Restoration sites on the Californian coast have different ecological histories that can influence restoration success

Abstract

For each restoration project, it is essential to define a reference ecosystem towards which ecological restoration aims. Historical information may be useful in the construction of the reference model and in finding out about the type and degree of disturbances that have caused degradation on the site, as legacies of past human land-uses have been shown to be major determinants of vegetation and plant diversity even in the very long term. The aim of this paper is the retrace the history of three sites where restoration protocols were tested, to better apprehend the potential reference ecosystems as well as the disturbances that degraded them. To do so, we first compiled information on the reference ecosystems at the landscape scale. Then, we compiled historical and agricultural information at the scale of the sites from local historical documents, historical reviews and aerial photographs. The three sites most likely were grasslands or oak savannas before European settlement. Grasslands used to cover 8.9 million ha in California. They were species-rich grasslands managed with fire by the native people and grazed by native ungulates. Early settlers introduced cattle grazing and changed fire regimes. Later on, many grasslands were converted to cultivation. All three sites were used for ranching and sometimes overgrazed. At least two of them were cultivated, probably leading to restoration being harder there, as plowing eliminates perennial species, destroys the seedbank, changes soil characteristics.