Caspian lowland desert
The Caspian lowland desert is a salt-rich desert ecosystem located along the northern and northeastern margins of the Caspian Sea, primarily spanning parts of Iran, Turkmenistan, Kazakhstan, and Russia. This unique biome emerged from tectonic activity that closed off a section of an ancient ocean, resulting in a saline depression that fosters a specialized environment for salt-tolerant and drought-resistant vegetation. Predominant plant species include halophytes such as saltworts and oraches, as well as drought-tolerant shrubs and grasses. The desert supports a diverse range of fauna, including various mammals, reptiles, and significant populations of migratory birds.
Characterized by its temperate and arid climate, the region typically receives less than 15 inches of precipitation annually, leading to challenging conditions for both flora and fauna. Human activities, such as livestock grazing, salt mining, and petroleum extraction, are prevalent and economically significant; however, they also pose considerable stress on the fragile ecosystem. The Caspian lowland desert faces threats from climate change, which may exacerbate existing challenges and potentially reduce biodiversity. Overall, the region exemplifies a delicate balance between economic resource utilization and environmental sustainability, warranting careful management to preserve its unique ecological character.
Subject Terms
Caspian lowland desert
- Category: Desert Biomes.
- Geographic Location: Asia.
- Summary: A salt-rich lowland desert ecosystem located along the northern and northeastern margins of the Caspian Sea, this biome sustains salt-tolerant scrub vegetation and both indigenous and migratory fauna.
The Caspian lowlands resulted from the collision of tectonic plates that pinched shut a portion of an ancient ocean in the relatively recent geologic past. The salt-rich depression that formed was key to inducing the conditions that eventually created this unique lowland desert ecosystem. The salt deposits define, in part, the character of the ecosystem and offer various economic benefits.
Situated in an endorheic basin—one with no outflows to the ocean—the Caspian Sea is actually a vast lake in central Asia, but is situated in a climate zone that lends to the brackish nature of its waters. This, in turn, has created a high-saline desert that extends around much of the eastern and northern shores of the sea, through parts of the bordering countries of Iran, Turkmenistan, Kazakhstan, and Russia.
Climate
The lowland desert continues to receive various salts from the weathering of local mountain ranges and the adjacent Caspian Sea during its regressive stages. In the latter case, the salt contributions occur along the margins of the desert because it is in contact with the brackish water of the Caspian Sea as it recedes and evaporates. Contrarily, episodic expansions of the Caspian Sea correspond to freshening events and limited exports of water into the adjacent western portions of the lowland desert. This spurs higher but temporal levels of biological activity.
Although the modern climate of the Caspian lowland desert is temperate and dry, geologic data indicates that the climate of this region was once cool, moist, and supportive of a more diverse ecosystem. In its modern climate, the nearby mountains strip moisture from the air and hinder significant precipitation to the region. This orographic effect exacerbates the effects caused by the lack of precipitation in this region, which is typically less than 15 inches (38 centimeters) annually. Notably, during periods of extended drought, the hard lowland desert soils prevent water infiltration into the ground following precipitation events. This process promotes runoff and the creation of surface pools in low-lying areas.
Vegetation and Animals
Ponded water eventually evaporates and concentrates salt deposits, affecting the soil and water quality of the region, and ultimately the diversity and sustainability of plant and animal groups in the lowland desert. As a result, salt-tolerant (halophytic) and drought-tolerant (xeric) vegetation including shrubs such as tetyr and sagebrush, sedge (Carex spp.), and grass genera such as Stipa and Panicum dominate this ecosystem. Among the predominant halophyte types are saltworts (Salicornia spp.), orache or saltbush (Atriplex spp.), and goosefoot (Chenopodiaceae spp.). Tulips are also represented here.
Despite the harsh conditions, the lowland desert ecosystem supports an assortment of fauna, particularly small to moderate-size mammals that include various cat groups, antelope, jackal, rodents, and other animals that typically occupy dry temperate wastelands. The grass and low vegetation particularly allow grazing by wild and domesticated herbivores; the region is also home to reptiles, whether vegetarian or omnivorous.
