By Amanda Mascarelli
The Southwest is the most unrelentingly hot and dry region in the United States. Future predictions—of increased fires, drought and floods—border on biblical. Gregg Garfin is a climatologist at the University of Arizona in Tucson and a coordinating lead author for the Southwest-region chapter of the National Climate Assessment, released in May. In this Q&A, he reflects on the dire situation, his “apocaloptimist” nature and the bright spots he sees on the horizon.
Shaped by scouring winds and a dearth of water, the Southwestern landscape has been winnowed down to a bare-bones composition of species adapted to its harsh conditions. Still some of them may not be able to withstand what climate change will bring.
I grew up surrounded by sagebrush and Juniper trees, steep sandstone precipices jutting above the horizon, in a remote corner of northwestern New Mexico. The landscape is disarmingly barren and vast, pocked with oil fields and gas derricks seesawing in the distance, and hemmed in by a patchwork of American Indian reservations.
It’s not easy to wrap one’s mind around how this region is being altered by the changing climate. Yet the people living here face unprecedented challenges in the coming decades: the population is expected to swell to 94 million—a 68 percent increase—and, by 2050, agricultural traditions and energy production will be strained by a dwindling water supply. Wildfires and floods are becoming more severe and frequent, while snowpack is shrinking—accelerated by increasing heat and drought.
The National Climate Assessment is pretty bleak. What aspects of it were most eye opening?
Gregg Garfin: The report speaks to both sides of my apocaloptimist nature. That is, somebody who knows that the future looks dismal if we continue on the current path, but has faith in our ability to innovate and collaborate our way to solutions. The projections are dire, but the assessment brought together more region-specific data as well as examples of adaptation strategies.
Something I find interesting is our growing understanding of how “atmospheric rivers” formed California’s record-setting floods. The common name is the “Pineapple Express”; it’s a stream of moisture emanating from the tropics into our middle-latitude region—as far inland as Utah and New Mexico—and dump a lot of moisture in a relatively short period of time. Atmospheric rivers can cause these rain-on-top-of-snow storms that would lead to big floods, the kind of floods where you can imagine Sacramento under water. That’s a big deal.
What can the Southwest expect over the coming decades?
We’re expecting part of the Southwest to be warmer and drier—for most of Arizona and New Mexico, climate models project the number of consecutive dry days to increase by 9 to 12 days in the latter part of this century.
And we expect these extremes to get more extreme: During the wet periods—even if we don’t receive any more or less precipitation—it will show up in a shorter period of time. And then we’ll have longer dry periods in between.
The harbingers of that might be something like last fall’s extreme precipitation (that led to the Boulder flood) in Colorado.
It seems ironic that in the face of warming and intense drought, we are hit with such extreme floods. What is the relationship?
The precipitation in Boulder on September 13, 2013, was about a third more than anything previously in the historic record. That’s along the lines of what we might expect in the coming decades. What people often don’t realize is that as you heat up the atmosphere, it can hold more moisture. Therefore the types of storms we are likely to see are more like those from towering summer thunderclouds – the moisture is going much higher in the atmosphere, and the storms are much more intense.
So if temperatures increase on the order of 5 degrees Celsius or more as we’re expecting in the Southwest by the end of the century (based on current emissions), we would expect the moisture-holding capacity of the atmosphere to increase 35-40%. That’s a big amount.
For the Southwest, it’s the end-of-the-century time-frame, 2070s-2100, when we would expect those intense precipitation events to occur twice as frequently. A 100-year event would now occur more like every 50 years.
What Southwestern towns are most at risk of running out of water in the foreseeable future?
Las Vegas, Nevada is one. The Southern Nevada Water Authority is among the most progressive water management agencies on issues around climate and drought, and it’s because their water supply is so vulnerable – they depend almost exclusively on drawing water from Lake Mead. They’ve been very creative and very aggressive about trying to develop alternative supplies. For instance, they’re banking part of their Colorado River water supply underground in Arizona so they can withdraw it at a later date. They’re well known for paying people to rip up their lawns and replace them with xeriscaping for water-conservation purposes. They are acquiring groundwater rights in rural Nevada to augment their water supplies, which brings up fears in the rural West, and some opposition.
Also, there’s a giant groundwater aquifer, known as the Ogallala Aquifer, which stretches through eight states, from South Dakota and Nebraska through Kansas, Oklahoma and into New Mexico. We know that we’re over-pumping that. And it may well be that agriculture in that area of Northeastern New Mexico is just not sustainable when relying on major groundwater irrigation. That’s a place that definitely is vulnerable.
In a brutally dry climate, it’s hard to perceive these changes. In fact, many people fail to have a sense of urgency around the changing climate. What changes do you see in the Southwest?
It is difficult to discern these kinds of changes in the Southwest region because our precipitation is highly variable from year to year. We have wet and dry episodes that last years to decades.
