Last month I focused this Nature column on our exceptionally dry, La Niña-driven winter. Hold the presses, however, for as you likely know, we received a substantial soaking in mid-February. At long last, the vast, stingy Pacific proffered precipitation. What are the implications of this long-overdue gift for our overall biodiversity and for select species in
particular?
Up until this storm, Santa Cruz County was in a severe drought and, in terms of our aquifers, likely is still overly parched. No one storm generally delivers sufficient moisture to provide complete succor from monumental drought. This rain was mostly an incessant downpour, soaking quite deeply into our parched soils. At the very least our level of fire danger went from extreme to low for a while.
Plants with shallow roots are immediate beneficiaries of winter soakers. This includes ocotillos whose roots readily absorb much-needed soil moisture, translating in warmer counties of southern Arizona into a flush of green, ephemeral leaves. Our ocotillos likely will forgo frost-sensitive leaves until at least April. Various species of cacti have similarly evolved more superficial roots to take advantage of even meager rains. Mid-storm I observed what I have also witnessed over the years – namely, that many cacti perk up during a rain event. This quick response allows them to literally weather the many desiccated vagaries of our southern Arizona climate. Chollas, fishhook barrel cactus, and prickly pears are among the winners in this particular rain lottery.
Trees, too, need a deep soaking any time of year and will generally recover swiftly from the effects of drought. Maybe now our drought-deciduous oaks can maintain the majority of their leaves until the monsoons.
By far the biggest observable effect on plants may well be a just-in-the-nick-of-time emergence of some spring wildflowers. Normally I would deem such a mid or late winter rain too tardy to affect such a wildflower emergence. This rain, however, felt like a game-changer. It was so much – about 2 inches plus – and still going as I write – that I cannot imagine a scenario where wildflowers as a whole don’t respond to some degree. It’s a bit of
a no-brainer that wildflowers can and will swiftly bloom in a desert environment. Locally, though, we live at higher, cooler, and wetter elevations than true desert climes. Thus, our spring wildflowers tend to be more rain finicky than the hit and run response easily observed in the Sonoran and other deserts. Even the same species observed in high and low elevations, such as Mexican poppy, flower much more readily in the latter given the same precipitation.
This winter has seen depressed populations of many rodents, lizards, and butterflies among others, thus the rain might indirectly benefit these species as well. A solid plant response through the remainder of winter and into spring certainly can help provide some green forage for herbivores, seeds for granivores, flowers for nectarivorous species, insects for predators, and ultimately dead plant material for detritivores. How much relief from depauperate drought conditions various species receive should begin to unfold as the PRT goes to press.
I’ll end by hedging my bet, as I’ve learned one thing about our weather over the years – the results of the rain lottery are wildly and wonderfully unpredictable. Maybe that’s why I love participating in these fascinating ecological forecasts and their impact on the Sky Islands ecosystems!
Vincent Pinto and his wife, Claudia, run RAVENS -WAY WILD JOURNEYS, their Nature Adventure & Conservation organization devoted to protecting the unique biodiversity of the Sky Islands region. Visit: www.ravensnatureschool.org