CARBON SEQUESTRATION IN OUR DESERT LANDS
Essential to California’s 30X30 Initiative
by Susy Boyd
California’s laudable efforts to conserve 30% of our state’s lands and coastal waters by 2030 have not been lost on our desert region. In fact, a small but steadfast collection of environmental groups and scientists have been working over the past year to ensure that the desert takes its proper place at the 30X30 table. As the largest intact ecosystem in the lower 48 states, comprising a quarter of the state’s landscape, it seemed reasonable enough that the desert region would play a significant role in 30X30. But it hasn’t been quite that simple.
The California desert has been hung up in a limbo state of perception. The public is catching on to its supernatural beauty evidenced not only by record-snapping visitation to our National Parks, Monuments, and Preserves but more recently by a real estate boon spurred by city dwellers looking to change up their world. In 2011, visitation to Joshua Tree National Park was about 1.4 million. By 2021, it had surpassed 3 million visitors for the first time. Real estate analyst Redfin reports 69% growth in home values in Joshua Tree between 2020-2022. Demand outstrips supply.
At the same time, misperceptions about ecological processes and carbon sinks in the desert have remained persistent. And these misperceptions have created roadblocks for the desert region in taking on its full role in the state’s far-reaching conservation efforts. A coalition of environmentalists and scientists, the Inland Deserts Working Group1 (IDWG) Science Team, functions as an informal liaison between desert concerns and the state’s 30X30 work. Much of IDWG’s work has been to engage cooperatively with California Natural Resources Agency (CNRA) staff who are leading the 30X30 work to create a more holistic understanding of the desert as an ecosystem.
The Intersection of 30X30 and Our Desert Lands
While the broad goal of 30X30 is to conserve 30% of the state’s lands and waters, there are three pillars of the plan to get there. One of the foundations is carbon sequestration to combat climate change, a second is protecting California’s spectacular biodiversity, and a third is access for all. This report focuses on the first pillar, though there’s much to be said for the other two. The state has put a great deal of emphasis on “Nature Based Solutions” as a result of Governor Gavin Newsom’s Executive Order N-82-20. The EO seeks to advance biodiversity conservation as an administration priority and elevate the role of nature in the fight against climate change. To meet atmospheric carbon reduction goals, nature itself, if conserved, functions as a carbon sink.
The challenge for the desert region isn’t so much its capacity to store carbon, but the widespread misperception that the desert ecosystem lacks that capacity.
California’s Deserts Store Up to 10% of the State’s Carbon Emissions
Visually, it’s an understandable flaw to dismiss the desert as a carbon sink. When we look at a redwood tree and make the case that carbon is stored in its tall broad trunk, in its fine needles and overstory, in its roots, in its deep red soil, there’s little room for dispute. But the desert’s carbon sequestration capacity operates in its own unique way. A way that makes complete sense for its harsh, water-deprived environment. In a desert, carbon sequestration is upside down. Botanist Robin Kobaly aptly describes the ecosystem as an underground forest.2 We can’t see it, but it exists. The desert mesquite tree is a good example. Older mesquites reach an aboveground height of 20-30 feet and appear almost more shrub-like than as a tree. But their roots can extend for several hundred feet, far into soil depth, reaching for life-sustaining water.
Comparison of amounts of carbon stored as inorganic carbon (223.2 kg/m2) [soil carbonate-C] vs. organic carbon (6.8 kg/m2) [soil organic-c] within layers of desert soil at the USDA-ARS Jornada Experimental Range in northern Chihuahuan Desert New Mexico. In the desert, carbon sequestration is primarily an underground process. Credit: Dr. H.C. Monger, New Mexico State University
Roots and their attached fungal root partners exhale CO2 which reacts with calcium to form calcium carbonate crystals, or caliche. Atmospheric carbon is transferred – and stored – underground, in the caliche. If the soil is left undisturbed, the carbon remains underground for thousands of years. Glomalin is another critical means of carbon storage in the desert ecosystem. It’s made from atmospheric carbon that’s been converted to sugars and sent down to the roots, then secreted around the fungal threads connected to these roots. There are miles of carbon-storing glomalin threads in one cubic foot of undisturbed desert soil. And glomalin stores a third of the world’s soil carbon.
