Evaluating Landscape Degradation Along Climatic Gradients During the 1930s Dust Bowl Drought From Panchromatic Historical Aerial Photographs, United States Great Plains

The United States Great Plains (USGP) are some of the most productive rangelands globally and a significant carbon sink for the atmosphere, but grassland response to precipitation is highly variable and poorly constrained over time and space. There is a rich historical aerial photographic record of the USGP which provides an unparalleled view of past landscapes and allows for evaluation of surficial response to drought beyond the satellite record, such as during the 1930s Dust Bowl Drought (DBD). This study classified the extent and loci of surficial denudation from seamless mosaics of radiometrically corrected and georectified digitized aerial negatives acquired in the late 1930s from six counties distributed across USGP ecoregions. The dominant sources of degradation found for sites east of the 100th meridian are cultivated fields and fluvial deposits, associated with woody vegetation response to water availability in uncultivated areas. For sites to the west, denuded surfaces are predominantly eolian sandsheets and dunes, correlated with intensity of drought conditions and reduced plant diversity. Discrete spatial signatures of the drought are observed not only within the classically recognized southern Dust Bowl area, but also in the northern and central plains. Statistical analyses of site variability suggest landscape response to the DBD is most strongly influenced by the arid–humid divide and severity of precipitation and temperature anomalies. With a projected increase 21st century aridity, eolian processes cascading across western grasslands, like during the Dust Bowl, may significantly impact future dust particle emission and land and carbon storage management

Reconstructing land surface processes of the 1930s Dust Bowl drought, U.S. Great Plains.

Mineral dust aerosols are a key component of the Earth system and a growing public health concern under climate change as levels of dustiness increase. The U.S. Great Plains is particularly vulnerable to dust episodes, but land-atmosphere feedbacks contributing large-scale dust particle transport are poorly constrained, introducing uncertainty in future dust-borne risks to air quality and drought persistence. The 1930s Dust Bowl drought (DBD) is a well-studied, historical example of extreme climate variability. A leading hypothesis to explain the intensity of the DBD is landscape denudation associated with agriculture. However, historical reanalysis indicates that ~30% of the Great Plains was cultivated in the 1930s, thus human agency as the ultimate cause of degradation has been questioned. This work explores the surface processes and meteorological conditions influencing dust particle emission and eolian transport from historical aerial photographs and archival records of the Soil Conservation Service, combined with contemporary field surveys using a Portable In-Situ Wind Erosion Laboratory (PI-SWERL). Over 40% of the variance in DBD dust storms is explained by air temperature at the surface and 850 hPa and relative humidity at 850 hPa, highlighting the impact of elevated temperatures and spring precipitation deficits associated with 1930s heatwaves. The dominant sources of degradation found for sites east of the 100th meridian are cultivated fields and fluvial deposits. For sites to the west, denuded surfaces are predominantly eolian sandsheets and dunes, correlated with intensity of drought conditions and reduced plant diversity. Discrete spatial signatures of the drought are observed not only within the classically recognized southern Dust Bowl area, but also in the northern and central plains. The PM₂.₅ and PM₁₀ emissivity estimates for a single dust event with winds over 6 m s⁻¹ in the study area were 510-4,514 μg m⁻³ d⁻¹ and 4,700-41,607 μg m⁻³ d⁻¹ respectively, similar in magnitude to current dust storm events from North Africa and East Asia. Drought frequency is forecast to increase in late 21st century, potentially with greater severity than the DBD, and may be associated with magnitude increase in atmospheric dust loads

A geospatial approach to prioritizing drift cells for strategic protection, restoration, and enhancement

The Washington Department of Ecology Coastal Monitoring & Analysis Program has developed an objective, systematic, and data-based approach to identifying and prioritizing intact shorelines (drift cells) that offer a high potential for learning, protection, and restoration, combined with a convergence of stakeholder interest and institutional capacity for collaborative nearshore ecosystem management. The approach and current criteria used identifies highest-priority drift cells with feeder bluffs that actively provide sediment to the nearshore and sustain an unusually high level of ecosystem services. The approach is intended to serve as a model for determining where in the landscape to strategically invest capital and social inputs for protection and restoration efforts. Spatial analysis of widely available physical, ecological, and social data and the use of multiple criteria, metrics, and their relative weighting provide initial assessment of high-value locations, while site monitoring, characterization, and geomorphic change analysis can provide refined information to guide the specific approach to ecosystem management for each site. With over 1000 drift cells in Puget Sound, the current project identified 17 ‘top-tier’ and 24 ‘second-tier’ drift cells as well as 105 ‘third-tier’ drift cells that represent 163, 143, and 406 km of shoreline, respectively. The drift cells within the ‘top-tier’ category are predominantly located in north Puget Sound; only one site is located in south central or south Puget Sound sub-basins, whereas 8 of the 24 ‘second-tier’ sites are located in these southern basins. The current criteria used emphasizes drift cells that offer the greatest potential return on ecosystem services per quantity of capital and social investment, thus there is an inherent bias toward projects involving protection over restoration. However, given the anthropogenic overlay and influence on the landscape, opportunities for restoration are essentially ubiquitous