation that takes bedrock, forest type and elevation into account.
Breaking it down by forest type…
That’s all for now, hopefully I’ll have more and more interesting pictures to show in the future.