Role of Long-Term Experiments in Understanding Ecosystem Response to Global Change

For many decades, scientists have sought to understand how ecosystems respond to stresses, especially to those imposed by humans. Already a century-and-a-half ago, for example, Marsh (1864) documented mounting evidence of how human activities were degrading the biosphere and looked for ways of reducing those damages. Now, understanding change has assumed even greater urgency because human stresses on ecosystems, locally and globally, have intensified, driven by growing population and expanding demands (Carpenter et al. 2009; Chapin et al. 2009; Collins and Childers 2014; Gunderson and Folke 2011). In the past, most human effects on ecosystems occurred locally; now, they often extend globally, notably through effects on atmospheric CO₂, which is rapidly increasing, affecting climates around the world (Le Quéré et al. 2015).