Effects of Climate Change on Range Forage Production in the San Francisco Bay Area

Abstract

The San Francisco Bay Area in California, USA is a highly heterogeneous region in climate, topography, and habitats, as well as in its political and economic interests. Successful conservation strategies must consider various current and future competing demands for the land, and should pay special attention to livestock grazing, the dominant non-urban land-use. The main objective of this study was to predict changes in rangeland forage production in response to changes in temperature and precipitation projected by downscaled output from global climate models. Daily temperature and precipitation data generated by four climate models were used as input variables for an existing rangeland forage production model (linear regression) for California’s annual rangelands and projected on 244 12 km x 12 km grid cells for eight Bay Area counties. Climate model projections suggest that forage production in Bay Area rangelands may be enhanced by future conditions in most years, at least in terms of peak standing crop. However, the timing of production is as important as its peak, and altered precipitation patterns could mean delayed germination, resulting in shorter growing seasons and longer periods of inadequate forage quality. An increase in the frequency of extremely dry years also increases the uncertainty of forage availability. These shifts in forage production will affect the economic viability and conservation strategies for rangelands in the San Francisco Bay Area.

Microclimate–forage growth linkages across two strongly contrasting precipitation years in a Mediterranean catchment

“…In a dry year, once ample rainfall occurred in late March and early April and soil moisture was easily accessible (Figures 3, 4), more rapid growth occurred on the warmer sites (Figure 9d), though at much lower rates of growth compared with a wet year ( Figure 10). In contrast, a modeling study of climate change impacts on rangeland in the San Francisco Bay Area estimated that by the end of the 21st century, the region will produce 24%-40% more forage, but during seasons that are two weeks shorter (Chaplin-Kramer & George, 2013). For instance, a climate change impact study on California rangeland ecosystem services forecasted decreasing range productivity in the future but did not consider the possible positive effect of warming temperatures-only possible changes in precipitation patterns (Shaw et al, 2011).…”

“…For instance, a climate change impact study on California rangeland ecosystem services forecasted decreasing range productivity in the future but did not consider the possible positive effect of warming temperatures-only possible changes in precipitation patterns (Shaw et al, 2011). In contrast, a modeling study of climate change impacts on rangeland in the San Francisco Bay Area estimated that by the end of the 21st century, the region will produce 24%-40% more forage, but during seasons that are two weeks shorter (Chaplin-Kramer & George, 2013). However, the authors used a growing degree-day calculation for estimating future forage production that ignored the effects of mid-season droughts, which they acknowledged could alter their findings.…”

“…Additionally, these predictions could be used to better understand possible climate change impacts on range production, informing long-term land planning by the livestock industry and local land management agencies. However, model projections for San Francisco Bay Area rangelands indicated that climate change could bring increased productivity but a shorter growing season (Chaplin-Kramer & George, 2013). However, model projections for San Francisco Bay Area rangelands indicated that climate change could bring increased productivity but a shorter growing season (Chaplin-Kramer & George, 2013).…”

“…Climate change is expected to negatively impact southwestern US rangeland production (Reeves, Bagne, & Tanaka, 2017;Reeves, Moreno, Bagne, & Running, 2014), including most of California (Shaw et al, 2011). However, model projections for San Francisco Bay Area rangelands indicated that climate change could bring increased productivity but a shorter growing season (Chaplin-Kramer & George, 2013). Forecasting climate change impacts on California rangelands is inherently difficult given the uncertainty of the global emissions trajectory and the possibility for species distribution shifts (Thorne et al, 2017).…”

Farmers and Climate Change: A Cross-National Comparison of Beliefs and Risk Perceptions in High-Income Countries

“…Several modeling studies suggest that by the later part of this century, changes in temperature and precipitation will adversely impact the yield of several of California's high-value perennial crops (almonds, walnuts, avocados, grapes, etc.) and shorten the growing season for livestock forage in rangelands (Lobell et al 2006;Chaplin-Kramer and George 2013).…”