Trade-offs are not the only constraints affecting the performance and impact of work by living systems. Christina De La Rocha asks us to look at the impact of one of the most fundamental kinds of work on Earth- the work of photosynthesis- from the global perspective provided from biogeochemistry. Starting with the history and basic chemistry of photosynthesis, we see how photosynthesis developed as a work process. We also find that, like many human work processes, it has a choke point, induced by a "working part" that worked just fine when it started but has been unable to change with changing times and conditions. Because this is a crucial part- a critical enzyme- and the changing conditions are the long-term fluctuations in carbon dioxide over the span of life on Earth, this choke point has come to limit photosynthesis and the work of life on Earth. De La Rocha also takes us through the ways in which carbon makes its way through the biogeochemical cycle, and we can see how the work of photosynthesis and the work of the biosphere affect us all.