On April 10, 2023, exceptional weather conditions over southern Israel produced an extreme rainstorm. The peak precipitation, with a maximum rainfall depth of 62 mm and rain intensities exceeding 50 mm h⁻¹, fell over the hyper-arid southern Negev and Arava Valley and generated a mega flash flood in Wadi Zihor. This ephemeral stream channel supported a comparatively dense cover of vegetation, predominated by Acacia raddiana, Acacia pachyceras, Tamarix nilotica, and Tamarix aphylla. To determine the properties of the flash flood, we used post-flood ground-based measurements and calculations of shear stress and peak discharge along the wadi. Also, we used pre- and post-flood satellite images to assess the flood’s impact on woody vegetation cover along the ∼17 km-long wadi bed. Calculations based on data collected by the Israel Water Authority implied a peak discharge of 585 m³/s at the wadi outlet, indicating a low-frequency flash flood of less than once in 150 years. The pre-flood’s 12.7 % vegetation cover throughout the wadi bed decreased to 7.5 % after the flood, corresponding to a 41 % net loss. To detect differences in tree removal extent along the wadi, we divided its entire length into 24 equal segments, and separately assessed the vegetation cover before and after the flood. Vegetation cover loss was 10.8 % in the wadi’s uppermost segment, whereas its lowermost segment lost 51.6 %. Overall, a significant and strongly positive (r = 0.88) correlation was recorded between the accumulated watershed area (downstream) and the extent of tree cover loss. Among other factors, this effect seems to be predominantly determined by the increasing shear stress and peak discharge downstream. Forecasted climatic change scenarios, with increasing magnitude and frequency of extreme rainstorms and floods across the world’s drylands, highlight the need for more data collecting and analyzing of those events impact as described in this study.

Despite the significant global impact of oil spills on the environment, little is known about the effects of oil spills on animals in terrestrial ecosystems, particularly in desert environments. In contaminated areas, habitat selection can be a crucial behavior determining individuals survival as well as a potential indicator of an ecosystem’s condition. This is especially relevant for ground-dwelling insects, whose close interactions with the soil make them valuable bioindicators of soil quality.

This study aimed to determine the long and short-term effects of oil spills on the microhabitat selection behavior of ground-dwelling insects in a hyper-arid desert. Soil samples were collected from a nature reserve that experienced two oil spills, one in 1975 and another in 2014. We conducted microhabitat selection experiments in laboratory conditions using the ground-dwelling Mesostena angustata beetles and Myrmeleon hyalinus antlion larvae.

When given a choice between clean soil (control) and soil contaminated in 2014, both beetles and antlions selected the clean soil, with antlions exhibiting reduced movements and no pit-trap digging in contaminated soil. Surprisingly, both beetles and antlions selected the soil contaminated in 1975 over other soil types. However, the antlions kept relocating their pit-falls traps in the 1975 polluted soil, which may indicate they perceived this soil as less suitable for pit digging. When given a choice between three types of soil, the beetles clearly preferred dark, oil-contaminated soils and avoided the clean soil.

Our study highlights the complex and varied effects of oil spills on microhabitat selection behavior in ground-dwelling insects, indicating the importance of considering long-term effects in future restoration efforts.

Implications for insect conservation: This study shows that oil contamination impacts ground dwelling insects behavior even more than four decades after an oil spill. The attraction of both insect species to the contaminated soil from 1975 may be an indication of an ecological trap for these species in the field. We conclude in this study that the habitat selection behavior of the antlion larvae may be a good behavioral indicator for habitat restoration purposes.

Deserts are characterized by unpredictable precipitation and extreme temperatures. Their fauna and flora are sensitive to anthropogenic environmental changes, and often recover slowly from environmental disasters. The effects of oil spills on the biota of desert regions, however, have scarcely been studied. We predicted that terrestrial invertebrates suffer long-term negative effects from an oil spill, due to their close association with the substrate. Thus, we investigated the effects of two oil spills that occurred in 1975 and 2014 in the hyper-arid ‘Arava desert (Israel), on a spider that constructs silk-lined nests in burrows in compact, sandy soil in this extreme desert habitat. The spider, Sahastata aravaensis sp. nov. (Filistatidae), is described herein. We assessed spider burrow abundance in plots located in oil-contaminated and nearby uncontaminated clean soil (control) areas over five consecutive years and measured habitat characteristics in these plots. In the laboratory, we determined the preference of individuals for clean vs. oil-contaminated soil as a resting substrate. Finally, as this species was previously undescribed, we added a new species description. The abundance of Sahastata was significantly lower in oil-contaminated plots, and this was the case in the 40-year-old oil spill (1975) as well as in the recent one (2014). In laboratory tests, spiders showed a significant preference for the clean soil substrate over the oil-contaminated substrate. In the field, soil crust hardness and vegetation density did not differ significantly between oil-contaminated and control plots, but these measures were highly variable. The burrows were significantly clustered, suggesting that the young disperse only short distances. In the laboratory adult spiders did not dig burrows, perhaps indicating that adults remain permanently in their natal burrows and that in the field they may use vacant burrows. We conclude that Sahastata populations were affected negatively by the oil spills and these effects were long-lasting. We propose that by monitoring their spatial distribution, burrow-dwelling spiders such as Sahastata can be used as effective bioindicators of soil pollution in desert habitats.

Antlions (Neuroptera) are a group of sit-and-wait predator insects, with some species further specializing in digging conical pit-traps in the ground in order to catch prey. Studies on antlions’ predators are scarce with only few generalist predators known to feed on them. Here we report for the first time on field observations of antlions’ predation by three scorpion genera. We suggest that scorpions may be common predators of antlions, at least in the hyper-desert environment of southern Israel. The effects of predation risk on the behavior of sit-and-wait and particularly on trap-building predators received little attention in the literature. In light of our observations, we posit that predation risk must be taken into serious consideration in future research of antlions in particular, and sit-and-wait predators in general.

Deserts are the most frequent locations of terrestrial crude oil contaminations. Nevertheless, the long-term effects of petroleum hydrocarbons on desert ecosystems are still unknown, which makes risk assessment and decision making concerning remediation difficult. This study examined the long-term effects of petroleum hydrocarbons on perennial desert vegetation. The study site was a hyper-arid area in the south of Israel, which was contaminated by a crude oil spill in 1975. The contaminated area was compared to uncontaminated reference areas. The composition of perennial plants 40 yr after the oil spill was not significantly affected by the contamination. However, the size distribution of the two most dominant shrub species, Salsola cyclophylla Baker and Hammada salicornia (Moq.) Iljin., and the only tree species, Acacia raddiana Savi and Acacia tortilis (Forssk.) Hayne, were different from the reference. These differences can be explained by decreased recruitment. The estimated recruitment of Acacia in the last 40 yr post oil spill was 74% less than recruitment in the reference area. Low recruitment of Acacia may in the future lead to the loss of tree cover, which would change the entire ecosystem, as Acacias are keystone species on which a number of microorganisms, plants, and animals rely. Remediation of oil spills and preventative measures are recommended.