Moving from an experiment-dominated to an observation-dominated era in global change impact research on vegetation

In 1992, at the start of the senior author's career as a plant ecologist, climate change was perceived as something that would occur in future, and efforts were focussed on predicting what the impacts of those future changes on ecosystems would be, using the tools of manipulative experiments and models. This was still largely the case a decade later, at the start of the more junior author's career in the same field, although observations of impacts resulting from climate change that had already occurred had become more common. More than two decades on, we are deep into the trajectory of climate change, with atmospheric CO₂ having reached 50% above the pre-industrial average, and other drivers significantly beyond their 20th-century baselines. We therefore argue that we must rethink the way we conduct experiments. We will likely move from an experiment- to an observation-dominated era of climate change impact research. This transition could be more explicitly considered and may require adjustments in research policy and funding. We present a practical guide to plan experiments in this new era of researching global change impacts on plants.