San Diego County Ecosystems: The Ecological Impacts of Climate Change on a Biodiversity Hotspot
KEY POINTS • San Diego County is part of a biologically diverse and unique landscape that will be impacted in multifold ways due to current and future climatic variability.
• This assessment of the state of the science, is critical to understanding the vulnerability of systems, and allowing partners to take stock of the state of knowledge about potential climate impacts at the regional level. • Climate warming superimposed upon the pronounced spatially-varying temperature in the San Diego region will likely be associated with range shifts for many species resulting in novel community assemblages and biotic interactions. • More frequent and more intense heat waves may disproportionately affect younger age classes and reduce reproductive and survival rates of species sensitive to temperature extremes. Warming temperatures may also create phenological mismatches. • The region’s precipitation regime is projected to become more variable with more dry days and more dry years. However, the few extremely heavy precipitation events, increased over historical levels could result in increased flooding and occasional wet years.
• Drought may occur more frequently due to increased occurrence of dry days and could
intensify because of warmer temperatures. Since drought disproportionately affects some species, these projected changes may cause structural changes to ecosystems.
• Annually, the occurrence of Santa Ana winds during increasingly dry fall months would create ideal fire conditions. Longer dry spells and decreased precipitation in fall may extend fire season into the winter, increasing the risk of Santa Ana wind-driven fires. Regardless of climatic shifts, people will remain the major driver of fires in San Diego.
• Coastal low clouds and fog buffer warming and drying along the coast through shading
and cooling. Although these marine stratus clouds will remain a presence, future changes in this phenomenon are uncertain, so the degree to which this will ameliorate the impacts of warming and drying is unknown.
Photo of San Miguel Mountain by Joanna Gilkeson/USFWS
