As we have just experienced an intense and prolonged drought, a team of scientists has just published in Nature Climate Change Letters an analysis of impacts in the Carrizo Plain. They quantified the responses of 423 species of plants, arthropods, birds, reptiles and mammals to California’s drought of 2012–2015—the driest period in the past 1,200 years for this global biodiversity hotspot.
The article by Prugh and others was published in Nature Climate Change Letters “Ecological winners and losers of extreme drought in California” August 20th, 2018 The report states that plants were most responsive to one-year water deficits, whereas vertebrates responded to longer-term deficits, and extended drought had the greatest impact on carnivorous animals. Perhaps surprisingly, locally rare species were more likely to increase in numbers and abundant species were more likely to decline in response to drought, and this effect was remarkably consistent across taxa and drought durations.
Of the mammals, California ground squirrel, San Joaquin kit fox and Giant kangaroo rat fared badly, while Southern grasshopper mouse and Short-nosed kangaroo rat were successful. For birds, barn owls and western meadowlarks declined, while killdeer and roadrunner populations remained stable. The rare Blunt-nosed leopard lizard suffered, but the coast horned lizard and side-blotched lizard were little affected. Spiders and scorpions declined, but certain beetles did well.
As was obvious to most people, nearly all plants were impacted, but certain hardy species such as Calandrinia were successful in the absence of competition. The study concludes that while extreme droughts can produce substantial short-term declines in the abundance and diversity of species, these disturbances may play a vital role in the long-term maintenance of biodiversity by inducing periodic die-offs of dominant species and subsequent opportunities for rare, yet fast-growing, species.
This study is especially useful as climate change projections indicate that extreme, extended droughts will become more common, as well as the maximum summer temperature, and the duration, intensity and timing of the rainy season.
As far as SLO Chapter is concerned, I am hoping we can work with Cal Poly, BLM, and the Friends of the Carrizo Plain to institute a long term monitoring program in which we can collect photographic and quantitative data on the conditions at different parts of the greater Carrizo Plain. There are already ongoing experiments in which exclosures are used to exclude
larger animals and, in an inner fence, rodents from the grasslands, but I don’t know of any broad vegetation assessments apart from the CNPS-generated vegetation map which was a snapshot of conditions, and is governed by the dominant plants rather that the complete population.
I would propose that this spring, we get together a group to select a series of areas that will be linked to GPS coordinates, and that the sites would be revisited and photographed (and possibly inventoried) a couple of times per year, and over many years. I am intending to meet with faculty at Cal Poly to see if they would see a way to direct a series of student projects in a similar effort.