H. G. Wells dramatically demonstrated how mankind’s future may depend upon the action of small organisms in his War of the Worlds where Martian invaders were ultimately defeated by Earth’s microbes (I do hope I’ve not spoilt the story’s ending for anyone… http://www.answers.com/topic/the-war-of-the-worlds-plot-summary). In a timely reminder of the debt we owe similarly small photoautotrophs, Daniel Boyce et al. (Nature 466: 591–596, 2010) studied oceanic phytoplankton levels extending back to 1899. Examining ocean transparency measurements and in situ chlorophyll observations they estimated the time-dependence of phytoplankton biomass at local, regional and global scales, and concluded that overall global phytoplankton concentration has declined over the past century, with observed declines in eight out of ten ocean regions. Maybe unsurprisingly, they further suggest that these long-term declining trends are related to increasing sea surface temperatures (code for ‘global warming’). This study lends further support to the notion that climate change is contributing to a ‘restructuring of Earth’s ecosystems’. Should we be concerned? Yes! Phytoplankton have a crucial role that belies their tiny size; they generate approximately half of the planet’s production of organic matter and much of the oxygen in our atmosphere. Additionally, they influence climate processes and major biogeochemical cycles, such as the carbon cycle. Sadly, this is the sort of research that gives very little reason to be cheerful.