In this talk, I will introduce the idea that ecosystems located near glaciers can serve as natural laboratories for global change biology and paleoclimate studies. This is because they have experienced climate changes that were amplified by nearby ice-margin fluctuations. I will report on results from one of these natural experiments in the old-growth temperate rainforest near La Perouse Glacier in Southeast Alaska. We used dendrochronology to observe how tree growth responded to a shift from “normal” to accentuated rates of summer temperature change that occurred in the mid 1800s. As trees became more climate stressed, five species that had grown in unison for centuries suddenly shifted to a more diversified growth pattern. This shift in growth patterns helped attenuate forest-wide growth declines and stabilize the forest ecosystem during stressful climate periods. Results suggest that accelerated climate change can push forest communities through a series of critical transitions between stable states of climate sensitivity. Over millennia of climate changes, tree species and phenotypes may be ecologically sorted into forest communities that are capable of absorbing moderate levels of climate stress by activating a diverse portfolio of growth responses. This response mechanism may be one tool that can help maintain ecosystem services in our more turbulent climate future.