Will Joshua Tree National Park become Creosote Bush National Park?

This story appeared in the September 2013 issue of Desert Report.

Throughout time, the earth’s climate has changed. Factors pushing climates to be either cooler or warmer include orbital shifts bringing the earth closer or farther from the sun, changes in solar output, changes in the position of the continents, and changes in atmospheric carbon dioxide (CO2) and methane. The greenhouse effect, resulting from atmospheric CO2 and methane, has been well established for nearly a century. The signatures of past climate changes can be seen in ice cores from the Antarctic and Greenland dating back tens of thousands of years.

Changing relative abundances of isotopes of hydrogen and oxygen trapped in bubbles in the ice correlate with changes in global temperatures. Those ice cores point to a recent and on-going warming trend on earth. Other evidence for this warming trend comes from shrinking glaciers and ice caps, shifting distributions of species worldwide, and of course the recent “global warming” temperature trajectory.

Paralleling that warming has been a dramatic increase in human-generated CO2 in the earth’s atmosphere.

Most scientists believe climate change is happening and that humangenerated CO2 is at least part of the reason.

Still, this remains an extremely divisive issue. I recently overheard the chairman of a board for the University of California commenting on the breadth of the evidence for climate change, dismissing it by saying “it still doesn’t provide proof.” He is correct, but his conviction underlines a misunderstanding about science. Charles Darwin never “proved” that living things evolved by natural selection. What he did do was amass evidence from multiple sources, from taxonomy, from animal breeders, and from biogeography, that together made an exceedingly compelling case for his idea. No other theory has been put forth that explains all the evidence so completely. And so it is for modern climate change.

Warming won’t be the only change. Some areas will get much more rain, and some, like our deserts, are likely going to get drier. Weather will likely become more extreme at all ends of the temperature-rainfall spectrum. From just a human-economics perspective the possible impacts are far from trivial and could include:

  • Less snow, and so less natural water storage in the mountains
  • Higher water needs to offset increased evaporation rates for agriculture and urban uses, but in some areas like the southwest U.S. less water will be available
  • Wildfire season starting earlier in the year and fires growing larger, spreading faster due to dry, insect, and drought weakened trees and shrubs; higher fire-fighting costs; and less lumber available for building
  • Higher food production costs (either pay more for more water or ship food from Canada)
  • Higher energy costs (less water in reservoirs to produce hydroelectric power, more energy needs to run more air conditioners)
  • Higher insurance rates (to cover losses from flooding and drought and possibly hurricanes)

Some of these impacts seem to be cut from the headlines of today’s newspapers. Climate change is not (just) an issue to be faced by our grandchildren, the effects may have already begun.

Species such as this Coachella Valley fringe-toed lizard that are restricted to specific sand dunes won’t be able to easily shift upslope or northward to track shifting climates, and so are particularly at risk as climates warm and get drier. Cameron Barrows photo
Species such as this Coachella Valley fringe-toed lizard that are restricted to specific sand dunes won’t be able to easily shift upslope or northward to track shifting climates, and so are particularly at risk as climates warm and get drier. Cameron Barrows photo

Past climate changes have been implicated in mass extinctions. My own research in this area has focused on how desert plants and animals will fare in the face of predicted modern warming. We recently completed a project with Joshua Tree National Park addressing the climate change fate of its iconic namesake, the Joshua trees. Previous research, looking at the entire distribution of Joshua trees, concluded that this species could not survive predicted climate shifts and would soon no longer exist in much of California; certainly they would not exist at their southernmost distribution within Joshua Tree National Park. Rather than rushing to change the name to “Creosote Bush National Park,” the National Park Service and UC Riverside’s Center for Conservation Biology teamed up to see if we came to the same conclusion focusing just on Joshua trees within the park.

On one hand Joshua trees in the Park occur at the southernmost edge of the species range and so would likely be subjected to a greater shift in temperature and rainfall than populations further north.

