OK, the rain is officially taunting us. If you haven’t yet caught wind of it, this is a La Niña (“the little girl” in Spanish) year. Unlike “normal” years of winter precipitation and abundant years proffered by El Niño, you can expect very little in the way of wetness until July…maybe. Personally, it has taken me until this
very year to embrace this cycle of nature, including all its potentially challenging consequences for Arizona and our unique Sky Islands.
La Niña is a cooling of the surface waters in the eastern central Pacific Ocean that generally spawns less precipitation in the southern North America and more in our northern states and Canada. El Niño, a warming of Pacific waters, has the polar opposite
effect, sometimes deluging southern Arizona, while plunging Seattle into a drought. Given our current dearth of rain and snow, many challenging ecological and human dramas play out during and in the aftermath of La Niña.
Lacking sufficient moisture, some perennial plants end up dying. Anything from grasses to shrubs to trees can succumb to the drought imposed by La Niña. Some will expire soon, while others try to ride out the tough times. Even the latter may partially or fully die back if the monsoons are likewise overly stingy. Already, I have noticed many of our otherwise
evergreen oaks beginning to yellow and drop leaves. These drought deciduous oaks have evolved the ability to lose some or all of their leaves in response to desiccated times. No leaves, no respiration via their stomata, the pores that give off water vapor. So, get ready for a legion of dead-looking oaks.
Various animals may be stressed as well by the sere landscape. Already, it seems that small
mammal, reptile, and bird populations are somewhat-to-very down in numbers. Taking the broad view, this is all part of the cycles of nature that ultimately come back to a fluid equilibrium. In the short-term, however, things can be taxing.
What then, you may ask, is so good about La Niña? Just to the southwest of us looms the
hyper-diverse Sea of Cortez. Since cooling oceanic waters equate to more productivity, the Sea is a winner in this droughty winter. More nutrients means more plankton, and hence increased numbers of many marine species from invertebrates to fish to birds. Closer to home, we are collectively likely to experience more visitors from the states frozen and/or inundated by this winter’s La Niña. Tourism is one of the mainstays of our economy in southern Arizona, so roll out the welcome mat. One of biggest payoffs of La Niña is our
picture-perfect winter weather and this year, thus far, has been the poster child for a warm getaway to beat the winter blues.
The vagaries of short-term weather changes ultimately force various species to evolve and become more resilient. While the drought indeed kills various native species, it also knocks down the populations of nonnative grasses, such as Natal grass. Many grasshopper species seem to thrive on the drought-sprinkle-drought cycle we are currently experiencing. While some of these can be minor or major garden pests, they also provide beauty, diversity, and key food components in the diets of such species as grasshopper mice, American kestrel, and loggerhead shrike. Warmer weather can also produce more winter butterflies in February, as you may witness in and near Patagonia Lake.
Most profound for me is the stark contrast that La Niña provides versus wetter, more abundant times. It is the yin to the yang of greener years. In a world already dealing with
climate change La Niña might well seem like piling on the stress in Arizona. Perhaps, but hope springs eternal. Just wait…rain might be right around the corner!
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