From Karban and Huntzinger’s How to Do Ecology: A Concise Handbook:

Since manipulative experiments in ecology today are almost always conducted at spatial and temporal scales smaller than our ideal, it is worth considering what effect this has on our worldview. Small-scale experiments have led us as a group to believe in local determinism, that is, that the processes we can manipulate on a small scale mold the patterns that occur on larger scales. However, this view is likely to be simplistic when we look at real communities. For example, local processes such as competition and predation tend to reduce species diversity, while larger-scale regional processes tend to increase diversity through movement and speciation. Our view of local determinism can be tested by placing a barrier around a local area and observing whether species persist. In most cases, they don’t. Even the largest parks such as Yellowstone and the Serengeti are too small to maintain a full complement of species over the long term … An appreciation for larger-scale processes such as the interactions with other organisms in the species’ range and interactions that occurred in the past can help our thinking, although these processes are difficult to study experimentally. [Citations removed]