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A New Strategy Is Urgently Needed to Deal with Climate Impacts on Desert Agriculture in the US. Southwest

By: Gary Paul Nabhan

  • We Need to Advance “Trans-Situ Conservation” of Arid Adapted Crops and Their Wild Relatives in a Single, Integrated Site in Arizona’s Desert Borderlands
  • We Propose Linking an Existing USDA/ARS Long-Term Agricultural Site (LTAR) at Walnut Gulch Experimental Watershed with a New USDA/ARS National Arid Land Plant Genetic Resource Unit in Southern Arizona


A recent analysis (1) summarizing the Environmental Protection Agency’s Climate Change Impacts and Risk Analysis (2) concluded that by  2090, climate-induced impacts on agriculture and 21 other natural resource-based sectors of our U.S. economy could cost over $224 billion more per year. Considerable research confirms that because of water scarcity, and increased heat or solar radiation during flowering and fruiting—in addition to water scarcity-crop yields will decline for most staple crops, as well as many fruits and vegetables (3).

As a result, most of the climate change impacts on the agricultural sector would be passed on to food consumers, in effect, to all taxpayers. In Arizona alone, the 1 Tier One water shortage in the Colorado River has triggered a 512,000-acre-foot reduction in Arizona’s deliveries of irrigation water that is projected to immediately cost farmers over $100 million in farm sales this next year, while eliminating nearly 500 jobs (4, 11). 

The devastating effects of climate change on agriculture in the borderland region have prompted us to bring federal agencies, non-profits, universities, plant breeders and farmers together to forge new long-term solutions to arid adapted crop selection and the conservation of crop wild relative in border states.

We propose to rapidly expand the USDA’s efforts to collect, conserve, evaluate and regenerate arid-adapted plant genetic resources by co-locating an Arid Lands Plant Genetic Resource Institute unit with a Long-Term Agricultural Site in southern Arizona where a sizeable diversity of arid adapted crop wild relatives still occur in wild habitats. By more tightly linking in situ and ex situ conservation and research measures in a trans situ framework, this effort will integrate the ecology, conservation, and plant breeding of desert-adapted plants into a more cohesive and cost- effective supply chain. Although this proposal is focused on co-locating in situ reserves and ex situ seed banks in border counties of southern Arizona, it will have direct value to both plant breeders and farmers working in the ten western states of the continental U.S.

In a recent article, Silva and Tchamitchian (5) argue that Long-Term Agriculture Sites need to be effectively integrated with other research across scales and disciplines, if we are to address the need for interdisciplinary and transdisciplinary approaches to solve the “wicked problems” facing today’s society (1). One of those wicked problems is the impact that climate change is having upon conventional agriculture in the American West, where it is expected to have overall detrimental effects on most crops and livestock costing billions of dollars of production losses per year (6). Climate change is already exacerbating both abiotic stresses (heat stress, drought stress, salinity stress and damaging solar radiation stress)—and biotic stresses (disease, insects, and competition) on agricultural plants of most kinds (3).

The need for more arid-adapted crop plants with higher heat thresholds during flowering times and greater drought tolerance has grown dramatically over the last decade and will continue to do so (7). While many scientists believe that the wise use of crop wild relatives will be key to adapting agriculture to climate change, most of these from arid land habitats are underrepresented in current gene banks, understudied in their wild habitats, and threatened by many anthropogenic pressures, including climate change itself (8).

One solution to this problem is to integrate in situ and ex situ field research and conservation/regeneration strategies through what we call trans situ conservation (9). Two important features emerge from a trans situ approach of co-locating in situ conservation in wild habitats with nearby ex situ gene bank preservation.  First, integrating in situ and ex situ studies of CWR genetic diversity, adaptation, and ecological interactions advances  crop improvement and in situ management. Second, the complementarity, redundancy, and synergy gained through trans situ conservation buffer climatic, economic, political, and institutional instabilities.

