Significance: Despite their small height and stunted appearance, mangroves along the desert coasts of Baja California have compensated for sea-level rise during the last two millennia by accreting on their own root remains. In doing so, they have accumulated very large amounts of carbon in their sediments (900–3,000 Mg C/ha), often higher than that accumulated under tall, lush, tropical mangrove forests. Mangroves represent the largest carbon sink per unit area in Mexico’s northern drylands. Our results highlight the global importance of mangrove conservation in this region.

The seasonal timing of seed germination determines a plant’s realized environmental niche, and is important for adaptation to climate. The timing of seasonal germination depends on patterns of seed dormancy release or induction by cold and interacts with flowering-time variation to construct different seasonal life histories. To characterize the genetic basis and climatic associations of natural variation in seed chilling responses and associated life-history syndromes, we selected 559 fully sequenced accessions of the model annual species Arabidopsis thaliana from across a wide climate range and scored each for seed germination across a range of 13 cold stratification treatments, as well as the timing of flowering and senescence. Germination strategies varied continuously along 2 major axes: 1) Overall germination fraction and 2) induction vs. release of dormancy by cold. Natural variation in seed responses to chilling was correlated with flowering time and senescence to create a range of seasonal life-history syndromes. Genome-wide association identified several loci associated with natural variation in seed chilling responses, including a known functional polymorphism in the self-binding domain of the candidate gene DOG1. A phylogeny of DOG1 haplotypes revealed ancient divergence of these functional variants associated with periods of Pleistocene climate change, and Gradient Forest analysis showed that allele turnover of candidate SNPs was significantly associated with climate gradients. These results provide evidence that A. thaliana ’s germination niche and correlated life-history syndromes are shaped by past climate cycles, as well as local adaptation to contemporary climate.

We tested how sediment trapping by hydroelectric dams affects tropical estuaries by comparing two dammed and two undammed rivers on Mexico’s Pacific coast. We found that dams demonstrably affected the stability and productivity of the estuaries. The two rivers dammed for hydroelectricity had a rapid coastal recession (between 7.9 and 21.5 ha year⁻¹) in what should otherwise be an accretional coastline. The economic consequences of this dam-induced coastal erosion include loss of habitat for fisheries, loss of coastal protection, release of carbon sequestered in coastal sediments, loss of biodiversity, and the decline of estuarine livelihoods. We estimate that the cost of the environmental damages a dam can cause in the lower part of basin almost doubles the purported benefits of emission reductions from hydroelectric generation.

Societal Impact Statement: Climate change is dramatically restructuring agriculture and damaging crops, food security, and human health, especially in deserts. To radically redesign food systems to buffer against climatic disruptions, we focus on agroecological function, human health, and community well‐being. Using arid North America (“Aridamerica”) as a laboratory for the future, we employed 18 criteria to select 17 desert plant genera with high potential as food crops. When integrated into perennial polycultures modeled after arid ecosystems and traditional knowledge, desert plants can stabilize yields, produce disease‐preventing foods, and generate rural livelihoods. We envision food systems that can reduce disparities while enhancing resilience in a hotter, drier world.Summary: Climate disruptions and water scarcity are threatening food security and human well‐being. We provide a framework for selecting a more diverse set of arid‐adapted food crops to reduce food system vulnerabilities to climate change, climate‐related illness, and economic disparities in arid lands. We constructed a list of candidate crops based on the diets of the Comcaac, O'odham, and Pima Bajo peoples of the Sonoran Desert. Representative genera were then screened for traits related to agroecological functionality, human health, community well‐being, and agronomic suitability. Of the 154 species (86 genera) used by these Sonoran Desert Indigenous cultures, 101 species (80 genera) were more broadly used in Aridamerica, suggesting wide acceptability and value of desert plants for arid‐adapted agriculture in North America. We highlight 17 genera with high potential to simultaneously improve agricultural resilience, human health, and community prosperity in the face of climate change, over a third of which are water‐use efficient crassulacean acid metabolism (CAM) succulents. Assembling these candidate crops into perennial polycultures coupled with solar energy and rainwater harvesting systems can maximize yield reliability while minimizing fossil fuel, agrichemical, and surface and groundwater use. Now is the time to invest in desert‐adapted farming and food systems, with climate change already accelerating damages to agricultural landscapes. Biomimicry and traditional knowledge can aid in designing co‐located food, water, and energy provisioning systems adapted to arid climates and scarce resources that improve agroecological and human health. Adopting such designs will require transdisciplinary integration of plant, environmental, social, and health sciences.