One of the big changes is the occurrence of invasive species (not caused by climate change, but likely will be exacerbated by it). In the southern part of the Southwest deserts, invasive grasses are changing the ecology of the low desert, making the vegetation more prone to fire than native species were. For example, in the Colorado Plateau, cheatgrass has been taking over. When cheatgrass dries out, it’s just a tinderbox waiting for an ignition to set off a fire across large swathes of the landscape.
We also think that some desert species, even those adapted to hot, dry conditions, are reaching the limits of their physiological tolerance. Some research indicates that Joshua trees in California just won’t be able to survive in the areas that they currently populate.
Intense wildfires will be the new norm, according to projections from the NCA. How do you respond when asked whether a given fire is directly or indirectly attributable to climate change?
We can’t get away from climate change being a contributor to the characteristics of wildfire potential and fire danger. The relationship between temperature and fire impact is pretty strong.
Anthony Westerling, an expert on the links between climate change and wildfires at the University of California in Merced, points out time and again that as temperatures go up, degree by degree, the number of acres burned goes up exponentially. You can have a dry year. But if you have those hotter temperatures, it really feeds back strongly to the fire activity.
The report emphasizes impacts to native nations and people living in Southwestern border cities. I just visited El Paso, Texas, where the poverty on the Mexican side of the Rio Grande is stark. How will things change for people living there?
Large urban areas like Juarez, Tijuana, Nogales and others will experience increased temperature as well as the temperature amplification that comes with roads, houses and buildings that absorb more heat and retain that heat into the night—the so-called urban heat island effect. The average temperature in the cities can be 5-7 degrees Fahrenheit higher than the average temperature out in the desert.
These border cities generally are characterized by having higher levels of poverty, lower socioeconomic status, and in some cases poorer infrastructure. So then there’s all sorts of cascade effects if, for example, people can’t afford air conditioning or their infrastructure can’t withstand intense precipitation events.
Native American tribes are finding it harder to grow traditional tribal foods like corn. And as drought has worsened, plants that stabilize sand dunes are not surviving, leading to the migration of sand dunes into residential areas, and causing housing and transportation problems. There have also been reports of springs, important for livestock and wildlife, drying up on Native American land.
In the Southwest and the Rocky Mountains, which landscapes will look very different in 50 years?
Forests, rangelands and even riparian areas could look very different. We’ve already seen the shrub encroachment and encroachment by invasive species. So our rangelands have already been changing. We would expect those changes to continue and maybe accelerate.
Some of our riparian species, like sycamores and cottonwoods, might not be able to survive. I’ve heard Tom Whitham, an ecologist from Northern Arizona University, talk about how an individual riparian tree can support something like 300 species, including birds, insects, lizards. In terms of the food web, if we lose the tree, there could be a whole cascade of effects.
Which forests in the U.S. are most in trouble?
Ponderosa Pine forests—which can withstand low-intensity fires that remove undergrowth— have suffered really severe fires. In some of these areas, I’ve heard ecologists predict that in my children’s lifetime, we probably won’t see a Ponderosa Pine forest here.
Since the era of fire suppression, the forests have become much more jammed up with vegetation. A longer snow-free season and hotter temperatures to dry out the fuels has led to more severe fires, the kind that completely wipe out vegetation (such as the 2011 Las Conchas fire in the Jemez Mountains, the largest wildfire in New Mexico’s history). In some places these fires cauterize the soil, leaving behind a water-repellant landscape that is prone to erosion and prevents vegetation from taking hold.
As well, tree die-off, due to the combination of heat, drought, and bark beetle infestation, is occurring in Ponderosa Pine forests, but also in Piñon-Juniper forests. The trees are under tremendous drought stress, and the bark beetles have a longer breeding season and are therefore more effective at knocking them out.
Do you see bright spots on the horizon?
There are two things that we need to do: Reduce emissions of heat-trapping gases, the root cause of climate change, and adjust to the projected effects of climate change. Even with our best efforts to reduce emissions, there will be continued increases in temperature due to the longevity of heat-trapping gases in the atmosphere.
As individuals, we all have choices we can make in terms of transportation, home heating and cooling efficiency, and food that can lower emissions. But it’s the community responses that are encouraging.
Native tribes and nations, even given all of the vulnerabilities they face, have been really engaged in planning for climate change and also taking advantage of initiatives to invest in renewable energy, such as solar.
More of our cities are doing climate change planning as well. Coastal communities in California have been planning for sea-level rise. At neighborhood scales, there are investments in smart grids that can better incorporate solar and windpower into the power grid. Cities are also investing in cooling shelters. Tucson and Phoenix are planting trees. The Albuquerque, New Mexico metro region is in the midst of a climate adaptation planning process.
Things are dire. Some folks might say it’s too little too late, or that we’re not doing enough. But I couldn’t get out of bed in the morning if I wasn’t hearing about more and more initiatives where we’re actually doing something.
Edited by Virginia Gewin