As Anderson and Song have proposed (10), we could advance such an integrated approach to plant genetic resource conservation, evaluation and utilization leveraging interdisciplinary tools (e.g., cutting-edge genomics toolkits, novel ecological strategies, newly developed genome editing technology), so that we can “more accurately predict the probability that species can persist through this rapid and intense period of environmental change, as well as cultivate crops to withstand climate change, and conserve biodiversity in natural systems.”


  1. To rapidly expand the USDA’s efforts to collect, conserve, evaluate and regenerate arid-adapted plant genetic resources in a diversity hotspot of arid-adapted crop wild relatives.
  2. To increase the research interaction among staff at Plant Genetic Resource Units with the staff at Long-Term Agricultural Resource (LTAR) sites to cross-train them for integrated research and conservation of desert wild relatives of crops grown in Western states.
  3. To compare crop plant descriptor data-taking and phenotyping for the same accessions grown in semi-arid temperate zones of the Mediterranean biome of northern California and in the arid subtropical zones of the Sonoran and Chihuahuan desert biomes in Southeastern Arizona.
  4. To hold field days in late summer and spring for both plant breeders and desert farmers to obtain feedback on how to better move arid plant genetic resources through the supply and delivery stream to directly benefit farmers and consumers.
  5. To map and demographically assess wild populations of crop wild relatives in the 150 square kilometer area of the Walnut Gulch watershed (bridging the Sonoran-Chihuahuan ecotone) to track the impacts of climate change through time.
  6. To engage other nearby public agricultural institutions (University of Arizona, New Mexico State University, Jornada Experimental Range, USDA NRCS Plant Material Center in Tucson, AZ and Los Lunas NM) and non-profits (La Semilla Food Center, Borderlands Restoration Network, Native Seeds/SEARCH, Mission Gardens, San Diego Botanical Gardens, etc.) in the regeneration, evaluation, and promotion of desert crops to farmers and gardeners.

Advantages of Such a Co-located Trans-Situ Conservation Initiative:

  1. You can minimize ill effects of disruptive “counter” selection in arid-adapted accessions by regenerating them in true desert climates.
  2. You can more directly engage desert botanists, ecologists and farmers in collecting, describing and evaluating arid land plant genetic resources if you have a training center and 150 square kilometers of desert habitat within a few hours reach of major land grant universities dedicated to arid land natural resources, including the University of Arizona and its Maricopa Agricultural Center, New Mexico State University and University of Texas/El Paso.
  3. You can evaluate how much “descriptors” for gene bank collections of crop wild relatives have become skewed when evaluated outside the natural range of the species and home range of production, since most commonly-used descriptors are phenotypic expressions. 
  4. You will jumpstart the first major American effort—comparable to the International Center for the Potato collaboration with the ANDES, A.C. Parque de la Papa in situ reserve— to geographically couple in situ and ex situ conservation efforts. This would allow for continuous “reciprocal” learning about the dynamics of in situ wild populations that immediately feeds back into a) ex situ regeneration, b) breeder use and c) agro-ecological design of new climate-friendly farmscapes, and vice-versa.
  5. You can optimize trans-situ conservation of arid adapted crop wild relatives and become the first long-term monitoring station in the U.S. for climatic effects on multiple crop wild relatives in the same habitat complex. As many as 50 species of crop wild relatives occur within 60 miles of Tucson and 5 miles of the Walnut Gulch HQ in Tombstone.
  6. You can lead in developing solutions for a climate-friendly food system in a hub of innovation  southeastern Arizona through key partnerships with Biosphere 2, the first UNESCO City of Gastronomy designation in the U.S. with Tucson as its hub, and the new Santa Cruz Valley National Heritage Area.,.
  7. You can increase funding opportunities by presenting a bold, new, integrative approach that will move the needle towards climate resilience. 

