Historic and contemporary landcover, urban areas and protected areas as a framework for regional conservation planning

Background/Question/Methods: Globally, over 50% of all humans now live in urban areas, and to these 3.3 billion are projected an additional 1.75 billion people by 2030. The process of urbanization transforms natural landscapes with irreversible impacts to biodiversity, ecosystem structure and ecological processes. The rapid growth of cities has led to increasing research about their impacts to natural ecosystems and on the need to establish reserves for natural vegetation and native species within expanding urban areas. Conservation planning at the metropolitan regional level can be informed if the historic trajectory of urban growth, conservation lands, and land cover change can be quantified, because these trends set the context to evaluate conservation success to date. We examined these measures of landscape change for an 8800 km² section of the San Francisco Bay Area for change between the 1930s and 2010. We developed two historic datasets, the Wieslander Vegetation Type Maps for natural vegetation and urban extent, and the date of establishment of protected areas. This permitted quantification in the trends of land cover conversion and protection.

Results/Conclusions: Agriculture and ranched grasslands showed by far the biggest decline, going from 5218 to 3134km². Urban areas expanded over 454% to 2144 km². Among natural vegetation types, Blue Oak Habitats and Coastal Salt Marsh declined by 32 and 61% of their historic extents, respectively. However, some native land cover types improved, including coast oak woodlands, redwood forests, and Douglas fir forests, at 5.4%, 56.7% and 217% (to 176 km²), respectively. By 1940, there were 400.4 km² protected, with the largest two native vegetation types protected being grasslands (45.7km²) and chaparral (42.06km²). Currently there are 2961km² protected, and the two best represented types are grasslands (738.9km²) and coastal woodland (310.4km²). The types that have lost extent and are poorly represented in current reserves represent highly important habitats to increase in the protected areas network.