In spite of the increasing use of local ecological knowledge (LEK) in various environmental studies, few methodological innovations exist to facilitate new uses. This is especially true in studies of environmental change, where standard methods of comparing LEK with scientific knowledge do little to bolster causal claims. Here, I report on a novel approach that uses LEK to formulate manipulative experiments. This interdisciplinary approach exploits LEK's rich historical observations, while employing experimental approaches to disentangle competing hypotheses and to identify underlying mechanisms. This integrated approach produces historically based, mechanistically sound explanations that can be more useful than either LEK or experimental studies alone. I illustrate this approach with recent studies of common reed (Phragmites australis) invasion in salt hay farms.