Justifications for Establishing a USDA/ARS Arid Land Plant Genetic Resource Unit between Tucson and Tombstone Arizona:

  1. The Need for Arid-Adapted Crops in Arizona is Urgent. As Chelsea McGuire and David Muench of the Farm Bureau reported in August 2021 in Market Intel (11): “As of June 11, 2021, fourteen of Arizona’s fifteen counties were in D4 (exceptional) drought designation. The same drought that rages across the entire American West is threatening the livelihoods of Arizona’s farmers and ranchers, no matter the commodity they grow. The impacts have been devastating to the state’s $23.3 billion agricultural industry, in ways that may change the face of farming and ranching in Arizona for generations to come. [Because of Colorado River water rationing that will reduce irrigation water delivery from allotments by a third as of 2022…] the University of Arizona estimates that the economic impact of losing that water will include a loss of more than $100 million in sales, $66 million in gross farm-gate sales and up to 480 full or part-time jobs. From “Assessing Western Drought Conditions – A Snapshot of How Arizona’s Farmers and Ranchers are Coping with Drought:”
  2. Southern Arizona’s Sonoran and Chihuahuan Desert regions are “laboratories for the future” for arid-adapted agriculture. “We see today’s deserts not as wastelands but as laboratories for the future of agriculture,” affirmed at team of researchers from 5 universities and agricultural research institutes whose work appeared in the journal Plants, People, Planet. “By combining ancient and cutting-edge strategies for dealing with rising temperatures, water scarcity and diseases exacerbated by heat stress, the team hopes to make food production less daunting, dangerous and deadly for future desert dwellers.”  From and
  3. There are 6 world-class arid land plant genetic resources collections already in the Tucson to Tombstone region with which to collaborate:

A Final Word:

 In response to the devastation of the “Dust Bowl” era in the early 1930’s, the Bureau of Plant Industry built a Plant Materials Center with nurseries of arid-adapted plants in Tucson that employed over 400 scientists and technicians at its peak. The USDA Plant Materials Centers in Tucson AZ and Los Luna NM now employ less than 20 scientists and technicians to prepare our farmers for hotter, drier conditions. We will fail unless we ramp up


1.  Dana Nuchatelli. (2019). Climate change could cost U.S. economy billions. Yale Climate Connections.

2.  Jeremy Martinech, et al. (2018). Multi-Model Framework for Quantitative Sectoral Impacts Analysis A Technical Report for the Fourth National Climate Assessment. U.S. Environmental Protection Agency, Washington, D.C.

3.  Gary Paul Nabhan. (2013). Our Coming Food Crisis. New York Times.

4.  Arizona Farm Bureau. (2021). Now that the Tier One Shortages on the Colorado River is here.

5.  E. M. Silva and M. Tchamitchian (2018). Long-term systems experiments and long-term agricultural research sites: Tools for overcoming the border problem in agroecological research and design. Agroecology and Sustainable Food Systems, 42:6, 620-628.

6.  Anon. (2013). USDA Climate Change and Agriculture Report. CC%20and%20Agriculture%20Report%20(02-04-2013)b.pdf

7.  Union of Concerned Scientists. (2019). Climate Change and Agriculture: A Perfect Storm in Farm Country.

8.  J. T. Anderson, and B. H. Song (2020). Plant adaptation to climate change—Where are we? Journal of Systematics and Evolution, 58: 533-545.

9.  H. Dempewolf, R. J. Eastwood, L. Guarino, C. K. Khoury, J. V. Müller and J. Toll (2014). Adapting agriculture to climate change: A global initiative to collect, conserve, and use crop wild relatives. Agroecology and Sustainable Food Systems, 38:4, 369-377,

10.  E. C. Riordan and G. P. Nabhan (2019). Trans situ conservation of crop wild relatives. Crop Science, 59: 2387-2403.

11.  Chelsea McGuire. (2021). Assessing western drought conditions- a snapshot of how Arizona’s farmers and ranchers are coping with drought. American Farm Bureau Market Intel.

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