Multitudes of avian flocks winter here, mainly in close proximity to the Caspian Sea; these include massed migratory formations of coot (Fulica atra), Sandwich tern (Thalasseus sandvicensis), and flamingo (Phoenicopterus roseus). Among the predatory birds recorded here are the eastern imperial eagle (Aquila heliaca) and white-tailed eagle (Haliaeetus albicilla).
Human Interaction
This ecosystem is viewed as a viable economic resource because the region supports livestock grazing, salt mining, and petroleum exploitation. The indigenous inhabitants view each of these activities as a necessity for sustainability, due to the constraints imposed by the harshness of the environment, which inhibits extensive development. However, each activity also imposes stress on this delicate ecosystem. Sheep and cattle commonly overgraze in ecosystems where precipitation is limited, because food supplies are of poor quality or scarce. This often causes grazers to consume and destroy even the root systems of the plants they forage. Consequently, natural food sources diminish with time, inducing further stress on both the ecosystem and those that use it.
Similarly, salt mining may alter the landscape for long periods because the limited precipitation impedes the process of plant reestablishment and succession even when it is supported by restorative efforts. Likewise, tailings from underground mining of locally occurring salt domes enter soil, surface water, and aquifer systems if the wastes are not properly managed. Further, the highly soluble salts migrate extensively and have wide-ranging effects on surrounding freshwater systems.
The Caspian lowland desert is susceptible to damage from accidental petroleum spillage. Some petroleum additives are soluble and miscible in water, and will severely damage potable water supplies. Further, the drilling and support activity tends to disrupt fragile vegetation networks in the desert soils. The costs of recovering spilled petroleum and restoring affected regions within this ecosystem could surpass the economic benefits derived from petroleum exploration.
The Caspian lowland desert is expected to expand, as global warming affects this region and the Caspian Sea level decreases. However, this is predicted to come at the cost of lowered biodiversity, as relatively rapid changes in average temperature, seasonality of precipitation, and extreme weather events combine with man-made pollution to fragment the existing habitat web.
Careful planning and exhaustive cost-risk-benefit analyses of the effects of tapping the region's natural resources—and counterbalancing the negative effects of climate change—will ultimately affect the short- and long-term quality and sustainability of this ecosystem.
Bibliography
Abdelly, C., M. Ozturk, M. Ashraf, and C. Grignon, eds. Biosaline Agriculture and High Salinity Tolerance. Birkhauser, 2008.
“Caspian Lowland Desert.” One Earth, www.oneearth.org/ecoregions/caspian-lowland-desert/. Accessed 31 Oct. 2024.
Dumont, H. J. “The Caspian Lake: History, Biota, Structure, and Function.” Limnology and Oceanography 43, no. 1, 1998.
Firouz, E. The Complete Fauna of Iran. I. B. Tauris & Co., 2005.
Ryabogina, N.E. "Peat Palaeorecords from the Arid Caspian Lowland in Russia: Environmental and Anthropogenic Effects During the Second Half of the Holocene." Quarterly Science Review, vol. 280, 15 Mar. 2022, doi.org/10.1016/j.quascirev.2022.107417. Accessed 25 July 2022.
Samant, Rohit, and Matthias Prange. "Climate-Driven 21st Century Caspian Sea Level Decline Estimated from CMIP6 Projections." Communications Earth & Environment, vol. 4, no. 1, 2023, pp. 1-12. doi.org/10.1038/s43247-023-01017-8. Accessed 1 Nov. 2024.
Savinova, S. V., et al. “Current Climate Conditions within Semi-Arid Rangelands of the Caspian Lowland Desert.” IOP Conference Series: Earth and Environmental Science, vol. 579, 2020. IOP Publishing Ltd., doi:10.1088/1755-1315/579/1/012009. Accessed 31 Oct. 2024.
Zehzad, B., B. H. Kiabi, and H. Madjnoonian. “The Natural Areas and Landscape of Iran: An Overview.” Zoology in the Middle East 26, no. 7–10, 2002.