83-4 Farouk El-Baz Award: Critical Zone Aeolian–Ecological Feedbacks at Multiple Scales in Drylands

Abstract:

The critical zone is commonly conceptualized as a vertically coupled system, but in drylands its behavior also depends on horizontal exchanges among vegetation patches, landforms, and regions. Wind makes these exchanges especially nonlocal: ecological structure controls aeolian transport, while the redistribution of sediment, nutrients, and seeds modifies soils, vegetation, and subsequent transport. Here I synthesize field experiments, spatial analyses, remote sensing, and conceptual models to show how these reciprocal interactions operate from meters to continental scales.

At patch scales, vegetation partitions wind shear stress and interrupts sediment-transport pathways. Consequently, the amount and spatial arrangement of bare ground—not vegetation cover alone—govern the connectivity of erosion and deposition. Precipitation-by-connectivity experiments in the Jornada Basin demonstrate that manipulating transport pathways changes plant establishment and cover, with effects contingent on water availability and ecosystem state. The Pulse–Interactions–Reserves–Feedbacks–Community–Trajectory (PIRFCT) framework places these responses in a longer-term context: pulses alter interactions and redistribute reserves; those changes modify feedbacks, reorganize communities, and shape trajectories. Aeolian transport therefore propagates local responses through space and can reinforce patchiness, thresholds, lags, and hysteresis during grassland–shrubland change.

At landscape and regional scales, this same mechanism amplifies seemingly modest land-surface change. Across an agricultural–steppe gradient in Niger, satellite estimates of exposed soil combined with reanalysis winds show that relatively small differences in soil exposure can produce much larger differences in potential aeolian transport because vegetation sheltering is nonlinear. Land-use and vegetation change can therefore reorganize source areas and regional dust loading before changes in total cover appear dramatic.

At continental scales, land–atmosphere coupling can close the loop. In the Sahel, vegetation loss can increase local dust emissions and reduce atmospheric moisture recycling; dust may also suppress precipitation, creating the potential for a low-rainfall/high-dust state. At the same time, circulation links rainfall to remotely sourced Saharan dust, making feedback strength context dependent. Together, these results suggest that aeolian transport is simultaneously a response to ecological structure, a driver of critical zone reorganization, and a pathway through which land surface change can influence climate. Recognizing these nested feedbacks is essential for predicting dryland landscape evolution and identifying when local management of connectivity can alter broader ecosystem trajectories.

Geological Society of America Abstracts with Programs. Vol. 58, No. 5, 2026

doi: 10.1130/abs/2026AM-19171

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