Carbon cycling, storage and sequestration

Chapter Overview

No biogeochemical cycle receives more attention these days than the carbon cycle. In this module, we make no attempt to cover the entire carbon cycle or all the issues related to global warming. Instead we focus primarily on the issues associated with mitigating the effects of human alterations of this cycle.

Our students come to us generally convinced that conservation is the primary route to solving the modern carbon dillemma. However, "back of the envelop" calculations quickly show that the magnitude of conservation efforts must be large, and the consequences for developing countries profound, if we rely entirely on conservation to limit the effects of increased levels of carbon dioxide in the atmosphere.

What about various sequestration strategies? We look first at the question of whether fertilizing the oceans with iron is a viable strategy to mitigate our consumption of reduced carbon. We consider why organisms need iron and why it might act as a limiting nutrient in some environments. This discussion connects with the previous section on nutrients in lakes, but now the scales are smaller - we explicitly look at the molecular level reasons organisms need iron and the concentrations of trace metals in the ocean are truly trace and the degree of uncertainty larger.

In this section of the course we begin to develop another major theme of the course and of environmental science -- another skill that the environmental scientist or environmental practioner must have -- familiarity with and an understanding of uncertainty.

The lab module we have developed for this section of the course asks students to build a model, using Stella, to estimate the effect of iron fertilization on atmospheric carbon dioxide levels. Scientists do not know what the effects of large-scale iron fertilization would be. Gaps still remain in our understanding of carbon cycling between the deep and surface oceans. However students can try different assumptions and see how they play out in a simple model of oceanic biogeochemistry.