Readers may recall the “Notes from the hillside” articles I wrote for The Paintbrush newsletter during the years I carried out a weekly survey of native flowers on the hillside above our house in western Pasadena. The survey extended over six years, from January 2013 to September 2019. It covered a broad spectrum of good and less-good flowering years, good rainfall and not-so-good rainfall. Regardless of annual conditions, there was always something interesting to see. The annual floristic cycle was a treat to watch every year.
Having lived here since the mid-1980s, I have rainfall records covering the period 1987 through 2021. The chart above shows the annual rainfall totals for these 35 years of measurements. (Note that this record uses July-to-June years, with the named year being the second six months of each twelve-month period. This scheme fits well with our winter rainfall pattern.)
With this chart it’s difficult to visualize trends over the years because annual totals vary so greatly from year to year, typically with a big spike approximately every five years. To help in bringing out the trend, the red line on the chart shows a simple 7-year average, which over this period has gone down from 22 to 14 inches of rain, about 35% in 27 years, with an especially noticeable reduction in the past 5 to 10 years.
A single parameter such as rainfall does not fully characterize changing climate, of course, but it does imply that diminishing rainfall may directly impact the native vegetation. On these hillsides we had noticeably fewer spring flowers this year. But an observation I found particularly distressing this year is the state of the one specimen of coastal wood fern that I have found on these hillsides. It has always looked fully alive throughout great and not-so-great years, although with varying amounts of greenery. However, this year by August (the first month when I looked at it), the fronds of the fern had all collapsed. At the time of this writing (mid October) they were mostly withered to almost nothing, with just a little green here and there. The coming winter rains will hopefully revive this beautiful plant.
There are other changes, too. For example, the many self-sown monkey flowers in the semi-natural parts of our extensive back yard did not give us the mid-spring mass flowering of previous years.
I find myself wondering whether, if the rainfall trend continues, we may see permanent changes. There might even be changes that are difficult to reverse when and if better regular rainfall resumes.
Similar situations exist elsewhere in the world. I was reminded of this by an article about western South Africa discussing what appear to be permanent changes. Regarding that country’s mid-west coast, the article states: “It is not just a poor showing of annuals and bulbs that has us worried. That would be expected in any dry year. More disturbingly, it is the unprecedented loss of vast numbers of long-lived perennials — succulents, shrubs and trees — that we and most others thought would survive even the worst drought. This loss has fundamentally altered the look, feel, smell, and probably also the ecological functioning and viability of the entire region.” (Nick Helme and Ute Schmiedel, “Namaqualand nightmare,” in Veld & Flora, June 2020, Botanical Society of South Africa.) The region has similarities to our part of southern California, and is home to the largest concentration of succulents in the world. And there are wildflowers, which were spectacular when I last visited the area 12 years ago. Hopefully we’ll not experience such a major level of change here.