Biological productivity in a number of ocean regions appears to be at least partly limited by the availability of iron. Any reduction in the present-day aeolian iron supply to the open ocean is therefore likely to result in further limitation of productivity. The stabilization of soils for the purpose of carbon sequestration could give rise to such an effect. With the aid of a global carbon cycle model, we show that the effectiveness of carbon removal from the atmosphere by sequestration on land will be diminished as a result of a reduction of up to 9% in the rate of anthropogenic CO2 uptake by the ocean. This interconnectedness, both within the `natural' system and in relation to human activities, highlights the importance of analyzing global change within an integrated ‘Earth system’ framework.