Caliche forms the uppermost layer—the "caprock"—of the sediment. Edge of La Mesa Surface, west of the Rio Grande Valley. Credit: Dr. A.H. Harris, UTEP Biodiversity Collections
The desert distinguishes itself from other ecosystems by having high amounts of soil inorganic carbon (SIC). Inorganic carbon “counts” when it comes to carbon sequestration. The desert’s carbon storage capacity is primarily owed to soil inorganic carbon, which has long been neglected as a significant C sink. A 2000 study found that globally, desert soils sequester about 800-1700 Petagrams of carbon. Studies estimate soil inorganic carbon to account for a third of the total C pool in soils worldwide. With soil inorganic carbon constituting such a large component of the global carbon pool, excluding this segment skews global carbon accounting.
In the state’s 30X30 carbon accounting framework, this exclusion appears to be a result of difficulty in modeling SIC. Since one goal of 30X30 is to develop management strategies across state ecosystems to maximize carbon sinks, inability to assess projections and changes in desert carbon stock (also called “flux”) creates a challenge for inclusion of SIC. At the same time, the SIC pool is an integral part of the global carbon pool and excluding this crucial component minimizes the fundamental importance of desert ecosystems in addressing climate change goals at both regional and global scales.
The Desert Time Scale
Just as our iconic desert tortoise is slow but steady, so too is carbon storage in the desert. The ecosystems that 30X30 work focuses on are forests, grasslands, wetlands, croplands… even developed lands. Carbon in these ecosystems is stored primarily in aboveground biomass. As you would imagine, these systems are exposed to weathering, hydrology events, and human impact. Especially in a managed forest where inventory is regularly harvested, grown, and measured, carbon moves around a lot. Even carbon stored in cut lumber is part of the accounting trajectory. Carbon in a forest is prone to a great deal of flux. The same doesn’t hold true for the desert. Because carbon is stored primarily underground, in roots, in caliche, it stays put for the most part, barring human disturbance. Caliche layers can be thousands of years old. It takes a very long time to form the caliche, but just minutes of a bulldozer’s work to release ancient carbon stores back into the atmosphere. The simplicity of carbon sequestration in the desert can be difficult for decision makers working on 30X30 strategies to grasp because the best management strategy for desert carbon sequestration is to leave it alone.
A Macro Look at Desert Carbon Sequestration
One of the ways to think about how deserts function as carbon sinks is in terms of area units. So, acre for acre, a forest stores more carbon than a desert. But what if there are many acres of desert lands relative to acres of forest or grasslands? The vastness of arid lands across the planet accumulatively make them a grand carbon sink. Arid regions, which cover about 47 percent of the earth’s land mass, are thought to make up the world’s third-largest carbon sink on land. This phenomenon is expressed when we look at the rankings of carbon storage in our National Parks.3
It may be surprising to find Death Valley and Joshua Tree National Parks, and Mojave National Preserve, ranked higher for Carbon Sequestration Value than Redwood National Park and the Santa Monica Mountains NRA. Per unit of area, this would not be the case. But the sheer vastness in size of our desert parks makes up for carbon accounting. And this same scale plays out across our planet.
Top 20 NPS Units by Carbon Sequestration Value.
Credit: NPS/Dept of Interior
Carbon sequestration in deserts is an understudied, poorly funded, and perhaps most importantly undervalued process. But there’s enough scientific evidence to date showing that deserts and arid lands may well be a critical, overlooked component of the global carbon pool. And if we are to enact policies such as state and federal 30X30 efforts with the intent of addressing our climate change challenge, it becomes of the utmost importance to start taking our desert lands seriously as a critical carbon sink.
1) Inland Deserts Working Group (IDWG) Science Team, chaired by Robin Kobaly (The SummerTree Institute); Moises Cisneros (Sierra Club); Sendy Barrows (COFEM); Pat Flanagan, Arch McCulloch, and Dr. Gary Stiler (Morongo Basin Conservation Association); Dr. Michael Allen (UC Riverside); Joan Taylor (Sierra Club); Dr. Cameron Barrows (UC Riverside) and Susy Boyd (MDLT).
2) Desert Report, March 2019.
3) Richardson, L., C. Huber, Z. Zhu, and L. Koontz. 2014. Terrestrial carbon sequestration in national parks: Values for the conterminous United States. Natural Resource Report NPS/NRSS/EQD/NRR—2014/880. National Park Service, Fort Collins, Colorado.
Susy Boyd works as Public Policy Coordinator for Mojave Desert Land Trust. She holds a Master of Natural Resources degree from Oregon State University where she researched climate change impacts on Mexico’s Yucatan forests. She is an avid explorer and outdoors lover.