Background/Question/Methods   Climate change has the potential to markedly alter the species composition of grasslands as well as the quantity and quality of grass, which might have important consequences for their ability to support grazers. Yet, little is known about how climate change might affect grazers in North America. Climate change experiments are not conducted at large enough scales to encompass grazers, long-term data sets on grazer performance are rare, and geographic patterns of grazer performance has not been quantified. To better understand how climate change is likely to alter the performance of grazers, I focus on patterns from monitoring of interannual patterns of weight gain and calving rate in bison and continental-scale patterns of forage quality.

Results/Conclusions   The lessons that can be learned from these data include: 1) the quality of grass is just as important to consider as the quantity of grass; 2) grass quality is more a constrain on grazer performance in humid than xeric grasslands, 3) changes in the timing of precipitation is just as important as changes in the amount of precipitation; 4) geographic patterns show that warming and/or precipitation declines will decrease forage quality, which would be expensive to mitigate. Important future considerations include monitoring of grazer performance to understand coupling of climate-nutrition-performance cascades at the continental scale, the role of the timing of fire in alleviating quality crunches, and a better understanding of how climate impacts forage quality through changes in N cycling and plant C gain and allocation.