The Test of Time: Using Historical Methods to Assess Models of Ecological Change on California’s Hardwood Rangelands

Abstract

Geographers and environmental scientists use conceptual models to understand ecological processes and support management decisions. Most of these models are based on short-term experiments and field observations, which might not account for longer term forces that shape ecosystems over decades to centuries. How can scholars use historical sources and methods to improve conceptual models of ecological change? In this article, we present the results of a study that employed methods from environmental history and historical geography to assess three conceptual models that researchers have used to study ecological changes on California’s hardwood rangelands: the succession and climax, state and transition, and cyclical replacement models. The succession and climax model fared poorly at all spatial scales. The historical record contained substantial evidence to support the predictions of the state and transition model at the small spatial scale of the plot or field (0.1–100 ha) and the very large spatial scale of the hardwood rangeland bioregion (4 million ha). The cyclical replacement model performed well at the intermediate scale of the landscape or typical cattle ranch (100–10,000 ha). Historical data and methods hold considerable untapped potential for assessing, building on, and improving conceptual models of ecological change in geography and the environmental sciences.