Local Biodiversity Hotspots at Risk From Climate Warming
Phainopepla – Male ©Ann Brice
A new study out of UC Davis highlights the biological richness of the western hill country of Yolo County and nearby areas and the grave threats to its continued existence posed by a warming and drying climate and related increases in wildfires.
Our state has more kinds of native plants, animals and vegetation types than any other state or most countries, and a remarkably large number of plant species that occur nowhere else. The only places in the world with more kinds of plants are undisturbed tropical forests.
Particular parts of the state have especially high plant diversity, which is a foundation of animal species diversity as well. The study noted fifteen well-known areas of high diversity in California, which it called regional hotspots. These include the “Blue Ridge-Berryessa” and “inner Coast Range” hotspots, the one in western Yolo and eastern Napa County and the other just to the north of us, in Colusa County.
The authors predicted the likely changes to plant diversity in the hotspots as our climate continues to warm in the next forty to sixty years. The news is grim. The Yolo/Napa hotspot vanishes and the inner Coast Range hotspot nearly does so. More generally, plant species of familiar and important local bird habitat types – oak woodland, oak savannah and native grassland – all show big declines. Although some northern California hotspots are expected to migrate to Oregon along with their plants, our local ones do not. The largest driver of these changes is warming temperatures, which in turn cause more severe droughts in vegetation types that are water-limited to begin with. Droughts have the further effect of encouraging larger, and more frequent and severe, wildfires. And we have all recently seen what large wildfires do to the vegetation of the inner Coast Range. Trees die and chaparral shrubs burn too often to produce enough seeds to allow for their regeneration (as discussed in my January 2024 article).
What can we do to help? First, conservation of biodiversity under climate change is the centerpiece of the state’s “30 x 30” initiative. It is part of an international movement to conserve 30% of our lands and coastal waters by 2030. In short, the aims are to conserve habitats representing the full diversity of California’s ecosystems, targeting locations that, ideally, will (a) remain suitable under climate warming and thus serve as refuges, and (b) provide corridors for plant and animal migration. Parts of our two local biodiversity hotspots are considered conserved as part of the 30 x 30 effort, including Bobcat Ranch.
Second, and obviously, nations everywhere must work to reduce fossil fuel use and greenhouse gas emissions.
Third, new ways to manage fires are badly needed. The topic is too big for this article, but the essence is that more than a century of intentional fire suppression has led to huge accumulations of live and dead fuel, plus ecosystem damage from the fire-fighting methods and equipment themselves.
Fire-fighting agencies have agreed to use so-called prescribed burns, that is, controlled, intentional fires, to reduce fuel loads and return forests to a more natural state. But old habits die hard, and fire suppression is mostly still with us. In any case, prescribed burning is only practical near human settlements and with decent roads, both of which are largely lacking in our nearby hotspots.
The study, “Climate change and California’s terrestrial biodiversity”, is in PNAS, a scientific journal. The lead author, Susan Harrison, is an avid local birder. To learn about the 30 x 30 plan, visit Californianature.ca.gov/pages/ca-nature. The website has a “conservation areas explorer” feature that maps areas that are considered conserved under the initiative.
— Michael Perrone, Conservation Chair