ausblenden:
Schlagwörter:
Multi-Decadal Satellite
Zusammenfassung:
A large portion of Iran is characterized by arid and semi-arid climates, making the region inherently vulnerable to environmental stress. Over the past five decades, this vulnerability has been significantly exacerbated by a combination of climate-change related natural factors and human-driven activities, including unsustainable agricultural practices, deforestation, and inefficient irrigation. Additionally, Iran’s over-reliance on groundwater resources has led to the over-extraction of aquifers and widespread land subsidence. Together, these factors are pushing the country towards a severe environmental crisis, evidenced by diminished agricultural sustainability, depletion of water resources, and loss of biodiversity.
While these issues have been recognized for some time, the spatial and temporal specifics of their progression have yet to be comprehensively analyzed on a national scale. This study presents the results of our investigation, which integrates multi-decadal satellite data and field surveys to explore and quantify the interconnections between unsustainable groundwater extraction, aquifer depletion, surface water diversion, and desertification across Iran.
In recent decades, the country’s heavy reliance on groundwater for agricultural, industrial, and domestic use has led to a dramatic decline in groundwater levels and significant land subsidence. Our multi-decadal analysis of satellite data from various Synthetic Aperture Radar (SAR) sensors— including ERS, Envisat, ALOS, and Sentinel-1— reveals that approximately 56,000 km² (3.5%) of Iran is experiencing severe land subsidence, with certain areas sinking at alarming rates exceeding 35 cm per year. Recent surveys using Sentinel-1 data indicate that around 3,000 km² of land is subsiding at rates greater than 10 cm per year, underscoring the scale of the crisis.
We also conducted a spatiotemporal analysis of vegetation growth in relation to hydrometeorological factors across the country, using a variety of Earth Observation data, including MODIS, Sentinel-1/2, GRACE/FO, and ERA5-Land. This analysis aimed to assess the impact of irrigation practices and their relationship to water availability for sustainable development. Despite facing hydrometeorological water scarcity, Iran has seen an agricultural expansion of approximately 27,000 km² (9%) between 1992 and 2019, accompanied by the intensification of cultivation within existing agricultural areas. This is reflected in significant positive vegetation trends in 28% of the country’s croplands (around 48,000 km²), highlighting the central role of agriculture as the primary driver of groundwater depletion, water scarcity, and land subsidence.
The impact of groundwater depletion and running water disturbances also affects natural vegetation in playa and wetland ecosystems. This causes degradation of natural vegetation and emission of dust in most of the formerly permanent wetlands and associated steppes and loss of rare and endemic species. Dramatic cases have been documented in Turkman-Sahra (Golestan Province), Meyghan wetlands (Markazi Province), Tashk and Bakhtegan Wetlands (Fars Province). The halophytes and hygrohalophytes are highly sensitive to low changes of soil moisture and underground water level are largely threatened and even completely disappeared in recent years. Our findings highlight the importance of a multi-scale approach for effective water management in arid regions for creating resilient systems that support sustainable development from existing water resources.
