Late last year National Audubon published Survival by Degrees–389 Bird Species on the Brink, an analysis of the likely effects of climate change on the abundance of North American bird species in the next several decades. The study modeled three levels of temperature increase, corresponding to levels of effort to reduce the discharge of greenhouse gases into the atmosphere. The case with the strongest effects on birds results from the “business as usual” scenario, one with no new efforts. This is the approach practiced by the Trump administration.
The study plugged information on bird distribution into climate models to map where each species might live in a warming climate. The work is detailed enough to show the situation for Yolo County and the Sacramento Valley. With business as usual, Sacramento will become about as warm in spring and summer as Palm Springs is today, and the added heat and drought will kill off our native trees and shrubs. The acreage of oak woodlands in Yolo’s western hills will shrink, and the ribbons of forest along Cache and Putah Creeks are expected to vanish. Major efforts in recent decades to restore forests on floodplains, as on the Cosumnes River and Feather River, probably will be undone. And wildfires are predicted to come so often as to sharply reduce the acreage of chaparral on the Blue Ridge.
These dramatic changes in natural vegetation will necessarily affect birds. Common species, such as California quail, Nuttall’s and acorn woodpecker, California thrasher, yellow-billed magpie, bushtit, orange-crowned warbler (in summer), dark-eyed junco and fox sparrow, will disappear from our area, especially on the valley floor. Birds of the urban forest will also decline, if water becomes too precious to maintain today’s leafy landscaping.
One surprise in the study was a forecast of little change in the amount of wetland and numbers of wetland birds. Though this result appears correct in a strictly physical climate model, political and economic forces will likely come into play. A warming climate will increase the demand for water, but not the supply. Most of the shallow-water and mudflat birding hotspots in Yolo County are evaporation ponds and storm-water detention basins, such as the City of Davis wetland, Woodland’s wastewater treatment plant, and the ponds east of Road 102. Winter-flooded rice fields are most of the rest. All the water that serves those habitats could be easily diverted to other uses. Already, the Davis wastewater treatment plant has converted to a process that eliminated all 235 acres of aeration ponds. The City recognizes that the water thus freed up has numerous possible uses other than bird habitat, and is considering its options.
To access the data that is specific to California, go here. Scroll down to “Vulnerable birds in California” and click on the photos of individual species to see the expected change in their mapped range in California.
In short, a business-as-usual approach to the climate crisis is a disaster in the making for our native birds. Our county and our country deserve better.
Michael Perrone, Conservation Chair, YAS