Experiments to confront the environmental extremes of climate change

Extreme climate conditions can dramatically alter ecosystems and are expected to become more common in thefuture; however, our understanding of species and ecosystem responses to extreme conditions is limited. Wemust meet this challenge by designing experiments that cover broad ranges of environmental stress, extendingto levels well beyond those observed currently. Such experiments are important because they can identify phys-iological, community, and biogeochemical thresholds, and improve our understanding of mechanistic ecologi-cal responses to climate extremes. Although natural environmental gradients can be used to observe a range ofecological responses, manipulation experiments – including those that impose drought and heat gradients – arenecessary to induce variation beyond common limits. Importantly, manipulation experiments allow for deter-mination of the cause and effect of species and ecosystem threshold responses. We present a rationale and rec-ommendations for conducting extreme experiments that extend beyond the historical and even the predictedranges of environmental conditions.