On the other hand, being at the edge of their range, the Park’s Joshua trees have always had to deal with more extreme climates and so might have adaptations allowing them to survive. Our first step was to create a model that described environmental characteristics corresponding to the current distribution of Joshua trees. We then tweaked the model by 1°, 2°, and 3°C (maximum July temperature) to see if there was anywhere within the park that would continue to provide conditions similar to where they thrive today.

The bad news was that Joshua trees are very sensitive to climate change and their potential range decreased with every incremental temperature tweak of the model.

The good news was that under a worst case scenario (+3°C) there was still habitat left for this icon of the Mojave Desert; Joshua Tree National Park should be able to keep its name.

Projecting results that might not be seen for many decades makes it difficult to evaluate the accuracy of the model’s predictions. We came up with the idea of measuring whether climate change levels so far had impacted the most sensitive life stage for Joshua trees – when they are seedlings and lack the water and nutrient storage to withstand drought. To answer that question we first needed to know where the seedlings were. We drafted an “army” of citizen scientists, students and desert enthusiasts of all ages and backgrounds.

Volunteer “citizen scientists” collecting data on seedling Joshua trees, documenting that the impacts of climate change are already occurring. Cameron Barrows photo
Volunteer “citizen scientists” collecting data on seedling Joshua trees, documenting
that the impacts of climate change are already occurring. Cameron Barrows photo

We gave them a GPS unit and a meter stick and then deployed our army with the directions to find the smallest Joshua trees they could, measure them, and then provide us the coordinates.

The smallest one found was just 5 centimeters; overall we received over 1000 new seedlings records. Then, using those seedlings 30 cm or less in height (about one foot) we created a new model of their distribution.

The seedling model was a near match to the adult Joshua tree model we created that had been tweaked with a +1°C change in mean July maximum temperature.

We went to the weather archives for the city of Twenty-nine Palms and found that compared to mean temperatures prior to the 1970s there was currently a mean change of +1°C in July maximum temperature. It was an amazing match between modeled projections and real changes in where Joshua trees were successfully reproducing.

Our current project is to build a network of monitoring stations where we can measure real changes in the distributions of plants and animals to track the impacts of climate change on one of our most precious resources, Joshua Tree National Park. We will need citizen scientists once again, so let us know if you are ready to be drafted.

Climate change will have a substantial impact on people and biodiversity. To slow and eventually reverse that trajectory will mean reducing our reliance on fossil fuels. It is a simple answer, but with no easy, or seemingly practical way to implement it.

Energy conservation and efficiency are part of the equation, and shifting to non-carbon energy sources such as wind and solar is another part of the solution. For the first time, our government is taking this seriously and is promoting renewable energy. However, their approach may need some tweaking. They have identified vast tracts of public land across our deserts to be developed for solar and wind energy. Each project will be built at an industrial scale of up to 5 to 10 square miles; several have already been built.

Each will require new roads, new transmission lines, and general infrastructure to build and operate them. Each being built on otherwise undisturbed, wild desert land.

Some colleagues and I just finished an analysis of the biodiversity of lizards in North America. The one site with the highest species richness included much of Joshua Tree National Park and extended to the northern half of Anza Borrego Desert State Park.

From the perspective of lizards it has higher biodiversity than any other region in North America, including both the U.S. and Mexico.

But from the distance of Washington DC, our desert must look like a wasteland, so much so that almost all the Washington DC-based environmental organizations signed a letter supporting the use of our undisturbed desert lands to begin to solve our national energy needs and to begin the shift away from a dependence on fossil fuels, foreign and domestic. Roof-top solar has many fewer impacts, as would be the case if the industrial-scale solar fields were installed on abandoned agricultural lands. The Desert Renewable Energy Conservation Program (DRECP), at least in concept, would preserve those areas vital to maintain the rich plant and animal life found here along with areas that appear to be important natural carbon sinks. It would also identify those desert sites that could be converted to solar “farms” without compromising the natural heritage of our desert. Doing nothing can’t be an option, but doing it right should be.

Dr. Cameron Barrows is an Associate Research Ecologist with UC Riverside’s Center for Conservation Biology. He has been conducting research in the California desert for nearly 30 years, focusing on understanding the role of anthropogenic change of desert biodiversity.