By Vince Pinto
Living in southeast Arizona in the Patagonia region is normally a blessing in terms of weather. While a few months may seem like the inside of an oven – think May and June in particular – we experience distinct seasons. Here we can expect over the course of, say, a decade: drought, deluges, floods, gale-force winds, picture-perfect weather, hard freezes, dust storms, and more.
Snow, however, is a rare treat indeed at 4,000 feet. A few dustings, maybe an inch or two, but six inches?! Our early January snow was a rarified way to herald in the new year, allowing all to savor the wintry ambiance and to contemplate the ecological role that the white stuff plays in our region.
Older residents have confirmed that our region – up until the last few decades – received more snow than it currently does. A warmer planet means less snow. This maxim is particularly relevant in southern Arizona, where we can use all the precipitation that nature can muster.
Winter precipitation in any form historically accounts for about 35% of our yearly total here. Monsoon rains fill in most of the remainder. This bimodal moisture is a key factor influencing our world-renowned biodiversity. Two wildflower seasons instead of one, reduced fire hazards, more invertebrates, more seeds, more mammals, etc.
One only has to look at other areas that share our latitude in order to fathom the implications of less snow (and rain) overall. As our close neighbor, albeit a desert away from Patagonia, California holds the most lessons perhaps. In the Golden State they generally receive most of their moisture in winter. This accounts for what seems to be their interminable fire season, which in turn has implications for both biodiversity and human society. Throughout much of the western U.S. there has been a downturn in precipitation over the last few decades, especially in the form of snow. But why is snow so important, as compared to rain?
On a physical and structural level snow often melts slowly into the ground while still blanketing it. This process metes out moisture slowly and deeply to thirsty trees and the plant species that require more than just a superficial dousing. At the same time, any remaining snow cover acts as a sort of lid, serving to retain humidity in the ground that much longer, as opposed to an equivalent amount of rain. Runoff is reduced, while penetration in maximized with snow. Our recent snow event is certainly one reason that I feel we’ll get a fairly spectacular winter/spring wildflower show this year. Snow also helps to replenish streams, rivers, and aquifers – both near to and far from where the snow actually falls.
Further, many species – particularly high elevation species – have adaptations to withstand and thrive with significant winter snow cover. Engelmann Spruce, White Fir, and Douglas Fir all have, to varying degrees, evolved a narrow crown that readily sheds heavy snow. Wider-crowned conifers would suffer structural damage from such a frigid load. Herbaceous plants like Yarrow and Osha grow amidst these conifers, especially in high meadows and burns. There they benefit from the moisture that snow slowly affords them as they remain mostly out of reach of hungry ungulate mouths. The dense fur of some of our mountain-dwelling mammals, such as the Apache Fox Squirrel and American Black Bear, has evolved as a buffer against the snow and cold of winter.
I grew up in Philadelphia where snow was a given in winter. Snow days when school closed, tracking wildlife through a nearby forest, sledding, snowball fights – these were some of my childhood pleasures. For at least a few days this winter we had a chance to revel in these and other snow gifts. Meanwhile, many high elevation species breathed a collective sigh of relief at having gotten a taste of what they so desperately need – snow!
Vincent Pinto and his wife, Claudia, run RAVENS-WAY WILD JOURNEYS, their Nature Adventure & Conservation organization devoted to protect–ing the unique biodiversity of the Sky Islands region.